Question

I have BroadcastReceiver when new Message is received will start MessageActivity, but how not to start this Activity if my MainActivity is in front of screen?

By the way, I am trying to not use Singleton Activity.

Answer 1

You will need to keep track of your Activity with OnResume and onPause methods.
So something like this should help you to check if MainActivity is on foreground.

private boolean isForeground;

public void onResume() {
    isForeground = true;
}

public void onPause() {
    isForeground = false;
}