Sending a simple message from Service to Activity

Question

I am trying to find a way to send an integer value from my Service to my MainActivity, yet I can't figure it out with the tutorials on the internet. I am using a Handler to receive my messages which I'm sending from a Thread in my Service.

My code for the Thread in the service:

private class ServiceThread extends Thread {
    @Override
    public void run() {
        super.run();
        try{
            Log.i("Service", "TASK PERFORMED");

            int x = 0;
            for (int i = 0; i < 20; i++){
                x += (random.nextInt(20) + 20);
            }
            theInteger = x/20;
            Message msg = Message.obtain();
            msg.what = MY_RND_INT;
            msg.arg1 = theInteger;
            handler.sendMessage(msg);
        }catch(Exception e){
            e.getMessage();
        }
    }
}

My code for attempting to receive the message:

public Messenger mMessenger = new Messenger(new IncomingHandler());


class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case SimpleService.MY_RND_INT:
                rndInt.setText(msg.arg1);
                break;
            default:
                super.handleMessage(msg);
        }
    }
}

Answer 1

Here's how you do it:

Service side

// Supposing that your value is an integer declared somewhere as: int myInteger;
private void sendMessage() {
  // The string "my-message" will be used to filer the intent
  Intent intent = new Intent("my-message");
  // Adding some data
  intent.putExtra("my-integer", myInteger);
  LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}

Activity side

@Override
public void onResume() {
  super.onResume();
  // This registers messageReceiver to receive messages.
  LocalBroadcastManager.getInstance(this)
                       .registerReceiver(messageReceiver, new IntentFilter("my-message"));
}

// Handling the received Intents for the "my-integer" event 
private BroadcastReceiver messageReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
    // Extract data included in the Intent
    int yourInteger = intent.getIntExtra("my-integer", -1); // -1 is going to be used as the default value
  }
};
    
@Override
protected void onPause() {
  // Unregister since the activity is not visible
  LocalBroadcastManager.getInstance(this).unregisterReceiver(messageReceiver);
  super.onPause();
}