Android: catch MotionEvent across activities

Question

I have two activities A and B. I would like to have one touch event MotionEvent.ACTION_DOWN caught in A, while still holding down, launch B, then having the release event MotionEvent.ACTION_UP be caught in B.

In A there is a View v that has an OnTouchListener with the following callback:

@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
        startActivity(new Intent(A.this, B.class));
        break;
    case MotionEvent.ACTION_UP:
        // not called
        break;
    }
    // false doesn't work either
    return true;
}

In B there is an overlapping View v2 (over the original v) with the same kind of OnTouchListener but B's "onTouch" is not getting called when activity starts unless I move my finger (regenerating touch events).

Simply put, I am doing an application that would cause a new activity to appear when holding down on the screen and finish when I release the finger.

Is it not possible to have a MotionEvent.ACTION_DOWNed state transfer from one view to another? Or does the new activity B clear any current "on screen touch listeners" only available to A because it was initiated there?

Thanks for any explanation of how these MotionEvents get dispatched to activities and/or any solution/hack to my problem.

score 1 · Answer 1 · answered Oct 06 '11 at 21:47

   @Override
   public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
        startActivity(new Intent(A.this, B.class));
        break;
    case MotionEvent.ACTION_UP:

          // Obtain MotionEvent object
          long downTime = SystemClock.uptimeMillis();
          long eventTime = SystemClock.uptimeMillis() + 100;
          float x = 0.0f;
          float y = 0.0f;
          // List of meta states found here:               developer.android.com/reference/android/view/KeyEvent.html#getMetaState()
          int metaState = 0;
          MotionEvent motionEvent = MotionEvent.obtain(
             downTime, 
             eventTime, 
             MotionEvent.ACTION_UP, 
             x, 
             y, 
             metaState
            );

            // Dispatch touch event to activity (make B static or get the activity var some other way)

            B.OnTouchEvent(motionEvent);
       break;
    }
    // false doesn't work either
    return true;
}

And in B Activity Override OnTouchEvent (make B implements OnTouchListener) like this:

@Override
public bool OnTouchEvent( MotionEvent e )
{
    return someview.OnTouchEvent( e );
}

And remember , someview must be a view in order to catch the ontouchevent , cause the activitys doesn't really knows what to do with it.

Problem is that the case MotionEvent.ACTION_UP part is not called when I release the finger; if it did wouldn't be too hard to dispatch an event to activity B (like the way you did there). — Eric Chen, Oct 07 '11 at 08:12

Android: catch MotionEvent across activities

1 Answers1