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/*
* Copyright 2019 The Android Open Source Project
*
* 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.
*
* Source: https://github.com/android/views-widgets-samples/blob/87e58d1/ViewPager2/app/src/main/java/androidx/viewpager2/integration/testapp/NestedScrollableHost.kt
* And modified for our need
*/
package de.danoeh.antennapod.view;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewTreeObserver;
import android.widget.FrameLayout;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.viewpager2.widget.ViewPager2;
import de.danoeh.antennapod.R;
import static androidx.viewpager2.widget.ViewPager2.ORIENTATION_HORIZONTAL;
import static androidx.viewpager2.widget.ViewPager2.ORIENTATION_VERTICAL;
/**
* Layout to wrap a scrollable component inside a ViewPager2. Provided as a solution to the problem
* where pages of ViewPager2 have nested scrollable elements that scroll in the same direction as
* ViewPager2. The scrollable element needs to be the immediate and only child of this host layout.
*
* This solution has limitations when using multiple levels of nested scrollable elements
* (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).
*/ // KhaledAlharthi/NestedScrollableHost.java
public class NestedScrollableHost extends FrameLayout {
private ViewPager2 parentViewPager;
private int touchSlop = 0;
private float initialX = 0f;
private float initialY = 0f;
private int preferVertical = 1;
private int preferHorizontal = 1;
private int scrollDirection = 0;
public NestedScrollableHost(@NonNull Context context) {
super(context);
init(context);
}
public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context);
setAttributes(context, attrs);
}
public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
setAttributes(context, attrs);
}
public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs,
int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init(context);
setAttributes(context, attrs);
}
private void setAttributes(@NonNull Context context, @Nullable AttributeSet attrs) {
TypedArray a = context.getTheme().obtainStyledAttributes(
attrs,
R.styleable.NestedScrollableHost,
0, 0);
try {
preferHorizontal = a.getInteger(R.styleable.NestedScrollableHost_preferHorizontal, 1);
preferVertical = a.getInteger(R.styleable.NestedScrollableHost_preferVertical, 1);
scrollDirection = a.getInteger(R.styleable.NestedScrollableHost_scrollDirection, 0);
} finally {
a.recycle();
}
}
private void init(Context context) {
touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
View v = (View) getParent();
while (v != null && !(v instanceof ViewPager2) || isntSameDirection(v)) {
v = (View) v.getParent();
}
parentViewPager = (ViewPager2) v;
getViewTreeObserver().removeOnPreDrawListener(this);
return false;
}
});
}
private Boolean isntSameDirection(View v) {
int orientation = 0;
switch (scrollDirection) {
default:
case 0:
return false;
case 1:
orientation = ORIENTATION_VERTICAL;
break;
case 2:
orientation = ORIENTATION_HORIZONTAL;
break;
}
return ((v instanceof ViewPager2) && ((ViewPager2) v).getOrientation() != orientation);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
handleInterceptTouchEvent(ev);
return super.onInterceptTouchEvent(ev);
}
private boolean canChildScroll(int orientation, float delta) {
int direction = (int) -delta;
View child = getChildAt(0);
if (orientation == 0) {
return child.canScrollHorizontally(direction);
} else if (orientation == 1) {
return child.canScrollVertically(direction);
} else {
throw new IllegalArgumentException();
}
}
private void handleInterceptTouchEvent(MotionEvent e) {
if (parentViewPager == null) {
return;
}
int orientation = parentViewPager.getOrientation();
boolean preferedDirection = preferHorizontal + preferVertical > 2;
// Early return if child can't scroll in same direction as parent and theres no prefered scroll direction
if (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f) && !preferedDirection) {
return;
}
if (e.getAction() == MotionEvent.ACTION_DOWN) {
initialX = e.getX();
initialY = e.getY();
getParent().requestDisallowInterceptTouchEvent(true);
} else if (e.getAction() == MotionEvent.ACTION_MOVE) {
float dx = e.getX() - initialX;
float dy = e.getY() - initialY;
boolean isVpHorizontal = orientation == ViewPager2.ORIENTATION_HORIZONTAL;
// assuming ViewPager2 touch-slop is 2x touch-slop of child
float scaledDx = Math.abs(dx) * (isVpHorizontal ? 1f : 0.5f) * preferHorizontal;
float scaledDy = Math.abs(dy) * (isVpHorizontal ? 0.5f : 1f) * preferVertical;
if (scaledDx > touchSlop || scaledDy > touchSlop) {
if (isVpHorizontal == (scaledDy > scaledDx)) {
// Gesture is perpendicular, allow all parents to intercept
getParent().requestDisallowInterceptTouchEvent(preferedDirection);
} else {
// Gesture is parallel, query child if movement in that direction is possible
if (canChildScroll(orientation, isVpHorizontal ? dx : dy)) {
// Child can scroll, disallow all parents to intercept
getParent().requestDisallowInterceptTouchEvent(true);
} else {
// Child cannot scroll, allow all parents to intercept
getParent().requestDisallowInterceptTouchEvent(false);
}
}
}
}
}
}
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