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/*
* Copyright 2015 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ca.allanwang.kau.widgets
import android.app.Activity
import android.content.Context
import android.graphics.Color
import android.util.AttributeSet
import android.view.View
import android.widget.FrameLayout
import ca.allanwang.kau.R
import ca.allanwang.kau.utils.*
/**
* A [FrameLayout] which responds to nested scrolls to create drag-dismissable layouts.
* Applies an elasticity factor to reduce movement as you approach the given dismiss distance.
* Optionally also scales down content during drag.
*/
class ElasticDragDismissFrameLayout @JvmOverloads constructor(
context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0, defStyleRes: Int = 0
) : FrameLayout(context, attrs, defStyleAttr, defStyleRes) {
// configurable attribs
private var dragDismissDistance = Float.MAX_VALUE
private var dragDismissFraction = -1f
private var dragDismissScale = 1f
private var shouldScale = false
private var dragElacticity = 0.8f
// state
private var totalDrag: Float = 0f
private var draggingDown = false
private var draggingUp = false
private var callbacks: MutableList<ElasticDragDismissCallback> = mutableListOf()
init {
if (attrs != null) {
val a = getContext().obtainStyledAttributes(attrs, R.styleable.ElasticDragDismissFrameLayout, 0, 0)
dragDismissDistance = a.getDimensionPixelSize(R.styleable.ElasticDragDismissFrameLayout_dragDismissDistance, Int.MAX_VALUE).toFloat()
dragDismissFraction = a.getFloat(R.styleable.ElasticDragDismissFrameLayout_dragDismissFraction, dragDismissFraction)
dragDismissScale = a.getFloat(R.styleable.ElasticDragDismissFrameLayout_dragDismissScale, dragDismissScale)
shouldScale = dragDismissScale != 1f
dragElacticity = a.getFloat(R.styleable.ElasticDragDismissFrameLayout_dragElasticity, dragElacticity)
a.recycle()
}
}
abstract class ElasticDragDismissCallback {
/**
* Called for each drag event.
* @param elasticOffset Indicating the drag offset with elasticity applied i.e. may
* * exceed 1.
* *
* @param elasticOffsetPixels The elastically scaled drag distance in pixels.
* *
* @param rawOffset Value from [0, 1] indicating the raw drag offset i.e.
* * without elasticity applied. A value of 1 indicates that the
* * dismiss distance has been reached.
* *
* @param rawOffsetPixels The raw distance the user has dragged
*/
internal open fun onDrag(elasticOffset: Float, elasticOffsetPixels: Float,
rawOffset: Float, rawOffsetPixels: Float) {
}
/**
* Called when dragging is released and has exceeded the threshold dismiss distance.
*/
internal open fun onDragDismissed() {}
}
override fun onStartNestedScroll(child: View, target: View, nestedScrollAxes: Int): Boolean {
return nestedScrollAxes and View.SCROLL_AXIS_VERTICAL != 0
}
override fun onNestedPreScroll(target: View, dx: Int, dy: Int, consumed: IntArray) {
// if we're in a drag gesture and the user reverses up the we should take those events
if (draggingDown && dy > 0 || draggingUp && dy < 0) {
dragScale(dy)
consumed[1] = dy
}
}
override fun onNestedScroll(target: View, dxConsumed: Int, dyConsumed: Int,
dxUnconsumed: Int, dyUnconsumed: Int) {
dragScale(dyUnconsumed)
}
override fun onStopNestedScroll(child: View) {
if (Math.abs(totalDrag) >= dragDismissDistance) {
dispatchDismissCallback()
} else { // settle back to natural position
animate()
.translationY(0f)
.scaleX(1f)
.scaleY(1f)
.setDuration(200L)
.setInterpolator(AnimHolder.fastOutSlowInInterpolator(context))
.setListener(null)
.start()
totalDrag = 0f
draggingUp = false
draggingDown = draggingUp
dispatchDragCallback(0f, 0f, 0f, 0f)
}
}
override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
super.onSizeChanged(w, h, oldw, oldh)
if (dragDismissFraction > 0f) {
dragDismissDistance = h * dragDismissFraction
}
}
fun addListener(listener: ElasticDragDismissCallback) {
callbacks.add(listener)
}
fun removeListener(listener: ElasticDragDismissCallback) {
callbacks.remove(listener)
}
private fun dragScale(scroll: Int) {
if (scroll == 0) return
totalDrag += scroll.toFloat()
// track the direction & set the pivot point for scaling
// don't double track i.e. if start dragging down and then reverse, keep tracking as
// dragging down until they reach the 'natural' position
if (scroll < 0 && !draggingUp && !draggingDown) {
draggingDown = true
if (shouldScale) pivotY = height.toFloat()
} else if (scroll > 0 && !draggingDown && !draggingUp) {
draggingUp = true
if (shouldScale) pivotY = 0f
}
// how far have we dragged relative to the distance to perform a dismiss
// (0–1 where 1 = dismiss distance). Decreasing logarithmically as we approach the limit
var dragFraction = Math.log10((1 + Math.abs(totalDrag) / dragDismissDistance).toDouble()).toFloat()
// calculate the desired translation given the drag fraction
var dragTo = dragFraction * dragDismissDistance * dragElacticity
if (draggingUp) {
// as we use the absolute magnitude when calculating the drag fraction, need to
// re-apply the drag direction
dragTo *= -1f
}
translationY = dragTo
if (shouldScale) {
val scale = 1 - (1 - dragDismissScale) * dragFraction
scaleX = scale
scaleY = scale
}
// if we've reversed direction and gone past the settle point then clear the flags to
// allow the list to get the scroll events & reset any transforms
if (draggingDown && totalDrag >= 0 || draggingUp && totalDrag <= 0) {
dragFraction = 0f
dragTo = dragFraction
totalDrag = dragTo
draggingUp = false
draggingDown = draggingUp
translationY = 0f
scaleX = 1f
scaleY = 1f
}
dispatchDragCallback(dragFraction, dragTo,
Math.min(1f, Math.abs(totalDrag) / dragDismissDistance), totalDrag)
}
private fun dispatchDragCallback(elasticOffset: Float, elasticOffsetPixels: Float,
rawOffset: Float, rawOffsetPixels: Float) {
callbacks.forEach {
it.onDrag(elasticOffset, elasticOffsetPixels,
rawOffset, rawOffsetPixels)
}
}
private fun dispatchDismissCallback() {
callbacks.forEach { it.onDragDismissed() }
}
/**
* An [ElasticDragDismissCallback] which fades system chrome (i.e. status bar and
* navigation bar) whilst elastic drags are performed and
* [finishes][Activity.finishAfterTransition] the activity when drag dismissed.
*/
open class SystemChromeFader(private val activity: Activity) : ElasticDragDismissCallback() {
private val statusBarAlpha: Int = Color.alpha(activity.statusBarColor)
private val navBarAlpha: Int = Color.alpha(activity.navigationBarColor)
private val fadeNavBar: Boolean = activity.isNavBarOnBottom
public override fun onDrag(elasticOffset: Float, elasticOffsetPixels: Float,
rawOffset: Float, rawOffsetPixels: Float) {
if (elasticOffsetPixels > 0) {
// dragging downward, fade the status bar in proportion
activity.statusBarColor = activity.statusBarColor.withAlpha(((1f - rawOffset) * statusBarAlpha).toInt())
} else if (elasticOffsetPixels == 0f) {
// reset
activity.statusBarColor = activity.statusBarColor.withAlpha(statusBarAlpha)
activity.navigationBarColor = activity.navigationBarColor.withAlpha(navBarAlpha)
} else if (fadeNavBar) {
// dragging upward, fade the navigation bar in proportion
activity.navigationBarColor = activity.navigationBarColor.withAlpha(((1f - rawOffset) * navBarAlpha).toInt())
}
}
public override fun onDragDismissed() {
activity.finishAfterTransition()
}
}
}
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