自支持lib26.0.0以来出现的崩溃工具栏反弹故障

Question

自从Android支持库从版本25.4.0更新到26.0.0(最高27.0.0)以来，我在活动中的折叠工具栏中遇到了一些奇怪的行为。

查看这些gif的差异：

• 25.4.0
• 26.0.0(+)

当向上滚动时，您将看到折叠工具栏的奇怪反弹。

见以下布局代码片段：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="@+id/appBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/white_opacity10"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsing"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap"
app:scrimAnimationDuration="@integer/scrim_animation_short"
app:titleEnabled="false">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
app:layout_collapseMode="parallax">
<!-- Here is layout of header -->
</FrameLayout>
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_gravity="top"
android:layout_marginBottom="?attr/actionBarSize"
app:layout_collapseMode="pin"/>
<android.support.design.widget.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_gravity="bottom"
app:tabGravity="center"
app:tabMode="scrollable"
app:tabSelectedTextColor="@color/white"
app:tabTextColor="@color/white_inactive"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<FrameLayout
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</FrameLayout>
</android.support.design.widget.CoordinatorLayout>

有人遇到同样的问题吗？这是支持库错误，还是我做错了什么？

编辑：

• 故障只发生在你扔屏幕的时候，而不是拖动的时候
• 为了测试，您可以拉动以下项目：https://github.com/aaronbond/CollapsingToolbarLayoutExample并将支持libs增加到26或更高

Answer 1

我经历了类似的事情，并通过为AppBarLayout定义自定义行为来解决它。

<android.support.design.widget.AppBarLayout
android:id="@+id/main_appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/white_40"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" 
app:layout_behavior="CustomFlingBehavior">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/main_collapsing"
android:layout_width="match_parent"
android:layout_height="144dp"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<LinearLayout
android:id="@+id/ll_horizontal_ruler"
android:layout_width="match_parent"
android:layout_height="1dp"
android:layout_gravity="bottom"
android:orientation="horizontal"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>

和

public final class FlingBehavior extends AppBarLayout.Behavior {
private static final int TOP_CHILD_FLING_THRESHOLD = 3;
private boolean isPositive;
private boolean enabled = true;
public FlingBehavior() {
setDragCallback();
}
public FlingBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
setDragCallback();
}
private void setDragCallback() {
setDragCallback(new DragCallback() {
@Override
public boolean canDrag(@NonNull AppBarLayout appBarLayout) {
return enabled;
}
});
}
@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, 
AppBarLayout child, View target, float 
velocityX, float velocityY, boolean 
consumed) {
if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
velocityY = velocityY * -1;
}
if (target instanceof RecyclerView && velocityY < 0) {
final RecyclerView recyclerView = (RecyclerView) target;
final View firstChild = recyclerView.getChildAt(0);
final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
}
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}
@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
isPositive = dy > 0;
}
public void setEnabled(boolean enabled) {
this.enabled = enabled;
}
@Override
public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes) {
return enabled && super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
}
public boolean isEnabled() {
return enabled;
}
}

其基于这里的答案：https://stackoverflow.com/a/40091360/494179