how does a service return result to an activity

Question

I seem to have a classic task, yet I can't find any examples on how to do it.

I want to download something. Well I call a web service and get a response... but it's pretty much the same.

In order to do this I have an activity that starts a service that spawns a thread that does the job.

Now i would like to use the data I got in the activity that started the service.

(I assume that starting another activity to handle the job of displaying the result would be simple)

My problem is how does the service notify an activity (the one that started it or another one) of something?

Any pointers to examples are much appreciated.

Regards

Answer 1

According to Google documentation, if your Activity and Service are within the same app, using a LocalBroadcastManager is preferable over sendBroadcast (intent) because the information sent does not go through the system which eliminates the risk of interception.

It's quite easy to use.

In your activity, create a BroadcastReceiver and dynamically add a listener in the onResume() method :

private BroadcastReceiver  bReceiver = new BroadcastReceiver(){      @Override     public void onReceive(Context context, Intent intent) {         //put here whaterver you want your activity to do with the intent received     }            };  protected void onResume(){     super.onResume();     LocalBroadcastManager.getInstance(this).registerReceiver(bReceiver, new IntentFilter("message")); }  protected void onPause (){     super.onPause();  LocalBroadcastManager.getInstance(this).unregisterReceiver(bReceiver); } 

And in your service, you get an instance of LocalBroadcastManager and use it to send an intent. I usually put it in its own method like this :

private void sendBroadcast (boolean success){     Intent intent = new Intent ("message"); //put the same message as in the filter you used in the activity when registering the receiver     intent.putExtra("success", success);     LocalBroadcastManager.getInstance(this).sendBroadcast(intent); }