Getting all MotionEvents with WindowManager.Layout

问题:

My question refers directly to this question. The answer to that question shows how one can create a ViewGroup, embed it inside a WindowManager, and allow the WindowManager to catch MotionEvents through onTouchEvent(MotionEvent event). WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH is the flag that allows this this ViewGroup to receive MotionEvents. However, according to documentation, this flag

...will not receive the full down/move/up gesture

I want to know if there's a work-around or a way so that I can get all touch events including down, move, and up. A proof of concept is in the app Wave Launcher which uses the same concept but is able to receive more than just a single ACTION_OUTSIDE event.

回答1:

No you can not, and that is very much by design.

Wave Launcher doesn't do this, it has a UI element where you start your touch gesture and then as with standard even dispatching all touch events are delivered to the window of the first down point until the final up.

回答2:

I realize this is an old question, but I've stumbled across it while trying to accomplish something similar. I've also found this, hopefully it is helpful to someone: http://www.section465.com/code_OverlayView/

To create an overlay view, when setting up the LayoutParams you need to set the type to TYPE_SYSTEM_OVERLAY and use the flag FLAG_WATCH_OUTSIDE_TOUCH. This presents a problem because as the Android documentation states: "you will not receive the full down/move/up gesture, only the location of the first down as an ACTION_OUTSIDE." In order to receive the full array of touch events you need to use the TYPE_SYSTEM_ALERT type, but this causes the overlay to take over the screen and stop interaction with other elements. The solution is to use both TYPE_SYSTEM_OVERLAY and TYPE_SYSTEM_ALERT and switch between them by changing the type of the LayoutParams as needed.