Java – Android puts ongoing calls first?

I’m building a universal access app where my app can use a custom dialer full screen. So if a user presses the home or back key during a call, I need to give them a chance to call back somehow. (In fact, I’m thinking about automatically reopening ongoing calls when they’re away).

I know how to start a call using a number,

but I don’t know how to turn on the call screen during a call, I tried to do Intent.ACTION_CALL without a number, but it will be in the other:

    Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse("tel:"));
    startActivity(callIntent);

I think this should be purposeful, or just put it up front. But I don’t know how to do it. How do I programmatically reopen an ongoing call?

If it’s still relevant or interested in others about it:

ACTION_CALL_BUTTON does exactly that.

If the call is in progress, it will bring it to the front, if not, it will
Bring your call history.

http://developer.android.com/reference/android/content/Intent.html#ACTION_CALL_BUTTON