Android: Detect if user touches and drags out of button region?

The answer posted by Entreco needed some slight tweaking in my case. I had to substitute:

if(!rect.contains((int)event.getX(), (int)event.getY()))

for

if(!rect.contains(v.getLeft() + (int) event.getX(), v.getTop() + (int) event.getY()))

because event.getX() and event.getY() only apply to the ImageView itself, not the entire screen.

Check the MotionEvent.MOVE_OUTSIDE: Check the MotionEvent.MOVE:

private Rect rect;    // Variable rect to hold the bounds of the view

public boolean onTouch(View v, MotionEvent event) {
    if(event.getAction() == MotionEvent.ACTION_DOWN){
        // Construct a rect of the view's bounds
        rect = new Rect(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());

    }
    if(event.getAction() == MotionEvent.ACTION_MOVE){
        if(!rect.contains(v.getLeft() + (int) event.getX(), v.getTop() + (int) event.getY())){
            // User moved outside bounds
        }
    }
    return false;
}

NOTE: If you want to target Android 4.0, a whole world of new possibilities opens: http://developer.android.com/reference/android/view/MotionEvent.html#ACTION_HOVER_ENTER