SwipeDismissBehavior not triggered in Child of programmatically added Coordinator Layout

Question

I have the following view Hierarchy:

So Let's say I have the following:

I programmatically inflate my MyCoordinatorLayout as a child of the LinearLayout. So somewhere this happens:

linearLayout.addView(myCoordinatorLayout, ..., ...);

Now I have the following code:

public class MyCoordinatorLayout extends CoordinatorLayout{
   public void inflate() {
       LayoutInflater.from(getContext()).inflate(R.layout.merge_header_custom_layout, this, true);
       WebView newWebView = new WebView(getContext());
       addView(newWebView, 0, new ViewGroup.LayoutParams.MATCH_PARENT, MATCH_PARENT);
   }

}

public class MyCustomLayout extends LinearLayout{
     @Override
     public void onAttachedToWindow() {
         Log.v(TAG, "onAttachedToWindow() called, now adding swipe behavior"); //This is called as expected!
         addSwipeBehavior();
     }

     private void addSwipeBehavior() {
        final SwipeDismissBehavior<View> swipe = new SwipeDismissBehavior<View>();
        swipe.setSwipeDirection(SWIPE_DIRECTION_ANY);
        swipe.setListener(new SwipeDismissBehavior.OnDismissListener() {
           @Override
           public void onDismiss(View view) {
              Log.v(TAG, "onDismiss called!");
           }
           @Override
           public void onDragStateChanged(int i) {
               Log.v(TAG, "onDragStateChanged()");
           }
        }
        CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) get LayoutParams();
        params.setBehavior(swipe);
        Log.v(TAG, "behavior=" + params.getBehavior); //This shows its set.
     }
}

Here is the problem. The swipe to dismiss does not work at all. In fact, those log statements I added are never printed out. Is it probably because my CoordinatorLayout was added programmatically, not existing in the XML beforehand like the examples I have seen?

I would really like my behavior to work, but it is just not being triggered. Also, I checked the MyCustomLayout and saw that its onTouchEvent(MotionEvent e) is triggered.... However, the behavior is still never triggered. I also did a getLayoutParams() and getBehavior() and it returns the correct behavior so I know the CoordinatorLayout has the correct Behavior, but the behavior isn't just working at all... Not sure if I missed something! Would be great to get some help or point me in the right direction!

Answer 1

I think the first issue is that the SwipeDismissBehavior needs to be associated with a swippable view and the behavior associated of how you want to swipe to dismiss, eg, side to side behavior.setSwipeDirection(SwipeDismissBehavior.SWIPE_DIRECTION_START_TO_END); and then propagate the touch appropriately, or if in a RecyclerView use something like an ItemTouchHelper.

This SO post does a much better job of explaining how to properly set up the swipe to dismiss: How to use SwipeDismissBehavior.OnDismissListener on RecyclerView

Hope this helps.

Answer 2

I was able to figure out why my touch interaction with the SwipeDismissBehavior was never called. The reason was quite simple. In my diagram, I forgot that at the top of the view hierarchy, and on top of the linear layout was a View Pager. Let me redraw the diagram.

What was actually happening was that the ViewPager was intercepting my touch and never letting it reach the child layouts. There was a fix. What I needed to do was the following:

public class MySwipeDismissBehavior extends SwipeDismissBehavior<View> {
     private float mLastX; 

     @Override
     public boolean onInterceptTouchEvent(CoordinatorLayout parent, FrameLayout child, MotionEvent event) {
         if (parent.isPountInChildBounds(child, event.getX(), event.getY())) {
             ViewPager vp = findViewPager(child);
             switch(event.getActionMasked()) {
                 case MotionEvent.ACTION_DOWN:
                     disableViewPager(vp, true);
                     break;
                 case MotionEvent.ACTION_MOVE:
                     boolean swipingLeftToRight = (x-mLastX) > 0; //Allow the view pager to handle it if I swiping from left to right.
                     if (swipingLeftToRight) {
                         disableViewPager(vp, false);
                     } else { // if swiping from right to left, let the swipe dismiss behavior handle it.
                         disableViewPager(vp, true);
                     }
                     break;
                 case MotionEvent.ACTION_UP:
                 case MotionEvent.ACTION_CANCEL: //As soon as it 
                     disableViewPager(vp, true);
                     break;

             }
         }

     }

     private void disableViewPager(ViewPager vp, boolean enable) {
         if (vp != null) {
            vp.requestDisallowInterceptTouchEvent(enable)
         }
     }

     private ViewPager findViewPager(View child) {
          ViewPager parent = child.getParent();
          while (parent != null) {
               parent = child.getParent();
               if (parent instanceof ViewPager) {
                   return (ViewPager) parent;
               } else if(!(parent instanceof View)) {
                   return null;
               } else {
                   child = (View) parent;
               }

          }
          return null;

     }
}

After I added this new behavior to my code, my swipe dismiss behavior works. I hope this is helpful to others. I got help and inspiration for my solution from here: Snack bar dismiss not working. It wasn't exactly the same problem, but it pointed me towards the right direction