mirror of https://codeberg.org/tom79/Fedilab
Thomas
2 years ago
parent
1ac365befa
commit
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package app.fedilab.android.helper
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/*
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* Copyright 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import android.content.Context
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import android.util.AttributeSet
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import android.view.MotionEvent
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import android.view.View
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import android.view.ViewConfiguration
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import android.widget.FrameLayout
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import androidx.viewpager2.widget.ViewPager2
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import androidx.viewpager2.widget.ViewPager2.ORIENTATION_HORIZONTAL
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import kotlin.math.absoluteValue
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import kotlin.math.sign
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/**
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* Layout to wrap a scrollable component inside a ViewPager2. Provided as a solution to the problem
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* where pages of ViewPager2 have nested scrollable elements that scroll in the same direction as
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* ViewPager2. The scrollable element needs to be the immediate and only child of this host layout.
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*
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* This solution has limitations when using multiple levels of nested scrollable elements
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* (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).
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*/
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class NestedScrollableHost : FrameLayout {
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constructor(context: Context) : super(context)
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constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)
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private var touchSlop = 0
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private var initialX = 0f
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private var initialY = 0f
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private val parentViewPager: ViewPager2?
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get() {
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var v: View? = parent as? View
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while (v != null && v !is ViewPager2) {
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v = v.parent as? View
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}
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return v as? ViewPager2
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}
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private val child: View? get() = if (childCount > 0) getChildAt(0) else null
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init {
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touchSlop = ViewConfiguration.get(context).scaledTouchSlop
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}
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private fun canChildScroll(orientation: Int, delta: Float): Boolean {
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val direction = -delta.sign.toInt()
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return when (orientation) {
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0 -> child?.canScrollHorizontally(direction) ?: false
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1 -> child?.canScrollVertically(direction) ?: false
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else -> throw IllegalArgumentException()
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}
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}
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override fun onInterceptTouchEvent(e: MotionEvent): Boolean {
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handleInterceptTouchEvent(e)
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return super.onInterceptTouchEvent(e)
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}
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private fun handleInterceptTouchEvent(e: MotionEvent) {
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val orientation = parentViewPager?.orientation ?: return
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// Early return if child can't scroll in same direction as parent
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if (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f)) {
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return
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}
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if (e.action == MotionEvent.ACTION_DOWN) {
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initialX = e.x
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initialY = e.y
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parent.requestDisallowInterceptTouchEvent(true)
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} else if (e.action == MotionEvent.ACTION_MOVE) {
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val dx = e.x - initialX
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val dy = e.y - initialY
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val isVpHorizontal = orientation == ORIENTATION_HORIZONTAL
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// assuming ViewPager2 touch-slop is 2x touch-slop of child
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val scaledDx = dx.absoluteValue * if (isVpHorizontal) .5f else 1f
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val scaledDy = dy.absoluteValue * if (isVpHorizontal) 1f else .5f
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if (scaledDx > touchSlop || scaledDy > touchSlop) {
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if (isVpHorizontal == (scaledDy > scaledDx)) {
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// Gesture is perpendicular, allow all parents to intercept
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parent.requestDisallowInterceptTouchEvent(false)
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} else {
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// Gesture is parallel, query child if movement in that direction is possible
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if (canChildScroll(orientation, if (isVpHorizontal) dx else dy)) {
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// Child can scroll, disallow all parents to intercept
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parent.requestDisallowInterceptTouchEvent(true)
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} else {
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// Child cannot scroll, allow all parents to intercept
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parent.requestDisallowInterceptTouchEvent(false)
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}
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}
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}
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}
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}
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}
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@ -0,0 +1,44 @@
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package app.fedilab.android.helper;
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import android.view.View;
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import androidx.viewpager2.widget.ViewPager2;
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public class ZoomOutPageTransformer implements ViewPager2.PageTransformer {
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private static final float MIN_SCALE = 0.85f;
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private static final float MIN_ALPHA = 0.5f;
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public void transformPage(View view, float position) {
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int pageWidth = view.getWidth();
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int pageHeight = view.getHeight();
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if (position < -1) { // [-Infinity,-1)
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// This page is way off-screen to the left.
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view.setAlpha(0f);
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} else if (position <= 1) { // [-1,1]
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// Modify the default slide transition to shrink the page as well
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float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
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float vertMargin = pageHeight * (1 - scaleFactor) / 2;
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float horzMargin = pageWidth * (1 - scaleFactor) / 2;
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if (position < 0) {
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view.setTranslationX(horzMargin - vertMargin / 2);
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} else {
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view.setTranslationX(-horzMargin + vertMargin / 2);
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}
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// Scale the page down (between MIN_SCALE and 1)
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view.setScaleX(scaleFactor);
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view.setScaleY(scaleFactor);
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// Fade the page relative to its size.
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view.setAlpha(MIN_ALPHA +
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(scaleFactor - MIN_SCALE) /
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(1 - MIN_SCALE) * (1 - MIN_ALPHA));
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} else { // (1,+Infinity]
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// This page is way off-screen to the right.
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view.setAlpha(0f);
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}
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}
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}
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