Android : " How To Send On Call Screen Back "

I am trying to create a application, which is capable of making phone calls to the given number at the scheduled time (someting like reminder). But at the same time once it starts to make the call, my application should take a picture from Camera. So after starting the call activity, after few seconds I want the on call screen activity should go to back ground and my own camera app(A activity with surface) should come to the foreground to take a picture.

I tried the above one in the following way,

1. create a Action calll intent and started the call activity from my Applications Main Activity. 2. After few seconds I started my own camera activity from my App Mail Activity.

But it's not working. Once I start the call, the on call screen only showing in the foreground, that camera Activity is not at all coming to forground. So when I give back button the camera Activity is coming to foreground. I don know the reason. Can anyone tell me what's wrong in this. I think am missing some thing inthis.