Merge all three apps into one repository

49 files changed, 2875 insertions, 0 deletions

diff --git a/cashier/.gitignore b/cashier/.gitignore
new file mode 100644
index 0000000..796b96d
--- /dev/null
+++ b/cashier/.gitignore
@@ -0,0 +1 @@
+/build
diff --git a/cashier/.gitlab-ci.yml b/cashier/.gitlab-ci.yml
new file mode 100644
index 0000000..f8cc7f3
--- /dev/null
+++ b/cashier/.gitlab-ci.yml
@@ -0,0 +1,35 @@
+image: registry.gitlab.com/fdroid/ci-images-client:latest
+
+cashier_test:
+  stage: test
+  only:
+    changes:
+      - "cashier"
+  script: ./gradlew :cashier:lint :cashier:assembleRelease
+
+cashier_deploy_nightly:
+  stage: deploy
+  only:
+    refs:
+      - master
+    changes:
+      - "cashier"
+  script:
+    # Ensure that key exists
+    - test -z "$DEBUG_KEYSTORE" && exit 0
+    # Rename nightly app
+    - sed -i
+        's,<string name="app_name">.*</string>,<string name="app_name">Cashier Nightly</string>,'
+        cashier/src/main/res/values*/strings.xml
+    # Set time-based version code
+    - export versionCode=$(date '+%s')
+    - sed -i "s,^\(\s*versionCode\) *[0-9].*,\1 $versionCode," cashier/build.gradle
+    # Set nightly application ID
+    - sed -i "s,^\(\s*applicationId\) \"*[a-z\.].*\",\1 \"net.taler.cashier.nightly\"," cashier/build.gradle
+    # Build the APK
+    - ./gradlew :cashier:assembleDebug
+    # START only needed while patch not accepted/released upstream
+    - apt update && apt install patch
+    - patch /usr/lib/python3/dist-packages/fdroidserver/nightly.py nightly-stats.patch
+    # END
+    - CI_PROJECT_URL="https://gitlab.com/gnu-taler/fdroid-repo" CI_PROJECT_PATH="gnu-taler/fdroid-repo" fdroid nightly -v
diff --git a/cashier/README.md b/cashier/README.md
new file mode 100644
index 0000000..e884f25
--- /dev/null
+++ b/cashier/README.md
@@ -0,0 +1,10 @@
+# GNU Taler Cashier App
+
+The purpose of this app is to enable people (a cashier) to take cash and give out e-cash.
+
+## Building
+
+You can import the project into Android Studio
+or build it with Gradle on the command line:
+
+    $ ./gradlew build
diff --git a/cashier/build.gradle b/cashier/build.gradle
new file mode 100644
index 0000000..5915f8a
--- /dev/null
+++ b/cashier/build.gradle
@@ -0,0 +1,72 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
+apply plugin: 'androidx.navigation.safeargs.kotlin'
+
+android {
+    compileSdkVersion 29
+    buildToolsVersion "29.0.3"
+
+    defaultConfig {
+        applicationId "net.taler.cashier"
+        minSdkVersion 23
+        targetSdkVersion 29
+        versionCode 1
+        versionName "0.1"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.core:core-ktx:1.2.0'
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    implementation 'androidx.security:security-crypto:1.0.0-alpha02'
+    implementation 'com.google.android.material:material:1.1.0'
+
+    implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
+    implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
+
+    // ViewModel and LiveData
+    def lifecycle_version = "2.2.0"
+    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
+
+    // QR codes
+    implementation 'com.google.zxing:core:3.4.0'
+
+    implementation "com.squareup.okhttp3:okhttp:3.12.6"
+
+    testImplementation 'junit:junit:4.13'
+
+    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
+}
diff --git a/cashier/lint.xml b/cashier/lint.xml
new file mode 100644
index 0000000..164e244
--- /dev/null
+++ b/cashier/lint.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<lint>
+
+</lint>
diff --git a/cashier/proguard-rules.pro b/cashier/proguard-rules.pro
new file mode 100644
index 0000000..f1b4245
--- /dev/null
+++ b/cashier/proguard-rules.pro
@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile
diff --git a/cashier/src/main/AndroidManifest.xml b/cashier/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..345c9a1
--- /dev/null
+++ b/cashier/src/main/AndroidManifest.xml
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    package="net.taler.cashier">
+
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.NFC" />
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:fullBackupContent="@xml/backup_descriptor"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme"
+        android:roundIcon="@mipmap/ic_launcher"
+        tools:ignore="GoogleAppIndexingWarning">
+
+        <activity
+            android:name=".MainActivity"
+            android:label="@string/app_name"
+            android:theme="@style/AppTheme.NoActionBar">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+    </application>
+
+</manifest>
diff --git a/cashier/src/main/ic_launcher-web.png b/cashier/src/main/ic_launcher-web.png
new file mode 100644
index 0000000..04a58c6
--- /dev/null
+++ b/cashier/src/main/ic_launcher-web.png
diff --git a/cashier/src/main/java/net/taler/cashier/Amount.kt b/cashier/src/main/java/net/taler/cashier/Amount.kt
new file mode 100644
index 0000000..2c237c8
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/Amount.kt
@@ -0,0 +1,45 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+data class Amount(val currency: String, val amount: String) {
+
+    companion object {
+
+        private val SIGNED_REGEX = Regex("""([+\-])(\w+):([0-9.]+)""")
+
+        @Suppress("unused")
+        fun fromString(strAmount: String): Amount {
+            val components = strAmount.split(":")
+            return Amount(components[0], components[1])
+        }
+
+        fun fromStringSigned(strAmount: String): Amount? {
+            val groups = SIGNED_REGEX.matchEntire(strAmount)?.groupValues ?: emptyList()
+            if (groups.size < 4) return null
+            var amount = groups[3].toDoubleOrNull() ?: return null
+            if (groups[1] == "-") amount *= -1
+            val currency = groups[2]
+            val amountStr = amount.toString()
+            // only display as many digits as required to precisely render the balance
+            return Amount(currency, amountStr.removeSuffix(".0"))
+        }
+    }
+
+    override fun toString() = "$amount $currency"
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt b/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt
new file mode 100644
index 0000000..b3a0221
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt
@@ -0,0 +1,182 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.annotation.SuppressLint
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.Menu
+import android.view.MenuInflater
+import android.view.MenuItem
+import android.view.View
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.view.inputmethod.EditorInfo
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.Observer
+import androidx.navigation.fragment.findNavController
+import kotlinx.android.synthetic.main.fragment_balance.*
+import net.taler.cashier.BalanceFragmentDirections.Companion.actionBalanceFragmentToTransactionFragment
+import net.taler.cashier.withdraw.LastTransaction
+import net.taler.cashier.withdraw.WithdrawStatus
+
+sealed class BalanceResult {
+    object Error : BalanceResult()
+    object Offline : BalanceResult()
+    class Success(val amount: Amount) : BalanceResult()
+}
+
+class BalanceFragment : Fragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+    private val withdrawManager by lazy { viewModel.withdrawManager }
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        setHasOptionsMenu(true)
+        return inflater.inflate(R.layout.fragment_balance, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        withdrawManager.lastTransaction.observe(viewLifecycleOwner, Observer { lastTransaction ->
+            onLastTransaction(lastTransaction)
+        })
+        viewModel.balance.observe(viewLifecycleOwner, Observer { result ->
+            when (result) {
+                is BalanceResult.Success -> onBalanceUpdated(result.amount)
+                else -> onBalanceUpdated(null, result is BalanceResult.Offline)
+            }
+        })
+        button5.setOnClickListener { onAmountButtonPressed(5) }
+        button10.setOnClickListener { onAmountButtonPressed(10) }
+        button20.setOnClickListener { onAmountButtonPressed(20) }
+        button50.setOnClickListener { onAmountButtonPressed(50) }
+
+        if (savedInstanceState != null) {
+            amountView.editText!!.setText(savedInstanceState.getCharSequence("amountView"))
+        }
+        amountView.editText!!.setOnEditorActionListener { _, actionId, _ ->
+            if (actionId == EditorInfo.IME_ACTION_GO) {
+                onAmountConfirmed(getAmountFromView())
+                true
+            } else false
+        }
+        viewModel.currency.observe(viewLifecycleOwner, Observer { currency ->
+            currencyView.text = currency
+        })
+        confirmWithdrawalButton.setOnClickListener { onAmountConfirmed(getAmountFromView()) }
+    }
+
+    override fun onStart() {
+        super.onStart()
+        // update balance if there's a config
+        if (viewModel.hasConfig()) {
+            viewModel.getBalance()
+        }
+    }
+
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        // for some reason automatic restore isn't working at the moment!?
+        amountView?.editText?.text.let {
+            outState.putCharSequence("amountView", it)
+        }
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.balance, menu)
+        super.onCreateOptionsMenu(menu, inflater)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem) = when (item.itemId) {
+        R.id.action_reconfigure -> {
+            findNavController().navigate(viewModel.configDestination)
+            true
+        }
+        R.id.action_lock -> {
+            viewModel.lock()
+            findNavController().navigate(viewModel.configDestination)
+            true
+        }
+        else -> super.onOptionsItemSelected(item)
+    }
+
+    private fun onBalanceUpdated(amount: Amount?, isOffline: Boolean = false) {
+        val uiList = listOf(
+            introView,
+            button5, button10, button20, button50,
+            amountView, currencyView, confirmWithdrawalButton
+        )
+        if (amount == null) {
+            balanceView.text =
+                getString(if (isOffline) R.string.balance_offline else R.string.balance_error)
+            uiList.forEach { it.fadeOut() }
+        } else {
+            @SuppressLint("SetTextI18n")
+            balanceView.text = "${amount.amount} ${amount.currency}"
+            uiList.forEach { it.fadeIn() }
+        }
+        progressBar.fadeOut()
+    }
+
+    private fun onAmountButtonPressed(amount: Int) {
+        amountView.editText!!.setText(amount.toString())
+        amountView.error = null
+    }
+
+    private fun getAmountFromView(): Int {
+        val str = amountView.editText!!.text.toString()
+        if (str.isBlank()) return 0
+        return Integer.parseInt(str)
+    }
+
+    private fun onAmountConfirmed(amount: Int) {
+        if (amount <= 0) {
+            amountView.error = getString(R.string.withdraw_error_zero)
+        } else if (!withdrawManager.hasSufficientBalance(amount)) {
+            amountView.error = getString(R.string.withdraw_error_insufficient_balance)
+        } else {
+            amountView.error = null
+            withdrawManager.withdraw(amount)
+            actionBalanceFragmentToTransactionFragment().let {
+                findNavController().navigate(it)
+            }
+        }
+    }
+
+    private fun onLastTransaction(lastTransaction: LastTransaction?) {
+        val status = lastTransaction?.withdrawStatus
+        val text = when (status) {
+            is WithdrawStatus.Success -> getString(
+                R.string.transaction_last_success, lastTransaction.withdrawAmount
+            )
+            is WithdrawStatus.Aborted -> getString(R.string.transaction_last_aborted)
+            else -> getString(R.string.transaction_last_error)
+        }
+        lastTransactionView.text = text
+        val drawable = if (status == WithdrawStatus.Success)
+            R.drawable.ic_check_circle
+        else
+            R.drawable.ic_error
+        lastTransactionView.setCompoundDrawablesRelativeWithIntrinsicBounds(drawable, 0, 0, 0)
+        lastTransactionView.visibility = VISIBLE
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/ConfigFragment.kt b/cashier/src/main/java/net/taler/cashier/ConfigFragment.kt
new file mode 100644
index 0000000..b9a97e5
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/ConfigFragment.kt
@@ -0,0 +1,139 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.os.Bundle
+import android.text.method.LinkMovementMethod
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.view.inputmethod.InputMethodManager
+import androidx.core.content.ContextCompat.getSystemService
+import androidx.core.text.HtmlCompat
+import androidx.core.text.HtmlCompat.FROM_HTML_MODE_LEGACY
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.Observer
+import androidx.navigation.fragment.findNavController
+import com.google.android.material.snackbar.Snackbar
+import com.google.android.material.snackbar.Snackbar.LENGTH_LONG
+import kotlinx.android.synthetic.main.fragment_config.*
+
+private const val URL_BANK_TEST = "https://bank.test.taler.net"
+private const val URL_BANK_TEST_REGISTER = "$URL_BANK_TEST/accounts/register"
+
+class ConfigFragment : Fragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_config, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        if (savedInstanceState == null) {
+            if (viewModel.config.bankUrl.isBlank()) {
+                urlView.editText!!.setText(URL_BANK_TEST)
+            } else {
+                urlView.editText!!.setText(viewModel.config.bankUrl)
+            }
+            usernameView.editText!!.setText(viewModel.config.username)
+            passwordView.editText!!.setText(viewModel.config.password)
+        } else {
+            urlView.editText!!.setText(savedInstanceState.getCharSequence("urlView"))
+            usernameView.editText!!.setText(savedInstanceState.getCharSequence("usernameView"))
+            passwordView.editText!!.setText(savedInstanceState.getCharSequence("passwordView"))
+        }
+        saveButton.setOnClickListener {
+            val config = Config(
+                bankUrl = urlView.editText!!.text.toString(),
+                username = usernameView.editText!!.text.toString(),
+                password = passwordView.editText!!.text.toString()
+            )
+            if (checkConfig(config)) {
+                // show progress
+                saveButton.visibility = INVISIBLE
+                progressBar.visibility = VISIBLE
+                // kick off check and observe result
+                viewModel.checkAndSaveConfig(config)
+                viewModel.configResult.observe(viewLifecycleOwner, onConfigResult)
+                // hide keyboard
+                val inputMethodManager =
+                    getSystemService(requireContext(), InputMethodManager::class.java)!!
+                inputMethodManager.hideSoftInputFromWindow(view.windowToken, 0)
+            }
+        }
+        demoView.text = HtmlCompat.fromHtml(
+            getString(R.string.config_demo_hint, URL_BANK_TEST_REGISTER), FROM_HTML_MODE_LEGACY
+        )
+        demoView.movementMethod = LinkMovementMethod.getInstance()
+    }
+
+    override fun onStart() {
+        super.onStart()
+        // focus on password if it is the only missing value (like after locking)
+        if (urlView.editText!!.text.isNotBlank()
+            && usernameView.editText!!.text.isNotBlank()
+            && passwordView.editText!!.text.isBlank()) {
+            passwordView.editText!!.requestFocus()
+        }
+    }
+
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        // for some reason automatic restore isn't working at the moment!?
+        outState.putCharSequence("urlView", urlView.editText?.text)
+        outState.putCharSequence("usernameView", usernameView.editText?.text)
+        outState.putCharSequence("passwordView", passwordView.editText?.text)
+    }
+
+    private fun checkConfig(config: Config): Boolean {
+        if (!config.bankUrl.startsWith("https://")) {
+            urlView.error = getString(R.string.config_bank_url_error)
+            urlView.requestFocus()
+            return false
+        }
+        if (config.username.isBlank()) {
+            usernameView.error = getString(R.string.config_username_error)
+            usernameView.requestFocus()
+            return false
+        }
+        urlView.isErrorEnabled = false
+        return true
+    }
+
+    private val onConfigResult = Observer<ConfigResult> { result ->
+        if (result == null) return@Observer
+        if (result.success) {
+            val action = ConfigFragmentDirections.actionConfigFragmentToBalanceFragment()
+            findNavController().navigate(action)
+        } else {
+            val res = if (result.authError) R.string.config_error_auth else R.string.config_error
+            Snackbar.make(view!!, res, LENGTH_LONG).show()
+        }
+        saveButton.visibility = VISIBLE
+        progressBar.visibility = INVISIBLE
+        viewModel.configResult.removeObservers(viewLifecycleOwner)
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/HttpHelper.kt b/cashier/src/main/java/net/taler/cashier/HttpHelper.kt
new file mode 100644
index 0000000..06b06db
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/HttpHelper.kt
@@ -0,0 +1,102 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.util.Log
+import androidx.annotation.WorkerThread
+import okhttp3.Credentials
+import okhttp3.MediaType
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okhttp3.RequestBody
+import org.json.JSONObject
+
+object HttpHelper {
+
+    private val TAG = HttpHelper::class.java.simpleName
+    private const val MIME_TYPE_JSON = "application/json"
+
+    @WorkerThread
+    fun makeJsonGetRequest(url: String, config: Config): HttpJsonResult {
+        val request = Request.Builder()
+            .addHeader("Accept", MIME_TYPE_JSON)
+            .url(url)
+            .get()
+            .build()
+        val response = try {
+            getHttpClient(config.username, config.password)
+            .newCall(request)
+            .execute()
+        } catch (e: Exception) {
+            Log.e(TAG, "Error retrieving $url", e)
+            return HttpJsonResult.Error(500)
+        }
+        return if (response.code() == 200 && response.body() != null) {
+            val jsonObject = JSONObject(response.body()!!.string())
+            HttpJsonResult.Success(jsonObject)
+        } else {
+            Log.e(TAG, "Received status ${response.code()} from $url expected 200")
+            HttpJsonResult.Error(response.code())
+        }
+    }
+
+    private val MEDIA_TYPE_JSON = MediaType.parse("$MIME_TYPE_JSON; charset=utf-8")
+
+    @WorkerThread
+    fun makeJsonPostRequest(url: String, body: String, config: Config): HttpJsonResult {
+        val request = Request.Builder()
+            .addHeader("Accept", MIME_TYPE_JSON)
+            .url(url)
+            .post(RequestBody.create(MEDIA_TYPE_JSON, body))
+            .build()
+        val response = try {
+            getHttpClient(config.username, config.password)
+                .newCall(request)
+                .execute()
+        } catch (e: Exception) {
+            Log.e(TAG, "Error retrieving $url", e)
+            return HttpJsonResult.Error(500)
+        }
+        return if (response.code() == 200 && response.body() != null) {
+            val jsonObject = JSONObject(response.body()!!.string())
+            HttpJsonResult.Success(jsonObject)
+        } else {
+            Log.e(TAG, "Received status ${response.code()} from $url expected 200")
+            HttpJsonResult.Error(response.code())
+        }
+    }
+
+    private fun getHttpClient(username: String, password: String) =
+        OkHttpClient.Builder().authenticator { _, response ->
+            val credential = Credentials.basic(username, password)
+            if (credential == response.request().header("Authorization")) {
+                // If we already failed with these credentials, don't retry
+                return@authenticator null
+            }
+            response
+                .request()
+                .newBuilder()
+                .header("Authorization", credential)
+                .build()
+        }.build()
+
+}
+
+sealed class HttpJsonResult {
+    class Error(val statusCode: Int) : HttpJsonResult()
+    class Success(val json: JSONObject) : HttpJsonResult()
+}
diff --git a/cashier/src/main/java/net/taler/cashier/MainActivity.kt b/cashier/src/main/java/net/taler/cashier/MainActivity.kt
new file mode 100644
index 0000000..b238054
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/MainActivity.kt
@@ -0,0 +1,62 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.content.Intent
+import android.content.Intent.*
+import android.os.Bundle
+import androidx.activity.viewModels
+import androidx.appcompat.app.AppCompatActivity
+import androidx.navigation.NavController
+import androidx.navigation.fragment.NavHostFragment
+import kotlinx.android.synthetic.main.activity_main.*
+
+class MainActivity : AppCompatActivity() {
+
+    private val viewModel: MainViewModel by viewModels()
+    private lateinit var nav: NavController
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+        setSupportActionBar(toolbar)
+        val navHostFragment =
+            supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
+        nav = navHostFragment.navController
+    }
+
+    override fun onStart() {
+        super.onStart()
+        if (!viewModel.hasConfig()) {
+            nav.navigate(viewModel.configDestination)
+        }
+    }
+
+    override fun onBackPressed() {
+        if (!viewModel.hasConfig() && nav.currentDestination?.id == R.id.configFragment) {
+            // we are in the configuration screen and need a config to continue
+            val intent = Intent(ACTION_MAIN).apply {
+                addCategory(CATEGORY_HOME)
+                flags = FLAG_ACTIVITY_NEW_TASK
+            }
+            startActivity(intent)
+        } else {
+            super.onBackPressed()
+        }
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/MainViewModel.kt b/cashier/src/main/java/net/taler/cashier/MainViewModel.kt
new file mode 100644
index 0000000..3874038
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/MainViewModel.kt
@@ -0,0 +1,148 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.annotation.SuppressLint
+import android.app.Application
+import android.util.Log
+import androidx.annotation.UiThread
+import androidx.annotation.WorkerThread
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.viewModelScope
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV
+import androidx.security.crypto.EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+import androidx.security.crypto.MasterKeys
+import androidx.security.crypto.MasterKeys.AES256_GCM_SPEC
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import net.taler.cashier.Amount.Companion.fromStringSigned
+import net.taler.cashier.HttpHelper.makeJsonGetRequest
+import net.taler.cashier.withdraw.WithdrawManager
+
+private val TAG = MainViewModel::class.java.simpleName
+
+private const val PREF_NAME = "net.taler.cashier.prefs"
+private const val PREF_KEY_BANK_URL = "bankUrl"
+private const val PREF_KEY_USERNAME = "username"
+private const val PREF_KEY_PASSWORD = "password"
+private const val PREF_KEY_CURRENCY = "currency"
+
+class MainViewModel(private val app: Application) : AndroidViewModel(app) {
+
+    val configDestination = ConfigFragmentDirections.actionGlobalConfigFragment()
+
+    private val masterKeyAlias = MasterKeys.getOrCreate(AES256_GCM_SPEC)
+    private val prefs = EncryptedSharedPreferences.create(
+        PREF_NAME, masterKeyAlias, app, AES256_SIV, AES256_GCM
+    )
+
+    internal var config = Config(
+        bankUrl = prefs.getString(PREF_KEY_BANK_URL, "")!!,
+        username = prefs.getString(PREF_KEY_USERNAME, "")!!,
+        password = prefs.getString(PREF_KEY_PASSWORD, "")!!
+    )
+
+    private val mCurrency = MutableLiveData<String>(
+        prefs.getString(PREF_KEY_CURRENCY, null)
+    )
+    internal val currency: LiveData<String> = mCurrency
+
+    private val mConfigResult = MutableLiveData<ConfigResult>()
+    val configResult: LiveData<ConfigResult> = mConfigResult
+
+    private val mBalance = MutableLiveData<BalanceResult>()
+    val balance: LiveData<BalanceResult> = mBalance
+
+    internal val withdrawManager = WithdrawManager(app, this)
+
+    fun hasConfig() = config.bankUrl.isNotEmpty()
+            && config.username.isNotEmpty()
+            && config.password.isNotEmpty()
+
+    /**
+     * Start observing [configResult] after calling this to get the result async.
+     * Warning: Ignore null results that are used to reset old results.
+     */
+    @UiThread
+    fun checkAndSaveConfig(config: Config) {
+        mConfigResult.value = null
+        viewModelScope.launch(Dispatchers.IO) {
+            val url = "${config.bankUrl}/accounts/${config.username}/balance"
+            Log.d(TAG, "Checking config: $url")
+            val result = when (val response = makeJsonGetRequest(url, config)) {
+                is HttpJsonResult.Success -> {
+                    val balance = response.json.getString("balance")
+                    val amount = fromStringSigned(balance)!!
+                    mCurrency.postValue(amount.currency)
+                    prefs.edit().putString(PREF_KEY_CURRENCY, amount.currency).apply()
+                    // save config
+                    saveConfig(config)
+                    ConfigResult(true)
+                }
+                is HttpJsonResult.Error -> {
+                    val authError = response.statusCode == 401
+                    ConfigResult(false, authError)
+                }
+            }
+            mConfigResult.postValue(result)
+        }
+    }
+
+    @WorkerThread
+    @SuppressLint("ApplySharedPref")
+    private fun saveConfig(config: Config) {
+        this.config = config
+        prefs.edit()
+            .putString(PREF_KEY_BANK_URL, config.bankUrl)
+            .putString(PREF_KEY_USERNAME, config.username)
+            .putString(PREF_KEY_PASSWORD, config.password)
+            .commit()
+    }
+
+    fun getBalance() = viewModelScope.launch(Dispatchers.IO) {
+        check(hasConfig()) { "No config to get balance" }
+        val url = "${config.bankUrl}/accounts/${config.username}/balance"
+        Log.d(TAG, "Checking balance at $url")
+        val result = when (val response = makeJsonGetRequest(url, config)) {
+            is HttpJsonResult.Success -> {
+                val balance = response.json.getString("balance")
+                fromStringSigned(balance)?.let { BalanceResult.Success(it) } ?: BalanceResult.Error
+            }
+            is HttpJsonResult.Error -> {
+                if (app.isOnline()) BalanceResult.Error
+                else BalanceResult.Offline
+            }
+        }
+        mBalance.postValue(result)
+    }
+
+    fun lock() {
+        saveConfig(config.copy(password = ""))
+    }
+
+}
+
+data class Config(
+    val bankUrl: String,
+    val username: String,
+    val password: String
+)
+
+class ConfigResult(val success: Boolean, val authError: Boolean = false)
diff --git a/cashier/src/main/java/net/taler/cashier/Utils.kt b/cashier/src/main/java/net/taler/cashier/Utils.kt
new file mode 100644
index 0000000..62f7a77
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/Utils.kt
@@ -0,0 +1,91 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier
+
+import android.content.Context
+import android.content.Context.CONNECTIVITY_SERVICE
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET
+import android.os.Build.VERSION.SDK_INT
+import android.view.View
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+
+object Utils {
+
+    private const val HEX_CHARS = "0123456789ABCDEF"
+
+    fun hexStringToByteArray(data: String): ByteArray {
+        val result = ByteArray(data.length / 2)
+
+        for (i in data.indices step 2) {
+            val firstIndex = HEX_CHARS.indexOf(data[i])
+            val secondIndex = HEX_CHARS.indexOf(data[i + 1])
+
+            val octet = firstIndex.shl(4).or(secondIndex)
+            result[i.shr(1)] = octet.toByte()
+        }
+        return result
+    }
+
+
+    private val HEX_CHARS_ARRAY = HEX_CHARS.toCharArray()
+
+    @Suppress("unused")
+    fun toHex(byteArray: ByteArray): String {
+        val result = StringBuffer()
+
+        byteArray.forEach {
+            val octet = it.toInt()
+            val firstIndex = (octet and 0xF0).ushr(4)
+            val secondIndex = octet and 0x0F
+            result.append(HEX_CHARS_ARRAY[firstIndex])
+            result.append(HEX_CHARS_ARRAY[secondIndex])
+        }
+        return result.toString()
+    }
+
+}
+
+fun View.fadeIn(endAction: () -> Unit = {}) {
+    if (visibility == VISIBLE) return
+    alpha = 0f
+    visibility = VISIBLE
+    animate().alpha(1f).withEndAction {
+        endAction.invoke()
+    }.start()
+}
+
+fun View.fadeOut(endAction: () -> Unit = {}) {
+    if (visibility == INVISIBLE) return
+    animate().alpha(0f).withEndAction {
+        visibility = INVISIBLE
+        alpha = 1f
+        endAction.invoke()
+    }.start()
+}
+
+fun Context.isOnline(): Boolean {
+    val cm = getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager
+    return if (SDK_INT < 29) {
+        @Suppress("DEPRECATION")
+        cm.activeNetworkInfo?.isConnected == true
+    } else {
+        val capabilities = cm.getNetworkCapabilities(cm.activeNetwork) ?: return false
+        capabilities.hasCapability(NET_CAPABILITY_INTERNET)
+    }
+}
diff --git a/cashier/src/main/java/net/taler/cashier/withdraw/ErrorFragment.kt b/cashier/src/main/java/net/taler/cashier/withdraw/ErrorFragment.kt
new file mode 100644
index 0000000..ceffcec
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/withdraw/ErrorFragment.kt
@@ -0,0 +1,55 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier.withdraw
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.Observer
+import androidx.navigation.fragment.findNavController
+import kotlinx.android.synthetic.main.fragment_error.*
+import net.taler.cashier.MainViewModel
+import net.taler.cashier.R
+
+class ErrorFragment : Fragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+    private val withdrawManager by lazy { viewModel.withdrawManager }
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_error, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        withdrawManager.withdrawStatus.observe(viewLifecycleOwner, Observer { status ->
+            if (status is WithdrawStatus.Aborted) {
+                textView.setText(R.string.transaction_aborted)
+            }
+        })
+        withdrawManager.completeTransaction()
+        backButton.setOnClickListener {
+            findNavController().popBackStack()
+        }
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/withdraw/NfcManager.kt b/cashier/src/main/java/net/taler/cashier/withdraw/NfcManager.kt
new file mode 100644
index 0000000..a487b5f
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/withdraw/NfcManager.kt
@@ -0,0 +1,234 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier.withdraw
+
+import android.app.Activity
+import android.content.Context
+import android.nfc.NfcAdapter
+import android.nfc.NfcAdapter.FLAG_READER_NFC_A
+import android.nfc.NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK
+import android.nfc.NfcAdapter.getDefaultAdapter
+import android.nfc.Tag
+import android.nfc.tech.IsoDep
+import android.util.Log
+import net.taler.cashier.Utils.hexStringToByteArray
+import org.json.JSONObject
+import java.io.ByteArrayOutputStream
+import java.net.URL
+import javax.net.ssl.HttpsURLConnection
+
+@Suppress("unused")
+private const val TALER_AID = "A0000002471001"
+
+class NfcManager : NfcAdapter.ReaderCallback {
+
+    companion object {
+        const val TAG = "taler-merchant"
+
+        /**
+         * Returns true if NFC is supported and false otherwise.
+         */
+        fun hasNfc(context: Context): Boolean {
+            return getNfcAdapter(context) != null
+        }
+
+        /**
+         * Enables NFC reader mode. Don't forget to call [stop] afterwards.
+         */
+        fun start(activity: Activity, nfcManager: NfcManager) {
+            getNfcAdapter(activity)?.enableReaderMode(activity, nfcManager, nfcManager.flags, null)
+        }
+
+        /**
+         * Disables NFC reader mode. Call after [start].
+         */
+        fun stop(activity: Activity) {
+            getNfcAdapter(activity)?.disableReaderMode(activity)
+        }
+
+        private fun getNfcAdapter(context: Context): NfcAdapter? {
+            return getDefaultAdapter(context)
+        }
+    }
+
+    private val flags = FLAG_READER_NFC_A or FLAG_READER_SKIP_NDEF_CHECK
+
+    private var tagString: String? = null
+    private var currentTag: IsoDep? = null
+
+    fun setTagString(tagString: String) {
+        this.tagString = tagString
+    }
+
+    override fun onTagDiscovered(tag: Tag?) {
+
+        Log.v(TAG, "tag discovered")
+
+        val isoDep = IsoDep.get(tag)
+        isoDep.connect()
+
+        currentTag = isoDep
+
+        isoDep.transceive(apduSelectFile())
+
+        val tagString: String? = tagString
+        if (tagString != null) {
+            isoDep.transceive(apduPutTalerData(1, tagString.toByteArray()))
+        }
+
+        // FIXME: use better pattern for sleeps in between requests
+        // -> start with fast polling, poll more slowly if no requests are coming
+
+        while (true) {
+            try {
+                val reqFrame = isoDep.transceive(apduGetData())
+                if (reqFrame.size < 2) {
+                    Log.v(TAG, "request frame too small")
+                    break
+                }
+                val req = ByteArray(reqFrame.size - 2)
+                if (req.isEmpty()) {
+                    continue
+                }
+                reqFrame.copyInto(req, 0, 0, reqFrame.size - 2)
+                val jsonReq = JSONObject(req.toString(Charsets.UTF_8))
+                val reqId = jsonReq.getInt("id")
+                Log.v(TAG, "got request $jsonReq")
+                val jsonInnerReq = jsonReq.getJSONObject("request")
+                val method = jsonInnerReq.getString("method")
+                val urlStr = jsonInnerReq.getString("url")
+                Log.v(TAG, "url '$urlStr'")
+                Log.v(TAG, "method '$method'")
+                val url = URL(urlStr)
+                val conn: HttpsURLConnection = url.openConnection() as HttpsURLConnection
+                conn.setRequestProperty("Accept", "application/json")
+                conn.connectTimeout = 5000
+                conn.doInput = true
+                when (method) {
+                    "get" -> {
+                        conn.requestMethod = "GET"
+                    }
+                    "postJson" -> {
+                        conn.requestMethod = "POST"
+                        conn.doOutput = true
+                        conn.setRequestProperty("Content-Type", "application/json; utf-8")
+                        val body = jsonInnerReq.getString("body")
+                        conn.outputStream.write(body.toByteArray(Charsets.UTF_8))
+                    }
+                    else -> {
+                        throw Exception("method not supported")
+                    }
+                }
+                Log.v(TAG, "connecting")
+                conn.connect()
+                Log.v(TAG, "connected")
+
+                val statusCode = conn.responseCode
+                val tunnelResp = JSONObject()
+                tunnelResp.put("id", reqId)
+                tunnelResp.put("status", conn.responseCode)
+
+                if (statusCode == 200) {
+                    val stream = conn.inputStream
+                    val httpResp = stream.buffered().readBytes()
+                    tunnelResp.put("responseJson", JSONObject(httpResp.toString(Charsets.UTF_8)))
+                }
+
+                Log.v(TAG, "sending: $tunnelResp")
+
+                isoDep.transceive(apduPutTalerData(2, tunnelResp.toString().toByteArray()))
+            } catch (e: Exception) {
+                Log.v(TAG, "exception during NFC loop: $e")
+                break
+            }
+        }
+
+        isoDep.close()
+    }
+
+    private fun writeApduLength(stream: ByteArrayOutputStream, size: Int) {
+        when {
+            size == 0 -> {
+                // No size field needed!
+            }
+            size <= 255 -> // One byte size field
+                stream.write(size)
+            size <= 65535 -> {
+                stream.write(0)
+                // FIXME: is this supposed to be little or big endian?
+                stream.write(size and 0xFF)
+                stream.write((size ushr 8) and 0xFF)
+            }
+            else -> throw Error("payload too big")
+        }
+    }
+
+    private fun apduSelectFile(): ByteArray {
+        return hexStringToByteArray("00A4040007A0000002471001")
+    }
+
+    private fun apduPutData(payload: ByteArray): ByteArray {
+        val stream = ByteArrayOutputStream()
+
+        // Class
+        stream.write(0x00)
+
+        // Instruction 0xDA = put data
+        stream.write(0xDA)
+
+        // Instruction parameters
+        // (proprietary encoding)
+        stream.write(0x01)
+        stream.write(0x00)
+
+        writeApduLength(stream, payload.size)
+
+        stream.write(payload)
+
+        return stream.toByteArray()
+    }
+
+    private fun apduPutTalerData(talerInst: Int, payload: ByteArray): ByteArray {
+        val realPayload = ByteArrayOutputStream()
+        realPayload.write(talerInst)
+        realPayload.write(payload)
+        return apduPutData(realPayload.toByteArray())
+    }
+
+    private fun apduGetData(): ByteArray {
+        val stream = ByteArrayOutputStream()
+
+        // Class
+        stream.write(0x00)
+
+        // Instruction 0xCA = get data
+        stream.write(0xCA)
+
+        // Instruction parameters
+        // (proprietary encoding)
+        stream.write(0x01)
+        stream.write(0x00)
+
+        // Max expected response size, two
+        // zero bytes denotes 65536
+        stream.write(0x0)
+        stream.write(0x0)
+
+        return stream.toByteArray()
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/withdraw/QrCodeManager.kt b/cashier/src/main/java/net/taler/cashier/withdraw/QrCodeManager.kt
new file mode 100644
index 0000000..e3ffa92
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/withdraw/QrCodeManager.kt
@@ -0,0 +1,42 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier.withdraw
+
+import android.graphics.Bitmap
+import android.graphics.Bitmap.Config.RGB_565
+import android.graphics.Color.BLACK
+import android.graphics.Color.WHITE
+import com.google.zxing.BarcodeFormat.QR_CODE
+import com.google.zxing.qrcode.QRCodeWriter
+
+object QrCodeManager {
+
+    fun makeQrCode(text: String, size: Int = 256): Bitmap {
+        val qrCodeWriter = QRCodeWriter()
+        val bitMatrix = qrCodeWriter.encode(text, QR_CODE, size, size)
+        val height = bitMatrix.height
+        val width = bitMatrix.width
+        val bmp = Bitmap.createBitmap(width, height, RGB_565)
+        for (x in 0 until width) {
+            for (y in 0 until height) {
+                bmp.setPixel(x, y, if (bitMatrix.get(x, y)) BLACK else WHITE)
+            }
+        }
+        return bmp
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/withdraw/TransactionFragment.kt b/cashier/src/main/java/net/taler/cashier/withdraw/TransactionFragment.kt
new file mode 100644
index 0000000..8b782b0
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/withdraw/TransactionFragment.kt
@@ -0,0 +1,174 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier.withdraw
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import androidx.core.content.ContextCompat.getColor
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.Observer
+import androidx.navigation.fragment.findNavController
+import kotlinx.android.synthetic.main.fragment_transaction.*
+import net.taler.cashier.MainViewModel
+import net.taler.cashier.R
+import net.taler.cashier.fadeIn
+import net.taler.cashier.fadeOut
+import net.taler.cashier.withdraw.TransactionFragmentDirections.Companion.actionTransactionFragmentToBalanceFragment
+import net.taler.cashier.withdraw.TransactionFragmentDirections.Companion.actionTransactionFragmentToErrorFragment
+import net.taler.cashier.withdraw.WithdrawResult.Error
+import net.taler.cashier.withdraw.WithdrawResult.InsufficientBalance
+import net.taler.cashier.withdraw.WithdrawResult.Success
+
+class TransactionFragment : Fragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+    private val withdrawManager by lazy { viewModel.withdrawManager }
+    private val nfcManager = NfcManager()
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_transaction, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        withdrawManager.withdrawAmount.observe(viewLifecycleOwner, Observer { amount ->
+            amountView.text = amount
+        })
+        withdrawManager.withdrawResult.observe(viewLifecycleOwner, Observer { result ->
+            onWithdrawResultReceived(result)
+        })
+        withdrawManager.withdrawStatus.observe(viewLifecycleOwner, Observer { status ->
+            onWithdrawStatusChanged(status)
+        })
+
+        // change intro text depending on whether NFC is available or not
+        val hasNfc = NfcManager.hasNfc(requireContext())
+        val intro = if (hasNfc) R.string.transaction_intro_nfc else R.string.transaction_intro
+        introView.setText(intro)
+
+        cancelButton.setOnClickListener {
+            findNavController().popBackStack()
+        }
+    }
+
+    override fun onStart() {
+        super.onStart()
+        if (withdrawManager.withdrawResult.value is Success) {
+            NfcManager.start(requireActivity(), nfcManager)
+        }
+    }
+
+    override fun onStop() {
+        super.onStop()
+        NfcManager.stop(requireActivity())
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        if (!requireActivity().isChangingConfigurations) {
+            withdrawManager.abort()
+        }
+    }
+
+    private fun onWithdrawResultReceived(result: WithdrawResult?) {
+        if (result != null) {
+            progressBar.animate()
+                .alpha(0f)
+                .withEndAction { progressBar?.visibility = INVISIBLE }
+                .setDuration(750)
+                .start()
+        }
+        when (result) {
+            is InsufficientBalance -> {
+                val c = getColor(requireContext(), R.color.design_default_color_error)
+                introView.setTextColor(c)
+                introView.text = getString(R.string.withdraw_error_insufficient_balance)
+            }
+            is Error -> {
+                val c = getColor(requireContext(), R.color.design_default_color_error)
+                introView.setTextColor(c)
+                introView.text = result.msg
+            }
+            is Success -> {
+                // start NFC
+                nfcManager.setTagString(result.talerUri)
+                NfcManager.start(
+                    requireActivity(),
+                    nfcManager
+                )
+                // show QR code
+                qrCodeView.alpha = 0f
+                qrCodeView.animate()
+                    .alpha(1f)
+                    .withStartAction {
+                        qrCodeView.visibility = VISIBLE
+                        qrCodeView.setImageBitmap(result.qrCode)
+                    }
+                    .setDuration(750)
+                    .start()
+            }
+        }
+    }
+
+    private fun onWithdrawStatusChanged(status: WithdrawStatus?): Any = when (status) {
+        is WithdrawStatus.SelectionDone -> {
+            qrCodeView.fadeOut {
+                qrCodeView?.setImageResource(R.drawable.ic_arrow)
+                qrCodeView?.fadeIn()
+            }
+            introView.fadeOut {
+                introView?.text = getString(R.string.transaction_intro_scanned)
+                introView?.fadeIn {
+                    confirmButton?.isEnabled = true
+                    confirmButton?.setOnClickListener {
+                        withdrawManager.confirm(status.withdrawalId)
+                    }
+                }
+            }
+        }
+        is WithdrawStatus.Confirming -> {
+            confirmButton.isEnabled = false
+            qrCodeView.fadeOut()
+            progressBar.fadeIn()
+        }
+        is WithdrawStatus.Success -> {
+            withdrawManager.completeTransaction()
+            actionTransactionFragmentToBalanceFragment().let {
+                findNavController().navigate(it)
+            }
+        }
+        is WithdrawStatus.Aborted -> onError()
+        is WithdrawStatus.Error -> onError()
+        null -> {
+            // no-op
+        }
+    }
+
+    private fun onError() {
+        actionTransactionFragmentToErrorFragment().let {
+            findNavController().navigate(it)
+        }
+    }
+
+}
diff --git a/cashier/src/main/java/net/taler/cashier/withdraw/WithdrawManager.kt b/cashier/src/main/java/net/taler/cashier/withdraw/WithdrawManager.kt
new file mode 100644
index 0000000..4c618ac
--- /dev/null
+++ b/cashier/src/main/java/net/taler/cashier/withdraw/WithdrawManager.kt
@@ -0,0 +1,232 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.cashier.withdraw
+
+import android.app.Application
+import android.graphics.Bitmap
+import android.os.CountDownTimer
+import android.util.Log
+import androidx.annotation.UiThread
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.launch
+import net.taler.cashier.BalanceResult
+import net.taler.cashier.HttpHelper.makeJsonGetRequest
+import net.taler.cashier.HttpHelper.makeJsonPostRequest
+import net.taler.cashier.HttpJsonResult.Error
+import net.taler.cashier.HttpJsonResult.Success
+import net.taler.cashier.MainViewModel
+import net.taler.cashier.R
+import org.json.JSONObject
+import java.util.concurrent.TimeUnit.MINUTES
+import java.util.concurrent.TimeUnit.SECONDS
+
+private val TAG = WithdrawManager::class.java.simpleName
+
+private val INTERVAL = SECONDS.toMillis(1)
+private val TIMEOUT = MINUTES.toMillis(2)
+
+class WithdrawManager(
+    private val app: Application,
+    private val viewModel: MainViewModel
+) {
+    private val scope
+        get() = viewModel.viewModelScope
+
+    private val config
+        get() = viewModel.config
+
+    private val currency: String?
+        get() = viewModel.currency.value
+
+    private var withdrawStatusCheck: Job? = null
+
+    private val mWithdrawAmount = MutableLiveData<String>()
+    val withdrawAmount: LiveData<String> = mWithdrawAmount
+
+    private val mWithdrawResult = MutableLiveData<WithdrawResult>()
+    val withdrawResult: LiveData<WithdrawResult> = mWithdrawResult
+
+    private val mWithdrawStatus = MutableLiveData<WithdrawStatus>()
+    val withdrawStatus: LiveData<WithdrawStatus> = mWithdrawStatus
+
+    private val mLastTransaction = MutableLiveData<LastTransaction>()
+    val lastTransaction: LiveData<LastTransaction> = mLastTransaction
+
+    @UiThread
+    fun hasSufficientBalance(amount: Int): Boolean {
+        val balanceResult = viewModel.balance.value
+        if (balanceResult !is BalanceResult.Success) return false
+        val balanceStr = balanceResult.amount.amount
+        val balanceDouble = balanceStr.toDouble()
+        return amount <= balanceDouble
+    }
+
+    @UiThread
+    fun withdraw(amount: Int) {
+        check(amount > 0) { "Withdraw amount was <= 0" }
+        check(currency != null) { "Currency is null" }
+        mWithdrawResult.value = null
+        mWithdrawAmount.value = "$amount $currency"
+        scope.launch(Dispatchers.IO) {
+            val url = "${config.bankUrl}/accounts/${config.username}/withdrawals"
+            Log.d(TAG, "Starting withdrawal at $url")
+            val body = JSONObject(mapOf("amount" to "${currency}:${amount}")).toString()
+            when (val result = makeJsonPostRequest(url, body, config)) {
+                is Success -> {
+                    val talerUri = result.json.getString("taler_withdraw_uri")
+                    val withdrawResult = WithdrawResult.Success(
+                        id = result.json.getString("withdrawal_id"),
+                        talerUri = talerUri,
+                        qrCode = QrCodeManager.makeQrCode(talerUri)
+                    )
+                    mWithdrawResult.postValue(withdrawResult)
+                    timer.start()
+                }
+                is Error -> {
+                    val errorStr = app.getString(R.string.withdraw_error_fetch)
+                    mWithdrawResult.postValue(WithdrawResult.Error(errorStr))
+                }
+            }
+        }
+    }
+
+    private val timer: CountDownTimer = object : CountDownTimer(TIMEOUT, INTERVAL) {
+        override fun onTick(millisUntilFinished: Long) {
+            val result = withdrawResult.value
+            if (result is WithdrawResult.Success) {
+                // check for active jobs and only do one at a time
+                val hasActiveCheck = withdrawStatusCheck?.isActive ?: false
+                if (!hasActiveCheck) {
+                    withdrawStatusCheck = checkWithdrawStatus(result.id)
+                }
+            } else {
+                cancel()
+            }
+        }
+
+        override fun onFinish() {
+            abort()
+            mWithdrawStatus.postValue(WithdrawStatus.Error)
+            cancel()
+        }
+    }
+
+    private fun checkWithdrawStatus(withdrawalId: String) = scope.launch(Dispatchers.IO) {
+        val url = "${config.bankUrl}/accounts/${config.username}/withdrawals/${withdrawalId}"
+        Log.d(TAG, "Checking withdraw status at $url")
+        val response = makeJsonGetRequest(url, config)
+        if (response !is Success) return@launch  // ignore errors and continue trying
+        val oldStatus = mWithdrawStatus.value
+        when {
+            response.json.getBoolean("aborted") -> {
+                cancelWithdrawStatusCheck()
+                mWithdrawStatus.postValue(WithdrawStatus.Aborted)
+            }
+            response.json.getBoolean("confirmation_done") -> {
+                if (oldStatus !is WithdrawStatus.Success) {
+                    cancelWithdrawStatusCheck()
+                    mWithdrawStatus.postValue(WithdrawStatus.Success)
+                    viewModel.getBalance()
+                }
+            }
+            response.json.getBoolean("selection_done") -> {
+                // only update status, if there's none, yet
+                // so we don't re-notify or overwrite newer status info
+                if (oldStatus == null) {
+                    mWithdrawStatus.postValue(WithdrawStatus.SelectionDone(withdrawalId))
+                }
+            }
+        }
+    }
+
+    private fun cancelWithdrawStatusCheck() {
+        timer.cancel()
+        withdrawStatusCheck?.cancel()
+    }
+
+    /**
+     * Aborts the last [withdrawResult], if it exists und there is no [withdrawStatus].
+     * Otherwise this is a no-op.
+     */
+    @UiThread
+    fun abort() {
+        val result = withdrawResult.value
+        val status = withdrawStatus.value
+        if (result is WithdrawResult.Success && status == null) {
+            cancelWithdrawStatusCheck()
+            abort(result.id)
+        }
+    }
+
+    private fun abort(withdrawalId: String) = scope.launch(Dispatchers.IO) {
+        val url = "${config.bankUrl}/accounts/${config.username}/withdrawals/${withdrawalId}/abort"
+        Log.d(TAG, "Aborting withdrawal at $url")
+        makeJsonPostRequest(url, "", config)
+    }
+
+    @UiThread
+    fun confirm(withdrawalId: String) {
+        mWithdrawStatus.value = WithdrawStatus.Confirming
+        scope.launch(Dispatchers.IO) {
+            val url =
+                "${config.bankUrl}/accounts/${config.username}/withdrawals/${withdrawalId}/confirm"
+            Log.d(TAG, "Confirming withdrawal at $url")
+            when (val result = makeJsonPostRequest(url, "", config)) {
+                is Success -> {
+                    // no-op still waiting for [timer] to confirm our confirmation
+                }
+                is Error -> {
+                    Log.e(TAG, "Error confirming withdrawal. Status code: ${result.statusCode}")
+                    mWithdrawStatus.postValue(WithdrawStatus.Error)
+                }
+            }
+        }
+    }
+
+    @UiThread
+    fun completeTransaction() {
+        mLastTransaction.value = LastTransaction(withdrawAmount.value!!, withdrawStatus.value!!)
+        withdrawStatusCheck = null
+        mWithdrawAmount.value = null
+        mWithdrawResult.value = null
+        mWithdrawStatus.value = null
+    }
+
+}
+
+sealed class WithdrawResult {
+    object InsufficientBalance : WithdrawResult()
+    class Error(val msg: String) : WithdrawResult()
+    class Success(val id: String, val talerUri: String, val qrCode: Bitmap) : WithdrawResult()
+}
+
+sealed class WithdrawStatus {
+    object Error : WithdrawStatus()
+    object Aborted : WithdrawStatus()
+    class SelectionDone(val withdrawalId: String) : WithdrawStatus()
+    object Confirming : WithdrawStatus()
+    object Success : WithdrawStatus()
+}
+
+data class LastTransaction(
+    val withdrawAmount: String,
+    val withdrawStatus: WithdrawStatus
+)
diff --git a/cashier/src/main/res/drawable-w550dp/ic_arrow.xml b/cashier/src/main/res/drawable-w550dp/ic_arrow.xml
new file mode 100644
index 0000000..331ea06
--- /dev/null
+++ b/cashier/src/main/res/drawable-w550dp/ic_arrow.xml
@@ -0,0 +1,11 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:alpha="0.56"
+    android:tint="@color/green"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#000000"
+        android:pathData="M20,5.41 L18.59,4 7,15.59V9H5V19H15V17H8.41" />
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_arrow.xml b/cashier/src/main/res/drawable/ic_arrow.xml
new file mode 100644
index 0000000..d7578bd
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_arrow.xml
@@ -0,0 +1,11 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:alpha="0.56"
+    android:tint="@color/green"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#000000"
+        android:pathData="M5,5.41 L6.41,4 18,15.59V9h2V19H10v-2h6.59" />
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_check_circle.xml b/cashier/src/main/res/drawable/ic_check_circle.xml
new file mode 100644
index 0000000..d43d6ba
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_check_circle.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:alpha="0.56"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM10,17l-5,-5 1.41,-1.41L10,14.17l7.59,-7.59L19,8l-9,9z" />
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_clear.xml b/cashier/src/main/res/drawable/ic_clear.xml
new file mode 100644
index 0000000..f50fd99
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_clear.xml
@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M19,6.41L17.59,5 12,10.59 6.41,5 5,6.41 10.59,12 5,17.59 6.41,19 12,13.41 17.59,19 19,17.59 13.41,12z" />
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_error.xml b/cashier/src/main/res/drawable/ic_error.xml
new file mode 100644
index 0000000..b7e22a0
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_error.xml
@@ -0,0 +1,11 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:alpha="0.56"
+    android:tint="@color/red"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM13,17h-2v-2h2v2zM13,13h-2L11,7h2v6z" />
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_launcher_foreground.xml b/cashier/src/main/res/drawable/ic_launcher_foreground.xml
new file mode 100644
index 0000000..fbaac05
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_launcher_foreground.xml
@@ -0,0 +1,15 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="48"
+    android:viewportHeight="48">
+  <group
+      android:translateX="12"
+      android:translateY="12">
+    <path
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+        android:fillColor="#f9f9f9"
+        tools:ignore="VectorPath" />
+  </group>
+</vector>
diff --git a/cashier/src/main/res/drawable/ic_withdraw.xml b/cashier/src/main/res/drawable/ic_withdraw.xml
new file mode 100644
index 0000000..b694a2b
--- /dev/null
+++ b/cashier/src/main/res/drawable/ic_withdraw.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#000000"
+        android:pathData="M3 0V3H0V5H3V8H5V5H8V3H5V0H3M9 3V6H6V9H3V19C3 20.1 3.89 21 5 21H19C20.11 21 21 20.11 21 19V18H12C10.9 18 10 17.11 10 16V8C10 6.9 10.89 6 12 6H21V5C21 3.9 20.11 3 19 3H9M12 8V16H22V8H12M16 10.5C16.83 10.5 17.5 11.17 17.5 12C17.5 12.83 16.83 13.5 16 13.5C15.17 13.5 14.5 12.83 14.5 12C14.5 11.17 15.17 10.5 16 10.5Z" />
+</vector>
diff --git a/cashier/src/main/res/layout-w550dp/fragment_balance.xml b/cashier/src/main/res/layout-w550dp/fragment_balance.xml
new file mode 100644
index 0000000..d04698b
--- /dev/null
+++ b/cashier/src/main/res/layout-w550dp/fragment_balance.xml
@@ -0,0 +1,222 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".BalanceFragment">
+
+    <TextView
+        android:id="@+id/lastTransactionView"
+        style="@style/Widget.MaterialComponents.Snackbar.FullWidth"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:background="?attr/colorPrimaryDark"
+        android:drawableStart="@drawable/ic_check_circle"
+        android:drawablePadding="8dp"
+        android:drawableTint="?attr/colorOnPrimarySurface"
+        android:gravity="center_vertical"
+        android:padding="8dp"
+        android:textColor="?attr/colorOnPrimarySurface"
+        android:visibility="gone"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:text="@string/transaction_last_success"
+        tools:visibility="visible" />
+
+    <View
+        android:id="@+id/balanceBackground"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:background="@color/background"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/lastTransactionView" />
+
+    <TextView
+        android:id="@+id/balanceLabel"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="32dp"
+        android:layout_marginTop="32dp"
+        android:layout_marginEnd="32dp"
+        android:text="@string/balance_current_label"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        app:layout_constraintBottom_toTopOf="@+id/balanceView"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/lastTransactionView"
+        app:layout_constraintVertical_bias="0.0"
+        app:layout_constraintVertical_chainStyle="packed" />
+
+    <TextView
+        android:id="@+id/balanceView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:gravity="center"
+        android:textAppearance="@style/TextAppearance.AppCompat.Headline"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/balanceLabel"
+        tools:text="100 KUDOS" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="@+id/balanceView"
+        app:layout_constraintEnd_toEndOf="@+id/balanceView"
+        app:layout_constraintStart_toStartOf="@+id/balanceView"
+        app:layout_constraintTop_toTopOf="@+id/balanceView" />
+
+    <androidx.constraintlayout.widget.Guideline
+        android:id="@+id/guideline"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        app:layout_constraintGuide_percent="0.5" />
+
+    <TextView
+        android:id="@+id/introView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:text="@string/withdraw_into"
+        android:textAlignment="center"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="@+id/guideline"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button5"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="5"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toStartOf="@+id/button10"
+        app:layout_constraintHorizontal_chainStyle="packed"
+        app:layout_constraintStart_toStartOf="@+id/guideline"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button10"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="10"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toStartOf="@+id/button20"
+        app:layout_constraintStart_toEndOf="@+id/button5"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button20"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="20"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toStartOf="@+id/button50"
+        app:layout_constraintStart_toEndOf="@+id/button10"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button50"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="50"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@+id/button20"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/amountView"
+        style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:hint="@string/withdraw_input_amount"
+        android:visibility="invisible"
+        app:endIconDrawable="@drawable/ic_clear"
+        app:endIconMode="clear_text"
+        app:endIconTint="?attr/colorControlNormal"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="@+id/guideline"
+        app:layout_constraintTop_toBottomOf="@+id/button5"
+        tools:visibility="visible">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:ems="6"
+            android:imeOptions="actionGo"
+            android:inputType="number"
+            android:maxLength="4" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <TextView
+        android:id="@+id/currencyView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@+id/amountView"
+        app:layout_constraintTop_toTopOf="@+id/amountView"
+        tools:text="TESTKUDOS"
+        tools:visibility="visible" />
+
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/confirmWithdrawalButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:backgroundTint="@color/green"
+        android:drawableLeft="@drawable/ic_withdraw"
+        android:drawableTint="?attr/colorOnPrimarySurface"
+        android:text="@string/withdraw_button_confirm"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="@+id/guideline"
+        app:layout_constraintTop_toBottomOf="@+id/amountView"
+        app:layout_constraintVertical_bias="1.0"
+        tools:ignore="RtlHardcoded"
+        tools:visibility="visible" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/cashier/src/main/res/layout-w550dp/fragment_transaction.xml b/cashier/src/main/res/layout-w550dp/fragment_transaction.xml
new file mode 100644
index 0000000..610ed28
--- /dev/null
+++ b/cashier/src/main/res/layout-w550dp/fragment_transaction.xml
@@ -0,0 +1,111 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".withdraw.TransactionFragment">
+
+    <TextView
+        android:id="@+id/introView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:gravity="center_horizontal"
+        android:text="@string/transaction_intro"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <TextView
+        android:id="@+id/amountView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:gravity="center_horizontal"
+        android:textAppearance="@style/TextAppearance.AppCompat.Headline"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:text="50 KUDOS" />
+
+    <androidx.constraintlayout.widget.Guideline
+        android:id="@+id/guideline"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        app:layout_constraintGuide_percent="0.5" />
+
+    <ImageView
+        android:id="@+id/qrCodeView"
+        android:layout_width="256dp"
+        android:layout_height="256dp"
+        android:layout_margin="32dp"
+        android:keepScreenOn="true"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="@+id/guideline"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:ignore="ContentDescription"
+        tools:src="@drawable/ic_arrow"
+        tools:visibility="visible" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyleLarge"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="@+id/qrCodeView"
+        app:layout_constraintEnd_toEndOf="@+id/qrCodeView"
+        app:layout_constraintStart_toStartOf="@+id/qrCodeView"
+        app:layout_constraintTop_toTopOf="@+id/qrCodeView" />
+
+    <Button
+        android:id="@+id/cancelButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:backgroundTint="@color/red"
+        android:text="@string/transaction_abort"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/confirmButton"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintHorizontal_chainStyle="spread_inside"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/qrCodeView"
+        app:layout_constraintVertical_bias="1.0" />
+
+    <Button
+        android:id="@+id/confirmButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:backgroundTint="@color/green"
+        android:enabled="false"
+        android:text="@string/transaction_confirm"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/guideline"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toEndOf="@+id/cancelButton"
+        tools:enabled="true" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/cashier/src/main/res/layout/activity_main.xml b/cashier/src/main/res/layout/activity_main.xml
new file mode 100644
index 0000000..e41b842
--- /dev/null
+++ b/cashier/src/main/res/layout/activity_main.xml
@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".MainActivity">
+
+    <com.google.android.material.appbar.AppBarLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:theme="@style/AppTheme.AppBarOverlay">
+
+        <com.google.android.material.appbar.MaterialToolbar
+            android:id="@+id/toolbar"
+            style="@style/AppTheme.Toolbar"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content" />
+
+    </com.google.android.material.appbar.AppBarLayout>
+
+    <androidx.fragment.app.FragmentContainerView
+        android:id="@+id/nav_host_fragment"
+        android:name="androidx.navigation.fragment.NavHostFragment"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:defaultNavHost="true"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:navGraph="@navigation/nav_graph" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>
diff --git a/cashier/src/main/res/layout/fragment_balance.xml b/cashier/src/main/res/layout/fragment_balance.xml
new file mode 100644
index 0000000..5dafc59
--- /dev/null
+++ b/cashier/src/main/res/layout/fragment_balance.xml
@@ -0,0 +1,225 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".BalanceFragment">
+
+    <TextView
+        android:id="@+id/lastTransactionView"
+        style="@style/Widget.MaterialComponents.Snackbar.FullWidth"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:background="?attr/colorPrimaryDark"
+        android:drawableStart="@drawable/ic_check_circle"
+        android:drawablePadding="8dp"
+        android:drawableTint="?attr/colorOnPrimarySurface"
+        android:gravity="center_vertical"
+        android:padding="8dp"
+        android:textColor="?attr/colorOnPrimarySurface"
+        android:visibility="gone"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:text="@string/transaction_last_success"
+        tools:visibility="visible" />
+
+    <View
+        android:id="@+id/balanceBackground"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:background="@color/background"
+        app:layout_constraintBottom_toBottomOf="@+id/balanceView"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/lastTransactionView" />
+
+    <TextView
+        android:id="@+id/balanceLabel"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:text="@string/balance_current_label"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/lastTransactionView" />
+
+    <TextView
+        android:id="@+id/balanceView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:paddingStart="@dimen/default_margin"
+        android:paddingTop="8dp"
+        android:gravity="center"
+        android:paddingEnd="@dimen/default_margin"
+        android:paddingBottom="@dimen/default_margin"
+        android:textAppearance="@style/TextAppearance.AppCompat.Headline"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/balanceLabel"
+        tools:text="100 KUDOS" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="@+id/balanceView"
+        app:layout_constraintEnd_toEndOf="@+id/balanceView"
+        app:layout_constraintStart_toStartOf="@+id/balanceView"
+        app:layout_constraintTop_toTopOf="@+id/balanceView" />
+
+    <TextView
+        android:id="@+id/introView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="@dimen/default_margin"
+        android:layout_marginTop="32dp"
+        android:layout_marginEnd="@dimen/default_margin"
+        android:text="@string/withdraw_into"
+        android:textAlignment="center"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toTopOf="@+id/button5"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/balanceBackground"
+        app:layout_constraintVertical_bias="0.25"
+        app:layout_constraintVertical_chainStyle="packed"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button5"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="5"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toTopOf="@+id/amountView"
+        app:layout_constraintEnd_toStartOf="@+id/button10"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintHorizontal_chainStyle="packed"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button10"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="10"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toStartOf="@+id/button20"
+        app:layout_constraintStart_toEndOf="@+id/button5"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button20"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="20"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toStartOf="@+id/button50"
+        app:layout_constraintStart_toEndOf="@+id/button10"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button50"
+        style="@style/AmountButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="50"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@+id/button20"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:ignore="HardcodedText"
+        tools:visibility="visible" />
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/amountView"
+        style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="@dimen/default_margin"
+        android:layout_marginTop="@dimen/default_margin"
+        android:hint="@string/withdraw_input_amount"
+        android:visibility="invisible"
+        app:endIconDrawable="@drawable/ic_clear"
+        app:endIconMode="clear_text"
+        app:endIconTint="?attr/colorControlNormal"
+        app:layout_constraintBottom_toTopOf="@+id/confirmWithdrawalButton"
+        app:layout_constraintEnd_toStartOf="@+id/currencyView"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintHorizontal_chainStyle="packed"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/button5"
+        tools:visibility="visible">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:ems="6"
+            android:imeOptions="actionGo"
+            android:inputType="number"
+            android:maxLength="4" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <TextView
+        android:id="@+id/currencyView"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toEndOf="@+id/amountView"
+        app:layout_constraintTop_toTopOf="@+id/amountView"
+        tools:text="TESTKUDOS"
+        tools:visibility="visible" />
+
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/confirmWithdrawalButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:backgroundTint="@color/green"
+        android:drawableLeft="@drawable/ic_withdraw"
+        android:drawableTint="?attr/colorOnPrimarySurface"
+        android:text="@string/withdraw_button_confirm"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/amountView"
+        tools:ignore="RtlHardcoded"
+        tools:visibility="visible" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/cashier/src/main/res/layout/fragment_config.xml b/cashier/src/main/res/layout/fragment_config.xml
new file mode 100644
index 0000000..47ec6f9
--- /dev/null
+++ b/cashier/src/main/res/layout/fragment_config.xml
@@ -0,0 +1,112 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/urlView"
+        style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:hint="@string/config_bank_url"
+        app:endIconMode="clear_text"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="textUri" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/usernameView"
+        style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:hint="@string/config_username"
+        app:boxBackgroundMode="outline"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/urlView">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="text" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/passwordView"
+        style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:hint="@string/config_password"
+        app:boxBackgroundMode="outline"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/usernameView"
+        app:passwordToggleEnabled="true">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="textWebPassword" />
+
+    </com.google.android.material.textfield.TextInputLayout>
+
+    <Button
+        android:id="@+id/saveButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:text="@string/config_button_save"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/passwordView" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toBottomOf="@+id/saveButton"
+        app:layout_constraintEnd_toEndOf="@+id/saveButton"
+        app:layout_constraintStart_toStartOf="@+id/saveButton"
+        app:layout_constraintTop_toTopOf="@+id/saveButton"
+        tools:visibility="visible" />
+
+    <TextView
+        android:id="@+id/demoView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/default_margin"
+        android:text="@string/config_demo_hint"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/saveButton" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/cashier/src/main/res/layout/fragment_error.xml b/cashier/src/main/res/layout/fragment_error.xml
new file mode 100644
index 0000000..ac34c85
--- /dev/null
+++ b/cashier/src/main/res/layout/fragment_error.xml
@@ -0,0 +1,65 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/frameLayout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".withdraw.ErrorFragment">
+
+    <ImageView
+        android:id="@+id/imageView"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:layout_margin="32dp"
+        android:src="@drawable/ic_error"
+        app:layout_constraintBottom_toTopOf="@+id/textView"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:ignore="ContentDescription" />
+
+    <androidx.appcompat.widget.AppCompatTextView
+        android:id="@+id/textView"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:layout_margin="32dp"
+        android:text="@string/transaction_error"
+        android:textAlignment="center"
+        android:textColor="@color/red"
+        app:autoSizeMaxTextSize="42sp"
+        app:autoSizeTextType="uniform"
+        app:layout_constraintBottom_toTopOf="@+id/backButton"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+    <Button
+        android:id="@+id/backButton"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:text="@string/transaction_button_back"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/cashier/src/main/res/layout/fragment_transaction.xml b/cashier/src/main/res/layout/fragment_transaction.xml
new file mode 100644
index 0000000..3affbf2
--- /dev/null
+++ b/cashier/src/main/res/layout/fragment_transaction.xml
@@ -0,0 +1,100 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".withdraw.TransactionFragment">
+
+    <TextView
+        android:id="@+id/introView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:gravity="center_horizontal"
+        android:text="@string/transaction_intro"
+        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <TextView
+        android:id="@+id/amountView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="32dp"
+        android:gravity="center_horizontal"
+        android:textAppearance="@style/TextAppearance.AppCompat.Headline"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/introView"
+        tools:text="50 KUDOS" />
+
+    <ImageView
+        android:id="@+id/qrCodeView"
+        android:layout_width="256dp"
+        android:layout_height="256dp"
+        android:layout_margin="32dp"
+        android:keepScreenOn="true"
+        android:visibility="invisible"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/amountView"
+        tools:ignore="ContentDescription"
+        tools:src="@drawable/ic_arrow"
+        tools:visibility="visible" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyleLarge"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="@+id/qrCodeView"
+        app:layout_constraintEnd_toEndOf="@+id/qrCodeView"
+        app:layout_constraintStart_toStartOf="@+id/qrCodeView"
+        app:layout_constraintTop_toTopOf="@+id/qrCodeView" />
+
+    <Button
+        android:id="@+id/cancelButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:backgroundTint="@color/red"
+        android:text="@string/transaction_abort"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/confirmButton"
+        app:layout_constraintHorizontal_chainStyle="spread_inside"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/qrCodeView"
+        app:layout_constraintVertical_bias="1.0" />
+
+    <Button
+        android:id="@+id/confirmButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:backgroundTint="@color/green"
+        android:enabled="false"
+        android:text="@string/transaction_confirm"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@+id/cancelButton"
+        tools:enabled="true" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/cashier/src/main/res/menu/balance.xml b/cashier/src/main/res/menu/balance.xml
new file mode 100644
index 0000000..bc64af3
--- /dev/null
+++ b/cashier/src/main/res/menu/balance.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_reconfigure"
+        android:title="@string/action_reconfigure"
+        app:showAsAction="never" />
+    <item
+        android:id="@+id/action_lock"
+        android:title="@string/action_lock"
+        app:showAsAction="never" />
+
+</menu>
diff --git a/cashier/src/main/res/mipmap-anydpi-v26/ic_launcher.xml b/cashier/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
new file mode 100644
index 0000000..7353dbd
--- /dev/null
+++ b/cashier/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>
\ No newline at end of file
diff --git a/cashier/src/main/res/mipmap-hdpi/ic_launcher.png b/cashier/src/main/res/mipmap-hdpi/ic_launcher.png
new file mode 100644
index 0000000..c52928c
--- /dev/null
+++ b/cashier/src/main/res/mipmap-hdpi/ic_launcher.png
diff --git a/cashier/src/main/res/mipmap-mdpi/ic_launcher.png b/cashier/src/main/res/mipmap-mdpi/ic_launcher.png
new file mode 100644
index 0000000..b97178b
--- /dev/null
+++ b/cashier/src/main/res/mipmap-mdpi/ic_launcher.png
diff --git a/cashier/src/main/res/mipmap-xhdpi/ic_launcher.png b/cashier/src/main/res/mipmap-xhdpi/ic_launcher.png
new file mode 100644
index 0000000..8f92c07
--- /dev/null
+++ b/cashier/src/main/res/mipmap-xhdpi/ic_launcher.png
diff --git a/cashier/src/main/res/mipmap-xxhdpi/ic_launcher.png b/cashier/src/main/res/mipmap-xxhdpi/ic_launcher.png
new file mode 100644
index 0000000..214cbea
--- /dev/null
+++ b/cashier/src/main/res/mipmap-xxhdpi/ic_launcher.png
diff --git a/cashier/src/main/res/mipmap-xxxhdpi/ic_launcher.png b/cashier/src/main/res/mipmap-xxxhdpi/ic_launcher.png
new file mode 100644
index 0000000..b959cd3
--- /dev/null
+++ b/cashier/src/main/res/mipmap-xxxhdpi/ic_launcher.png
diff --git a/cashier/src/main/res/navigation/nav_graph.xml b/cashier/src/main/res/navigation/nav_graph.xml
new file mode 100644
index 0000000..49f8881
--- /dev/null
+++ b/cashier/src/main/res/navigation/nav_graph.xml
@@ -0,0 +1,73 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<navigation xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/nav_graph"
+    app:startDestination="@id/balanceFragment"
+    tools:ignore="UnusedNavigation">
+
+    <fragment
+        android:id="@+id/configFragment"
+        android:name="net.taler.cashier.ConfigFragment"
+        android:label="ConfigFragment"
+        tools:layout="@layout/fragment_config">
+        <action
+            android:id="@+id/action_configFragment_to_balanceFragment"
+            app:destination="@id/balanceFragment"
+            app:launchSingleTop="true"
+            app:popUpTo="@id/balanceFragment" />
+    </fragment>
+
+    <fragment
+        android:id="@+id/balanceFragment"
+        android:name="net.taler.cashier.BalanceFragment"
+        android:label="fragment_balance"
+        tools:layout="@layout/fragment_balance">
+        <action
+            android:id="@+id/action_balanceFragment_to_transactionFragment"
+            app:destination="@id/transactionFragment" />
+    </fragment>
+
+    <fragment
+        android:id="@+id/transactionFragment"
+        android:name="net.taler.cashier.withdraw.TransactionFragment"
+        android:label="fragment_transaction"
+        tools:layout="@layout/fragment_transaction">
+        <action
+            android:id="@+id/action_transactionFragment_to_errorFragment"
+            app:destination="@id/errorFragment"
+            app:launchSingleTop="true"
+            app:popUpTo="@+id/balanceFragment" />
+        <action
+            android:id="@+id/action_transactionFragment_to_balanceFragment"
+            app:destination="@id/balanceFragment"
+            app:launchSingleTop="true"
+            app:popUpTo="@+id/balanceFragment" />
+    </fragment>
+
+    <fragment
+        android:id="@+id/errorFragment"
+        android:name="net.taler.cashier.withdraw.ErrorFragment"
+        tools:layout="@layout/fragment_error" />
+
+    <action
+        android:id="@+id/action_global_configFragment"
+        app:destination="@id/configFragment"
+        app:launchSingleTop="true" />
+
+</navigation>
diff --git a/cashier/src/main/res/values-night/colors.xml b/cashier/src/main/res/values-night/colors.xml
new file mode 100644
index 0000000..55dde58
--- /dev/null
+++ b/cashier/src/main/res/values-night/colors.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<resources>
+    <color name="background">#222222</color>
+</resources>
diff --git a/cashier/src/main/res/values/colors.xml b/cashier/src/main/res/values/colors.xml
new file mode 100644
index 0000000..61338da
--- /dev/null
+++ b/cashier/src/main/res/values/colors.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#1565C0</color>
+    <color name="colorPrimaryDark">#6A1B9A</color>
+    <color name="colorAccent">#D81B60</color>
+
+    <color name="background">#F1F1F1</color>
+    <color name="green">#388E3C</color>
+    <color name="red">#D32F2F</color>
+</resources>
diff --git a/cashier/src/main/res/values/dimens.xml b/cashier/src/main/res/values/dimens.xml
new file mode 100644
index 0000000..9d9d85a
--- /dev/null
+++ b/cashier/src/main/res/values/dimens.xml
@@ -0,0 +1,3 @@
+<resources>
+    <dimen name="default_margin">16dp</dimen>
+</resources>
diff --git a/cashier/src/main/res/values/ic_launcher_background.xml b/cashier/src/main/res/values/ic_launcher_background.xml
new file mode 100644
index 0000000..3862264
--- /dev/null
+++ b/cashier/src/main/res/values/ic_launcher_background.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="ic_launcher_background">#1565C0</color>
+</resources>
\ No newline at end of file
diff --git a/cashier/src/main/res/values/strings.xml b/cashier/src/main/res/values/strings.xml
new file mode 100644
index 0000000..5df5bfa
--- /dev/null
+++ b/cashier/src/main/res/values/strings.xml
@@ -0,0 +1,39 @@
+<resources>
+    <string name="app_name">Taler Cashier</string>
+
+    <string name="config_bank_url">Bank API address</string>
+    <string name="config_username">Username</string>
+    <string name="config_password">Password</string>
+    <string name="config_button_save">Save</string>
+    <string name="config_bank_url_error">The address in invalid.</string>
+    <string name="config_username_error">Please enter your username</string>
+    <string name="config_error">Error retrieving configuration</string>
+    <string name="config_error_auth">Invalid username or password</string>
+    <string name="config_demo_hint">For testing, you can <![CDATA[<a href="%s">create a test account at the demo bank</a>]]>.</string>
+
+    <string name="balance_current_label">Current balance</string>
+    <string name="balance_error">ERROR</string>
+    <string name="balance_offline">Offline. Please connect to the Internet</string>
+    <string name="action_reconfigure">Reconfigure</string>
+    <string name="action_lock">Lock</string>
+
+    <string name="withdraw_input_amount">Amount</string>
+    <string name="withdraw_into">How much e-cash should be withdrawn?</string>
+    <string name="withdraw_error_zero">Enter positive amount</string>
+    <string name="withdraw_error_insufficient_balance">Insufficient balance</string>
+    <string name="withdraw_error_fetch">Error communicating with bank</string>
+    <string name="withdraw_button_confirm">Withdraw</string>
+
+    <string name="transaction_intro">Scan code\nwith the Taler wallet app\nto get</string>
+    <string name="transaction_intro_nfc">Scan code or use NFC\nwith the Taler wallet app\nto get</string>
+    <string name="transaction_intro_scanned">Please confirm the transaction!</string>
+    <string name="transaction_confirm">Confirm</string>
+    <string name="transaction_abort">Abort</string>
+    <string name="transaction_error">Transaction error</string>
+    <string name="transaction_aborted">Transaction aborted</string>
+    <string name="transaction_button_back">Go back</string>
+    <string name="transaction_last_success">Last Transaction: %s withdrawn</string>
+    <string name="transaction_last_aborted">Last Transaction: Aborted</string>
+    <string name="transaction_last_error">Last Transaction: Error</string>
+
+</resources>
diff --git a/cashier/src/main/res/values/styles.xml b/cashier/src/main/res/values/styles.xml
new file mode 100644
index 0000000..4339684
--- /dev/null
+++ b/cashier/src/main/res/values/styles.xml
@@ -0,0 +1,28 @@
+<resources>
+
+    <style name="AppTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+        <item name="colorPrimary">@color/colorPrimary</item>
+        <item name="colorOnPrimary">@color/design_default_color_background</item>
+        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
+        <item name="colorSecondary">@color/colorAccent</item>
+        <item name="colorOnSecondary">@color/design_default_color_background</item>
+        <item name="colorAccent">@color/colorAccent</item>
+    </style>
+
+    <style name="AppTheme.NoActionBar">
+        <item name="windowActionBar">false</item>
+        <item name="windowNoTitle">true</item>
+    </style>
+
+    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.MaterialComponents.ActionBar" />
+
+    <style name="AppTheme.Toolbar" parent="Widget.MaterialComponents.Toolbar.Primary" />
+
+    <style name="AmountButton" parent="Widget.MaterialComponents.Button">
+        <item name="android:minWidth">48dp</item>
+        <item name="android:layout_marginStart">@dimen/default_margin</item>
+        <item name="android:layout_marginEnd">@dimen/default_margin</item>
+        <item name="android:layout_marginTop">16dp</item>
+    </style>
+
+</resources>
diff --git a/cashier/src/main/res/xml/backup_descriptor.xml b/cashier/src/main/res/xml/backup_descriptor.xml
new file mode 100644
index 0000000..a298494
--- /dev/null
+++ b/cashier/src/main/res/xml/backup_descriptor.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ This file is part of GNU Taler
+  ~ (C) 2020 Taler Systems S.A.
+  ~
+  ~ GNU Taler is free software; you can redistribute it and/or modify it under the
+  ~ terms of the GNU General Public License as published by the Free Software
+  ~ Foundation; either version 3, or (at your option) any later version.
+  ~
+  ~ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+  ~ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  ~ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along with
+  ~ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+  -->
+
+<full-backup-content>
+
+</full-backup-content>