Refreshing activity on receiving gcm push notification

Question

Update: GCM is deprecated, use FCM

How to refresh activity on receiving gcm push notification if my app is open. I have an activity which contains listview filled with data from the server. I want to refresh my activity (here adding one more item to listview) , if I receive gcm push notification(which also contains some data).

• One alternative is to add timer that periodically do server requests and update the list adapter data but I don't want these because it will take much resources.
• Do I need to add broadcast receiver which will trigger on receiving gcm push which further request for newer server data and update my activity UI?

Dear commentors, please read the question carefully, I only need to refresh the list (if app is open and that particular activity is open) else no need for same.

Answer 1

Took me a few hours to figure it out. Posting here in case anyone anyone else has the same problem.

The idea is that you have to register your activity as a broadcast receiver. The easiest way to do this is like so:

//register your activity onResume()
@Override
public void onResume() {
    super.onResume();
    context.registerReceiver(mMessageReceiver, new IntentFilter("unique_name"));
}

//Must unregister onPause()
@Override
protected void onPause() {
    super.onPause();
    context.unregisterReceiver(mMessageReceiver);
}


//This is the handler that will manager to process the broadcast intent
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {

        // Extract data included in the Intent
        String message = intent.getStringExtra("message");

        //do other stuff here
    }
};

The above code goes in the activity that you want to 'listen' for events.

Now, how do we send data to this 'listener'? Go to your push notification handler(or from where you want to update your activity) and when you receive a notification call this function:

// This function will create an intent. This intent must take as parameter the "unique_name" that you registered your activity with
static void updateMyActivity(Context context, String message) {

    Intent intent = new Intent("unique_name");

    //put whatever data you want to send, if any
    intent.putExtra("message", message);

    //send broadcast
    context.sendBroadcast(intent);
}

When you call the above function, your activity should receive it.

Note: Your activity must be running/open to receive the broadcast intent

Note2: I switched to a library called 'otto'. It does actually the same thing but easier, 'broadcasts events' thoughout the app. Here's a link http://square.github.io/otto/