android incoming call screen

I would like to add details to the incoming call screen on android. lets say I have a string 'x', so I want 'x' to show up on the incoming call screen under the name of the person who is currentl开发者_开发百科y calling.

I know this is possible because of these apps: CallerId, Vringo

I'm pretty new to this area, so I need to know what is the process to achieve that, for example: get the event of incoming call, go to the incoming call interface and so on.

Thanks!

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I think you have to look at the intent receivers (actually called intent filter => have to be defined in your manifest), there should be one for incoming calls. And then you define your own application, with an activity that is made to receive this kind of intent and with the design you like... if i'm not mistaken, it should be this : ACTION_ANSWER

you can find more doc here and there.

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CallerId seems to show Toast on the Call screen or they maybe use WindowManager addView methods (i think Vringo is working in a such way). The most problem in such case is to know that Call Screen is now on the foreground.