87 lines
2.8 KiB
Java
87 lines
2.8 KiB
Java
package com.google.android.material.appbar;
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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.widget.OverScroller;
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import androidx.annotation.Nullable;
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import androidx.coordinatorlayout.widget.CoordinatorLayout;
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import java.lang.reflect.Field;
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// See https://stackoverflow.com/questions/56849221#57997489
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public final class FlingBehavior extends AppBarLayout.Behavior {
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public FlingBehavior(final Context context, final AttributeSet attrs) {
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super(context, attrs);
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}
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@Override
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public boolean onInterceptTouchEvent(final CoordinatorLayout parent, final AppBarLayout child,
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final MotionEvent ev) {
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switch (ev.getActionMasked()) {
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case MotionEvent.ACTION_DOWN:
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// remove reference to old nested scrolling child
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resetNestedScrollingChild();
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// Stop fling when your finger touches the screen
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stopAppBarLayoutFling();
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break;
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default:
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break;
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}
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return super.onInterceptTouchEvent(parent, child, ev);
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}
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@Nullable
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private OverScroller getScrollerField() {
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try {
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Class<?> headerBehaviorType = this.getClass()
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.getSuperclass().getSuperclass().getSuperclass();
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if (headerBehaviorType != null) {
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Field field = headerBehaviorType.getDeclaredField("scroller");
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field.setAccessible(true);
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return ((OverScroller) field.get(this));
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}
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} catch (NoSuchFieldException | IllegalAccessException e) {
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// ?
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}
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return null;
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}
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@Nullable
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private Field getLastNestedScrollingChildRefField() {
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try {
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Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass();
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if (headerBehaviorType != null) {
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Field field = headerBehaviorType.getDeclaredField("lastNestedScrollingChildRef");
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field.setAccessible(true);
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return field;
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}
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} catch (NoSuchFieldException e) {
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// ?
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}
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return null;
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}
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private void resetNestedScrollingChild() {
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Field field = getLastNestedScrollingChildRefField();
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if (field != null) {
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try {
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Object value = field.get(this);
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if (value != null) {
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field.set(this, null);
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}
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} catch (IllegalAccessException e) {
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// ?
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}
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}
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}
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private void stopAppBarLayoutFling() {
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OverScroller scroller = getScrollerField();
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if (scroller != null) {
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scroller.forceFinished(true);
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}
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}
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}
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