问题
I am trying to get multiple touch events on a system overlay view, but am only receiving the MotionEvent.ACTION_OUTSIDE event.
Is there any possible way of getting multiple touch events on a system overlay?
Any examples or links would be very helpful.
回答1:
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.
This is accomplished by:
- Watch for the
ACTION_OUTSIDEmotion event. - When it occurs, test if it occured within the overlay.
- If it did, switch the
LayoutParamstype toTYPE_SYSTEM_ALERT - Once the interaction with the overlay is complete, switch back to
TYPE_SYSTEM_OVERLAY - Repeat
The one thing to keep in mind is that the ACTION_OUTSIDE motion event is always passed on to the rest of the elements on the screen. So, for example, if the overlay is on top of a button, that button will also receive the motion event and there is no way to stop it.
Also make sure you add the SYSTEM_ALERT_WINDOW permission to the mainifest file.
I've posted the complete solution here:
http://www.jawsware.mobi/code_OverlayView/ (UPDATED)
It includes all the source code and a link to download the entire example project.
Update for Android 4.0 - 1/3/2013
To create an overlay view, when setting up the LayoutParams DON'T set the type to TYPE_SYSTEM_OVERLAY.
Instead set it to TYPE_PHONE.
Use the following flags:
FLAG_NOT_TOUCH_MODAL
FLAG_WATCH_OUTSIDE_TOUCH
FLAG_NOT_TOUCH_MODAL << I found this one to be quite important. Without it, focus is given to the overlay and soft-key (home, menu, etc.) presses are not passed to the activity below.
Also, the previous link (above) has been updated to reflect this update.
回答2:
Starting from Android 4.x, Android team Android team fixed a potential security problem by adding a new function adjustWindowParamsLw() in which it will add FLAG_NOT_FOCUSABLE, FLAG_NOT_TOUCHABLE and remove FLAG_WATCH_OUTSIDE_TOUCH flags for TYPE_SYSTEM_OVERLAY window.
That's TYPE_SYSTEM_OVERLAY window won't receive any touch event on ICS platform.
Updated: 2016/5/4 TYPE_TOAST cannot receive touch events on Android 4.0~4.3. It's the same as TYPE_SYSTEM_OVERLAY. On Android 4.4+, TYPE_TOAST removed from the excluded list, so you can use TYPE_TOAST to receive touch events on Android 4.4+ devices.
来源：https://stackoverflow.com/questions/8073803/android-multi-touch-and-type-system-overlay