How to detect draglike behavior without ACTION_DOWN and ACTION_UP

Question

My problem concerns onTouch. As far as I can tell, there is no way to detect an ACTION_DOWN for one view, and than detect the ACTION_UP for another view at the same onTouch event or swipe, as every onTouch event is linked to one view.

I have a view (A) with some graphics, and on EVENT_DOWN the coordinates are detected and make a "popup" that consists of a view (B) that ownes some more views ("buttons"). B's position and size may vary form time to time. I would prefer to detect ACTION_UP on one of B's children (the "buttons").

I guess using onInterceptTouchEvent is no good. After all, B is not A's parent. Its the other way around.

Using androids drag-and-drop functionality seems a bit too much. Looks like it's intended for actually dragging graphics and transfering data. Dragging invisible graphics around to detect the finger leaving the screen is not very elegant.

Another way would be detecting B's children's positions (and size), every time the popup is shown, but that is not very smooth either.

What is the best way to detect a view A's ACTION_DOWN, and then its child B's (or it's childrens) ACTION_UP?

Or are there other ways to detect these events?

Answer 1

I did struggle with something very similar for a day or two, and I finally concluded that as far as I know onInterceptTouchEvent is the only way to go. I just created a container view 'C' for A and B, and then when A received an ACTION_DOWN, I instructed 'C' to intercept all further events in the swipe, test the coordinates against B's known location, and then forward the event to 'B' through a custom method if the ACTION_UP tested positive against B's bounds (be careful manually passing MotionEvents from one class to another, as the coordinates will be all wrong).

Not a very satisfying solution, but it was the only thing I could think of to do.

Also just in case you're using it, android 3.0+ has some drag/drop helper methods which I'm sure are very helpful, though I was developing for 2.x so they were useless to me.