[BottomSheetBehavior] Scrolling within a ViewPager2

[DantheCodingGui]

Description: Full description of issue here

I have a ViewPager2 setup with multiple fragments, in one of them I have a persistent bottom sheet.

I'm having an issue whenever I try and drag the bottom sheet, and the parent viewpager will intercept the gesture, interrupting the bottom sheet drag whenever there is any horizontal movement in the gesture.

bottom.sheet.bug.mp4

Expected behavior:

When dragging the bottom sheet, regardless of direction, ViewPager (or any other parents) can't intercept it. Similar behavior to RecyclerView

Android API version:
29

Material Library version:
Tried both 1.3.0 and 1.4.0-alpha01

[znakeeye]

This might be related: https://issuetracker.google.com/issues/191884668
Sample project included!

Did you find a workaround?

[znakeeye]

Actually, I had some success with a CustomBottomSheetBehavior with this simple override:

@Override
public boolean onTouchEvent(@NonNull @NotNull CoordinatorLayout parent,
    @NonNull @NotNull V child, @NonNull @NotNull MotionEvent event) {

    int action = event.getActionMasked();
    if (action == MotionEvent.ACTION_MOVE && getState() == STATE_DRAGGING) {
        parent.getParent().requestDisallowInterceptTouchEvent(true);
    }

    return super.onTouchEvent(parent, child, event);
}

Perhaps the bug fix is to simply disable all touch interceptions above the CoordinatorLayout?

[UdaraWanasinghe]

ViewPager2 is a wrapper class around RecyclerView. The first child of the ViewPager2 is a RecyclerView. By default, this RecyclerView acts as a nested scrolling child. BottomSheet keeps track of the nested scrolling enabled descendent view in each layout process. So it takes RecyclerView inside ViewPager2 as the nested scrolling child. When this happens (When it detects a nested scrolling child), the bottom sheet doesn't intercept the touch events and sends them to the descendent views. Disable nested scrolling in ViewPager2 RecyclerView to avoid this behavior.

(viewPager2.getChildAt(0) as RecyclerView).isNestedScrollingEnabled = false