When would ACTION_OUTSIDE be triggered?

I don't understand when ACTION_OUTSIDE is triggered. Please give me an example.

The doc's g开发者_如何学Goive this cryptic description:

Constant for getAction(): A movement has happened outside of the normal bounds of the UI element. This does not provide a full gesture, but only the initial location of the movement/touch.

http://developer.android.com/reference/android/view/MotionEvent.html#ACTION_OUTSIDE

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I believe it is only used for clicking outside of the current activity (for example a dialog). Check out WindowManager.LayoutParams