Make apps work on API 21+ (except cashier that needs 23+)

36 files changed, 84 insertions, 73 deletions

diff --git a/anastasis-ui/build.gradle b/anastasis-ui/build.gradle
index cbb0077..17e9530 100644
--- a/anastasis-ui/build.gradle
+++ b/anastasis-ui/build.gradle
@@ -24,7 +24,7 @@ android {
     buildToolsVersion "$build_tools_version"
 
     defaultConfig {
-        minSdkVersion 24
+        minSdkVersion 21
         targetSdkVersion 29
         versionCode 1
         versionName "0.1"
diff --git a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/IntroFragment.kt b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/IntroFragment.kt
index 1e5a8d1..d8f0185 100644
--- a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/IntroFragment.kt
+++ b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/IntroFragment.kt
@@ -21,7 +21,6 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
-import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import kotlinx.android.synthetic.main.fragment_intro.*
 
diff --git a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/AuthenticationFragment.kt b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/AuthenticationFragment.kt
index 5f7ab2e..59d0410 100644
--- a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/AuthenticationFragment.kt
+++ b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/AuthenticationFragment.kt
@@ -26,7 +26,6 @@ import android.widget.Toast.LENGTH_SHORT
 import androidx.annotation.IdRes
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
-import androidx.lifecycle.Observer
 import androidx.navigation.fragment.FragmentNavigatorExtras
 import androidx.navigation.fragment.findNavController
 import com.google.android.material.card.MaterialCardView
diff --git a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/SmsFragment.kt b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/SmsFragment.kt
index 2daf14a..a5d872d 100644
--- a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/SmsFragment.kt
+++ b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/authentication/SmsFragment.kt
@@ -26,6 +26,7 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.annotation.RequiresPermission
 import androidx.core.content.ContextCompat
+import androidx.core.content.getSystemService
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
@@ -95,7 +96,7 @@ class SmsFragment : Fragment() {
     @SuppressLint("HardwareIds")
     @RequiresPermission(PERMISSION)
     private fun fillPhoneNumber() {
-        val telephonyService = requireContext().getSystemService(TelephonyManager::class.java)
+        val telephonyService = requireContext().getSystemService<TelephonyManager>()
         telephonyService?.line1Number?.let { phoneNumber ->
             smsView.editText?.setText(phoneNumber)
             smsView.editText?.setSelection(phoneNumber.length)
diff --git a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/identity/IdentityFragment.kt b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/identity/IdentityFragment.kt
index bcfbf24..ad97ab6 100644
--- a/anastasis-ui/src/main/java/org/gnu/anastasis/ui/identity/IdentityFragment.kt
+++ b/anastasis-ui/src/main/java/org/gnu/anastasis/ui/identity/IdentityFragment.kt
@@ -18,15 +18,18 @@ package org.gnu.anastasis.ui.identity
 
 import android.annotation.SuppressLint
 import android.app.DatePickerDialog
+import android.os.Build.VERSION.SDK_INT
 import android.os.Bundle
 import android.telephony.TelephonyManager
 import android.text.format.DateFormat.getDateFormat
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.Toast
+import android.widget.Toast.LENGTH_LONG
+import androidx.core.content.getSystemService
 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_identity.*
 import org.gnu.anastasis.ui.MainViewModel
@@ -63,17 +66,22 @@ class AnastasisIdentityFragment : Fragment() {
             findNavController().navigate(R.id.action_nav_anastasis_identity_to_nav_change_location)
         }
         birthDateInput.editText?.setOnClickListener {
-            val picker = DatePickerDialog(requireContext())
-            picker.datePicker.maxDate = System.currentTimeMillis() - DAYS.toMillis(365) * MIN_AGE
-            picker.setOnDateSetListener { _, year, month, dayOfMonth ->
-                val calender = Calendar.getInstance().apply {
-                    set(year, month, dayOfMonth)
+            if (SDK_INT >= 24) {
+                val picker = DatePickerDialog(requireContext())
+                picker.datePicker.maxDate =
+                    System.currentTimeMillis() - DAYS.toMillis(365) * MIN_AGE
+                picker.setOnDateSetListener { _, year, month, dayOfMonth ->
+                    val calender = Calendar.getInstance().apply {
+                        set(year, month, dayOfMonth)
+                    }
+                    val date = Date(calender.timeInMillis)
+                    val dateStr = getDateFormat(requireContext()).format(date)
+                    birthDateInput.editText?.setText(dateStr)
                 }
-                val date = Date(calender.timeInMillis)
-                val dateStr = getDateFormat(requireContext()).format(date)
-                birthDateInput.editText?.setText(dateStr)
+                picker.show()
+            } else {
+                Toast.makeText(requireContext(), "Needs newer phone", LENGTH_LONG).show()
             }
-            picker.show()
         }
         createIdentifierButton.setOnClickListener {
             findNavController().navigate(R.id.action_nav_anastasis_intro_to_nav_anastasis_authentication)
@@ -82,7 +90,7 @@ class AnastasisIdentityFragment : Fragment() {
 
     @Suppress("unused")
     private fun getCountryName(): String {
-        val tm = requireContext().getSystemService(TelephonyManager::class.java)!!
+        val tm = requireContext().getSystemService<TelephonyManager>()!!
         val countryIso = if (tm.networkCountryIso.isNullOrEmpty()) {
             if (tm.simCountryIso.isNullOrEmpty()) {
                 if (Locale.getDefault().country.isNullOrEmpty()) "unknown"
diff --git a/anastasis-ui/src/main/res/layout/fragment_identity.xml b/anastasis-ui/src/main/res/layout/fragment_identity.xml
index bcf6e4d..4a48d32 100644
--- a/anastasis-ui/src/main/res/layout/fragment_identity.xml
+++ b/anastasis-ui/src/main/res/layout/fragment_identity.xml
@@ -16,6 +16,7 @@
 
 <ScrollView 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"
     android:fillViewport="true">
@@ -31,7 +32,8 @@
             android:layout_margin="16dp"
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toTopOf="parent"
-            app:srcCompat="@drawable/ic_baseline_person" />
+            app:srcCompat="@drawable/ic_baseline_person"
+            tools:ignore="ContentDescription" />
 
         <TextView
             android:id="@+id/identityIntro"
diff --git a/anastasis-ui/src/main/res/layout/fragment_intro.xml b/anastasis-ui/src/main/res/layout/fragment_intro.xml
index 32b5b33..04e5d60 100644
--- a/anastasis-ui/src/main/res/layout/fragment_intro.xml
+++ b/anastasis-ui/src/main/res/layout/fragment_intro.xml
@@ -16,6 +16,7 @@
 
 <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">
 
@@ -33,7 +34,8 @@
         app:layout_constraintVertical_bias="1.0"
         app:layout_constraintVertical_chainStyle="spread"
         app:srcCompat="@drawable/ic_baseline_cloud_circle"
-        app:tint="@color/green" />
+        app:tint="@color/green"
+        tools:ignore="ContentDescription" />
 
     <TextView
         android:id="@+id/textView"
diff --git a/anastasis-ui/src/main/res/layout/fragment_security_question.xml b/anastasis-ui/src/main/res/layout/fragment_security_question.xml
index 4df4f97..5a7c41f 100644
--- a/anastasis-ui/src/main/res/layout/fragment_security_question.xml
+++ b/anastasis-ui/src/main/res/layout/fragment_security_question.xml
@@ -16,6 +16,7 @@
 
 <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">
 
@@ -80,11 +81,12 @@
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
         android:background="?attr/selectableItemBackground"
-        android:drawableTint="?attr/colorOnPrimarySurface"
         android:src="@drawable/ic_add_circle"
         android:text="Save"
+        app:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/questionCard" />
+        app:layout_constraintTop_toBottomOf="@+id/questionCard"
+        tools:ignore="ContentDescription" />
 
     <Button
         android:id="@+id/saveQuestionButton"
@@ -92,8 +94,8 @@
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
         android:backgroundTint="@color/green"
-        android:drawableTint="?attr/colorOnPrimarySurface"
         android:text="Save"
+        app:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent" />
 
diff --git a/anastasis-ui/src/main/res/layout/fragment_sms.xml b/anastasis-ui/src/main/res/layout/fragment_sms.xml
index f855d38..c80f892 100644
--- a/anastasis-ui/src/main/res/layout/fragment_sms.xml
+++ b/anastasis-ui/src/main/res/layout/fragment_sms.xml
@@ -43,8 +43,8 @@
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
         android:backgroundTint="@color/green"
-        android:drawableTint="?attr/colorOnPrimarySurface"
         android:text="Save"
+        app:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent" />
 
diff --git a/anastasis-ui/src/main/res/layout/fragment_video.xml b/anastasis-ui/src/main/res/layout/fragment_video.xml
index c08e269..ecdd102 100644
--- a/anastasis-ui/src/main/res/layout/fragment_video.xml
+++ b/anastasis-ui/src/main/res/layout/fragment_video.xml
@@ -47,12 +47,12 @@
         android:layout_margin="16dp"
         android:scaleType="fitCenter"
         android:visibility="gone"
-        tools:visibility="visible"
         app:layout_constraintBottom_toTopOf="@+id/saveVideoButton"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/videoIntro"
-        tools:srcCompat="@tools:sample/avatars" />
+        tools:srcCompat="@tools:sample/avatars"
+        tools:visibility="visible" />
 
     <Button
         android:id="@+id/takePhotoButton"
@@ -80,9 +80,9 @@
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
         android:backgroundTint="@color/green"
-        android:drawableTint="?attr/colorOnPrimarySurface"
         android:enabled="false"
         android:text="Save"
+        app:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent" />
 
diff --git a/cashier/build.gradle b/cashier/build.gradle
index a749353..337a427 100644
--- a/cashier/build.gradle
+++ b/cashier/build.gradle
@@ -28,7 +28,7 @@ android {
 
     defaultConfig {
         applicationId "net.taler.cashier"
-        minSdkVersion 24
+        minSdkVersion 23
         targetSdkVersion 29
         versionCode 1
         versionName "0.1"
@@ -70,7 +70,7 @@ android {
 dependencies {
     implementation project(":taler-kotlin-android")
     implementation "androidx.constraintlayout:constraintlayout:$constraintlayout_version"
-    implementation 'androidx.security:security-crypto:1.0.0-rc03'
+    implementation 'androidx.security:security-crypto:1.0.0-rc03' // requires minSdk 23
     implementation "com.google.android.material:material:$material_version"
 
     implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
diff --git a/cashier/proguard-rules.pro b/cashier/proguard-rules.pro
index a1cc1f6..ced7b5c 100644
--- a/cashier/proguard-rules.pro
+++ b/cashier/proguard-rules.pro
@@ -20,6 +20,7 @@
 # hide the original source file name.
 #-renamesourcefileattribute SourceFile
 
+#noinspection ShrinkerUnresolvedReference
 -keep class net.taler.cashier.** {*;}
 
 # androidx.security:security-crypto
diff --git a/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt b/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt
index 541bca2..86ace20 100644
--- a/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt
+++ b/cashier/src/main/java/net/taler/cashier/BalanceFragment.kt
@@ -27,7 +27,6 @@ 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 net.taler.cashier.BalanceFragmentDirections.Companion.actionBalanceFragmentToTransactionFragment
 import net.taler.cashier.databinding.FragmentBalanceBinding
diff --git a/cashier/src/main/res/layout-w550dp/fragment_balance.xml b/cashier/src/main/res/layout-w550dp/fragment_balance.xml
index bcfffc7..5023aba 100644
--- a/cashier/src/main/res/layout-w550dp/fragment_balance.xml
+++ b/cashier/src/main/res/layout-w550dp/fragment_balance.xml
@@ -208,9 +208,9 @@
         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:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="@+id/guideline"
diff --git a/cashier/src/main/res/layout/fragment_balance.xml b/cashier/src/main/res/layout/fragment_balance.xml
index 5a11b2a..b8a8012 100644
--- a/cashier/src/main/res/layout/fragment_balance.xml
+++ b/cashier/src/main/res/layout/fragment_balance.xml
@@ -211,9 +211,9 @@
         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:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintHorizontal_bias="0.5"
diff --git a/cashier/src/main/res/values/strings.xml b/cashier/src/main/res/values/strings.xml
index 0400f82..4a8064f 100644
--- a/cashier/src/main/res/values/strings.xml
+++ b/cashier/src/main/res/values/strings.xml
@@ -1,4 +1,4 @@
-<resources xmlns:tools="http://schemas.android.com/tools">
+<resources>
     <string name="app_name">Taler Cashier</string>
 
     <string name="config_bank_url">Bank API address</string>
diff --git a/merchant-terminal/build.gradle b/merchant-terminal/build.gradle
index d56dd5c..1f803cb 100644
--- a/merchant-terminal/build.gradle
+++ b/merchant-terminal/build.gradle
@@ -12,7 +12,7 @@ android {
 
     defaultConfig {
         applicationId "net.taler.merchantpos"
-        minSdkVersion 24
+        minSdkVersion 21
         targetSdkVersion 29
         versionCode 2
         versionName "0.1"
@@ -78,5 +78,5 @@ dependencies {
     implementation "androidx.swiperefreshlayout:swiperefreshlayout:1.1.0"
 
     testImplementation 'androidx.test.ext:junit:1.1.2'
-    testImplementation 'org.robolectric:robolectric:4.3.1'
+    testImplementation 'org.robolectric:robolectric:4.4'
 }
diff --git a/merchant-terminal/proguard-rules.pro b/merchant-terminal/proguard-rules.pro
index 1a50a50..f417733 100644
--- a/merchant-terminal/proguard-rules.pro
+++ b/merchant-terminal/proguard-rules.pro
@@ -20,4 +20,5 @@
 # hide the original source file name.
 #-renamesourcefileattribute SourceFile
 
+#noinspection ShrinkerUnresolvedReference
 -keep class net.taler.merchantpos.** {*;}
diff --git a/merchant-terminal/src/main/java/net/taler/merchantpos/history/HistoryItemAdapter.kt b/merchant-terminal/src/main/java/net/taler/merchantpos/history/HistoryItemAdapter.kt
index 25e94fb..4643cb4 100644
--- a/merchant-terminal/src/main/java/net/taler/merchantpos/history/HistoryItemAdapter.kt
+++ b/merchant-terminal/src/main/java/net/taler/merchantpos/history/HistoryItemAdapter.kt
@@ -21,6 +21,7 @@ import android.view.View
 import android.view.ViewGroup
 import android.widget.ImageButton
 import android.widget.TextView
+import androidx.core.content.ContextCompat.getColor
 import androidx.recyclerview.widget.RecyclerView
 import androidx.recyclerview.widget.RecyclerView.Adapter
 import net.taler.common.toRelativeTime
@@ -73,7 +74,7 @@ internal class HistoryItemAdapter(private val listener: RefundClickListener) :
                 orderIdView.setTextColor(orderIdColor)
             } else {
                 orderIdView.text = v.context.getString(R.string.history_unpaid)
-                orderIdView.setTextColor(v.context.getColor(R.color.red))
+                orderIdView.setTextColor(getColor(v.context, R.color.red))
             }
             if (item.refundable) {
                 refundButton.visibility = View.VISIBLE
diff --git a/merchant-terminal/src/main/java/net/taler/merchantpos/order/Order.kt b/merchant-terminal/src/main/java/net/taler/merchantpos/order/Order.kt
index 4fc2907..0bea20c 100644
--- a/merchant-terminal/src/main/java/net/taler/merchantpos/order/Order.kt
+++ b/merchant-terminal/src/main/java/net/taler/merchantpos/order/Order.kt
@@ -84,7 +84,7 @@ data class Order(val id: Int, val currency: String, val availableCategories: Map
      * Returns a map of i18n summaries for each locale present in *all* given [Category]s
      * or null if there's no locale that fulfills this criteria.
      */
-    val summaryI18n: Map<String, String>?
+    private val summaryI18n: Map<String, String>?
         get() {
             if (products.size == 1) return products[0].descriptionI18n
             val categoryQuantities = getCategoryQuantities()
diff --git a/merchant-terminal/src/main/java/net/taler/merchantpos/refund/RefundFragment.kt b/merchant-terminal/src/main/java/net/taler/merchantpos/refund/RefundFragment.kt
index 5306b2f..bb98dbd 100644
--- a/merchant-terminal/src/main/java/net/taler/merchantpos/refund/RefundFragment.kt
+++ b/merchant-terminal/src/main/java/net/taler/merchantpos/refund/RefundFragment.kt
@@ -24,8 +24,6 @@ import androidx.annotation.StringRes
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
-import com.google.android.material.snackbar.BaseTransientBottomBar.LENGTH_LONG
-import com.google.android.material.snackbar.Snackbar
 import net.taler.common.fadeIn
 import net.taler.common.fadeOut
 import net.taler.common.navigate
diff --git a/taler-kotlin-android/README.md b/taler-kotlin-android/README.md
new file mode 100644
index 0000000..c5273de
--- /dev/null
+++ b/taler-kotlin-android/README.md
@@ -0,0 +1,6 @@
+# GNU Taler Kotlin Library for Android
+
+This library provided basic GNU Taler functionality to Android apps. 
+
+Warning: If you use this library and need bar code scanning, please target at least SDK version 24
+         or set `coreLibraryDesugaringEnabled` to `true` in `android.compileOptions`.
diff --git a/taler-kotlin-android/build.gradle b/taler-kotlin-android/build.gradle
index acd2dc7..d06fde3 100644
--- a/taler-kotlin-android/build.gradle
+++ b/taler-kotlin-android/build.gradle
@@ -27,7 +27,7 @@ android {
     buildToolsVersion "$build_tools_version"
 
     defaultConfig {
-        minSdkVersion 24
+        minSdkVersion 21
         targetSdkVersion 29
         versionCode 1
         versionName "0.1"
@@ -72,7 +72,7 @@ dependencies {
     implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
 
     // QR codes
-    implementation 'com.google.zxing:core:3.4.0'  // needs minSdkVersion 24+
+    implementation 'com.google.zxing:core:3.4.0'  // needs minSdkVersion 24+ or desugar
 
     // Logcat viewer
     implementation('com.github.pedrovgs:lynx:1.1.0') {
diff --git a/taler-kotlin-android/src/main/AndroidManifest.xml b/taler-kotlin-android/src/main/AndroidManifest.xml
index 902ddc1..f74aae6 100644
--- a/taler-kotlin-android/src/main/AndroidManifest.xml
+++ b/taler-kotlin-android/src/main/AndroidManifest.xml
@@ -15,8 +15,11 @@
   -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     package="net.taler.common">
 
+    <uses-sdk tools:overrideLibrary="com.google.zxing.client.android" />
+
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.NFC" />
diff --git a/wallet/build.gradle b/wallet/build.gradle
index b5720be..02123ee 100644
--- a/wallet/build.gradle
+++ b/wallet/build.gradle
@@ -45,7 +45,7 @@ android {
 
     defaultConfig {
         applicationId "net.taler.wallet"
-        minSdkVersion 24
+        minSdkVersion 21
         targetSdkVersion 29
         versionCode 8
         versionName "v0.8.0-rc.3"
@@ -82,6 +82,9 @@ android {
     compileOptions {
         sourceCompatibility = 1.8
         targetCompatibility = 1.8
+
+        // Flag to enable support for the new language APIs for zxing
+        coreLibraryDesugaringEnabled true
     }
 
     kotlinOptions {
@@ -129,6 +132,8 @@ dependencies {
 
     // QR codes
     implementation 'com.journeyapps:zxing-android-embedded:4.0.2@aar'
+    // needed to support zxing library in taler-kotlin-android on API < 24
+    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.0.10'
 
     // Nicer ProgressBar
     implementation 'me.zhanghai.android.materialprogressbar:library:1.6.1'
diff --git a/wallet/fastlane/Fastfile b/wallet/fastlane/Fastfile
index 3c2f8cd..695540c 100644
--- a/wallet/fastlane/Fastfile
+++ b/wallet/fastlane/Fastfile
@@ -42,7 +42,7 @@ platform :android do
         skip_upload_images: 'true',
         skip_upload_screenshots: 'true',
         skip_upload_apk: 'true', # This is an app bundle, so APK is not possible
-        validate_only: 'true'
+        validate_only: 'false'
     )
   end
 end
diff --git a/wallet/proguard-rules.pro b/wallet/proguard-rules.pro
index 27f3799..ca6bc15 100644
--- a/wallet/proguard-rules.pro
+++ b/wallet/proguard-rules.pro
@@ -22,4 +22,5 @@
 
 -keep class akono.AkonoJni {*;}
 
+#noinspection ShrinkerUnresolvedReference
 -keep class net.taler.wallet.** {*;}
diff --git a/wallet/src/main/AndroidManifest.xml b/wallet/src/main/AndroidManifest.xml
index e2a79da..b011583 100644
--- a/wallet/src/main/AndroidManifest.xml
+++ b/wallet/src/main/AndroidManifest.xml
@@ -32,14 +32,15 @@
 
     <application
         android:allowBackup="true"
+        android:extractNativeLibs="true"
         android:fullBackupContent="@xml/backup_descriptor"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme"
-        android:extractNativeLibs="true"
-        tools:ignore="GoogleAppIndexingWarning">
+        tools:ignore="GoogleAppIndexingWarning"
+        tools:targetApi="m">
 
         <activity
             android:name=".MainActivity"
diff --git a/wallet/src/main/java/net/taler/wallet/UriInputFragment.kt b/wallet/src/main/java/net/taler/wallet/UriInputFragment.kt
index d17977b..f4a5f23 100644
--- a/wallet/src/main/java/net/taler/wallet/UriInputFragment.kt
+++ b/wallet/src/main/java/net/taler/wallet/UriInputFragment.kt
@@ -26,6 +26,7 @@ import android.view.View
 import android.view.ViewGroup
 import android.widget.Toast
 import android.widget.Toast.LENGTH_LONG
+import androidx.core.content.getSystemService
 import androidx.fragment.app.Fragment
 import net.taler.wallet.databinding.FragmentUriInputBinding
 
@@ -43,10 +44,10 @@ class UriInputFragment : Fragment() {
     }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
-        val clipboard = requireContext().getSystemService(ClipboardManager::class.java)!!
+        val clipboard = requireContext().getSystemService<ClipboardManager>()
 
         ui.pasteButton.setOnClickListener {
-            val item = clipboard.primaryClip?.getItemAt(0)
+            val item = clipboard?.primaryClip?.getItemAt(0)
             if (item?.text != null) {
                 ui.uriView.setText(item.text)
             } else {
diff --git a/wallet/src/main/java/net/taler/wallet/Utils.kt b/wallet/src/main/java/net/taler/wallet/Utils.kt
index ea01552..388bf61 100644
--- a/wallet/src/main/java/net/taler/wallet/Utils.kt
+++ b/wallet/src/main/java/net/taler/wallet/Utils.kt
@@ -29,8 +29,8 @@ import android.os.Build.VERSION.SDK_INT
 import android.widget.Toast
 import android.widget.Toast.LENGTH_LONG
 import androidx.annotation.RequiresApi
+import androidx.core.content.getSystemService
 import com.google.zxing.integration.android.IntentIntegrator
-import org.json.JSONObject
 
 fun scanQrCode(activity: Activity) {
     IntentIntegrator(activity).apply {
@@ -69,7 +69,7 @@ private fun connectToWifi29(context: Context, ssid: String) {
 
 @Suppress("DEPRECATION")
 private fun connectToWifiDeprecated(context: Context, ssid: String) {
-    context.getSystemService(WifiManager::class.java)?.apply {
+    context.getSystemService<WifiManager>()?.apply {
         if (!isWifiEnabled) {
             val enabledResult = setWifiEnabled(true)
             while (enabledResult && !isWifiEnabled) Thread.sleep(25)
@@ -91,22 +91,6 @@ private fun connectToWifiDeprecated(context: Context, ssid: String) {
     }
 }
 
-fun getErrorString(json: JSONObject): String {
-    return StringBuilder().apply {
-        append(json.getString("talerErrorCode"))
-        append(" ")
-        append(json.getString("message"))
-        json.optJSONObject("details")?.let { details ->
-            details.optJSONObject("errorResponse")?.let { errorResponse ->
-                append("\n\n")
-                append(errorResponse.optString("code"))
-                append(" ")
-                append(errorResponse.optString("hint"))
-            }
-        }
-    }.toString()
-}
-
 fun cleanExchange(exchange: String) = exchange.let {
     if (it.startsWith("https://")) it.substring(8) else it
 }.trimEnd('/')
diff --git a/wallet/src/main/java/net/taler/wallet/transactions/TransactionAdapter.kt b/wallet/src/main/java/net/taler/wallet/transactions/TransactionAdapter.kt
index 936bbbd..5e492f5 100644
--- a/wallet/src/main/java/net/taler/wallet/transactions/TransactionAdapter.kt
+++ b/wallet/src/main/java/net/taler/wallet/transactions/TransactionAdapter.kt
@@ -25,6 +25,7 @@ import android.view.View.VISIBLE
 import android.view.ViewGroup
 import android.widget.ImageView
 import android.widget.TextView
+import androidx.core.content.ContextCompat.getColor
 import androidx.recyclerview.selection.ItemDetailsLookup
 import androidx.recyclerview.selection.ItemKeyProvider
 import androidx.recyclerview.selection.SelectionTracker
@@ -80,13 +81,11 @@ internal class TransactionAdapter(
         private val amount: TextView = v.findViewById(R.id.amount)
         private val pendingView: TextView = v.findViewById(R.id.pendingView)
 
-        private val selectableForeground = v.foreground
         private val amountColor = amount.currentTextColor
-        private val red = context.getColor(R.color.red)
-        private val green = context.getColor(R.color.green)
+        private val red = getColor(context, R.color.red)
+        private val green = getColor(context, R.color.green)
 
         fun bind(transaction: Transaction, selected: Boolean) {
-            v.foreground = selectableForeground
             v.setOnClickListener { listener.onTransactionClicked(transaction) }
             v.isActivated = selected
             if (transaction.error == null) {
diff --git a/wallet/src/main/java/net/taler/wallet/withdraw/ManualWithdrawFragment.kt b/wallet/src/main/java/net/taler/wallet/withdraw/ManualWithdrawFragment.kt
index 4b56dd0..f368c68 100644
--- a/wallet/src/main/java/net/taler/wallet/withdraw/ManualWithdrawFragment.kt
+++ b/wallet/src/main/java/net/taler/wallet/withdraw/ManualWithdrawFragment.kt
@@ -53,7 +53,7 @@ class ManualWithdrawFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         ui.qrCodeButton.setOnClickListener { scanQrCode(requireActivity()) }
         ui.currencyView.text = exchangeItem.currency
-        val paymentOptions = exchangeItem.paytoUris.mapNotNull {paytoUri ->
+        val paymentOptions = exchangeItem.paytoUris.mapNotNull { paytoUri ->
             Uri.parse(paytoUri).authority?.toUpperCase(Locale.getDefault())
         }.joinToString(separator = "\n", prefix = "• ")
         ui.paymentOptionsLabel.text =
diff --git a/wallet/src/main/res/layout/fragment_transaction_withdrawal.xml b/wallet/src/main/res/layout/fragment_transaction_withdrawal.xml
index 5a1e82f..8fe3247 100644
--- a/wallet/src/main/res/layout/fragment_transaction_withdrawal.xml
+++ b/wallet/src/main/res/layout/fragment_transaction_withdrawal.xml
@@ -60,8 +60,8 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:drawableLeft="@drawable/ic_account_balance"
-            android:drawableTint="?attr/colorOnPrimarySurface"
             android:text="@string/withdraw_button_confirm_bank"
+            app:drawableTint="?attr/colorOnPrimarySurface"
             app:layout_constraintBottom_toTopOf="@+id/chosenAmountLabel"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
diff --git a/wallet/src/main/res/layout/fragment_uri_input.xml b/wallet/src/main/res/layout/fragment_uri_input.xml
index 60155e3..1e9934f 100644
--- a/wallet/src/main/res/layout/fragment_uri_input.xml
+++ b/wallet/src/main/res/layout/fragment_uri_input.xml
@@ -51,8 +51,8 @@
         android:layout_marginEnd="16dp"
         android:layout_weight="1"
         android:drawableLeft="@drawable/ic_content_paste"
-        android:drawableTint="?attr/colorOnPrimarySurface"
         android:text="@string/paste"
+        app:drawableTint="?attr/colorOnPrimarySurface"
         app:layout_constraintEnd_toStartOf="@+id/okButton"
         app:layout_constraintHorizontal_chainStyle="spread_inside"
         app:layout_constraintStart_toStartOf="parent"
diff --git a/wallet/src/main/res/layout/list_item_exchange.xml b/wallet/src/main/res/layout/list_item_exchange.xml
index c9d1df4..d81e759 100644
--- a/wallet/src/main/res/layout/list_item_exchange.xml
+++ b/wallet/src/main/res/layout/list_item_exchange.xml
@@ -19,8 +19,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:background="@drawable/selectable_background"
-    android:foreground="?attr/selectableItemBackground"
+    android:background="?attr/selectableItemBackground"
     android:paddingTop="16dp"
     android:paddingBottom="16dp">
 
diff --git a/wallet/src/main/res/layout/list_item_transaction.xml b/wallet/src/main/res/layout/list_item_transaction.xml
index 239e656..ed031c3 100644
--- a/wallet/src/main/res/layout/list_item_transaction.xml
+++ b/wallet/src/main/res/layout/list_item_transaction.xml
@@ -19,8 +19,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:background="@drawable/selectable_background"
-    android:foreground="?attr/selectableItemBackground"
+    android:background="?attr/selectableItemBackground"
     android:paddingStart="16dp"
     android:paddingTop="8dp"
     android:paddingEnd="16dp"