How to show popup dialog over lock screen like Android Alarm Clock when getting GCM

I need to show message on top of the lock screen, like Android Alarm Clock is displaying full screen of the alarm, when it's the time to wake up.

Here is a photo of one of the screen popup when there is alarm:

Screenshot

Solution

Window window = getWindow();

window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
        | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
        | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
        | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);