Bring activity front if it is running or create new one with backpress

Question

Let me explain detailed; I have notification and this notification opens B activity with two cases.

Cases :

1. If app is closed. (not running on background)
2. If app is opened. (on background or front)

Case-1

I click to the notification and it opens the B activity with case-1. When i press back i want to go to the A activity and kill B activity. I dont need B activity anymore. Everything easy from here without using flags. When I'm on B activity and press back two times from here, it goes A activity and then closes the app. My trouble here is, if i open the app from navigation buttons of phone (can't remember the name of this button) app is opening from B activity. That's not what i expected. I want to open A activity. Don't want to see B activity anymore.

Case-2

I click to the notification and it opens the B activity with case-2.When i press back i want to bring A activity to the front, without creating anything new. If i press back on B activity, two times and close the app and then again re-open app from navigation button of phone, want to open app from A activity.

So how can i make this correctly, i tried to use flags (i already read docs) but couldn't get work. What flags should i use when i open the B activity and onBackPress method of B activity to go A activity as i wanted

Answer 1

This should be achievable by adding

android:launchMode="singleTask"

to the A activity in the Manifest, then you can just open A activity from B activity onBackPressed and you will have A only once in the stack.

If it's not working the way you want, you can create an abstract class that extends Activity and handle the stack in a static object, then A & B must extend this new class

Answer 2

try this

 Intent intent = new Intent(context, YourActivity.class);
 intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
 startActivity(intent);