Pass information to a paused activity to call a method (Not UI update)

Question

Scenerio:

Activity A opens Activity B. Activity B has some filters based on which the content of Activity A will change. To reduce waiting time for the users, I want to notify Activity A to start fetching the content as soon as there is a change on Activity B.

What would be the best way to achieve this without changing activity's structure ?

Answer 1

Ended up using a LocalBroadcastManager. Register a LocalBroadCastManager in Activity A and send a message from Activity B. Unregister it upon exiting Activity A.

In Activity A:

LocalBroadcastManager.getInstance(this).registerReceiver(
  mMessageReceiver, new IntentFilter("CUSTOM-EVENT_NAME"));

private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
      // process the message here
      String data = intent.getStringExtra("intent-key")
    }
};

In Activity B:

Intent intent = new Intent("CUSTOM-EVENT_NAME");
intent.putExtra("intent-key","data");
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);