title: How can I show my activity(screen) on top of in-calling screen?
body: <p>I'm writing an android application which listens the phone calling events. What I want to do is, if there is a call incomes or outgoes, an activity shows with my customized info. I want to this screen keeps showing during the calling period. However, if a call is coming, the system UI which shows the contact always appears on top of my activity.  I've found some apps already realized this function, but mine can't. :(   Is there any way that I can achieve my goal? Any help will be appreciated. </p>