android - Updating UI from a service (using a handler?)

Question

I am trying to update my UI in FirstActivity when I receive a notification but is confused by runOnUiThread , Runnable and Handler. Here is what I have: I am running FirstActivity and NotificationService. When NotificationService reeives a notification, it will update FirstActivity UI.

I also have another service AlarmService running. First Activity

@Override
public void onResume() {
      super.onResume();
      //some other code for alarm service
}

NotificationService

    //on receiving notification
    private void showNotification(String text) {

   //Get activity
   Class<?> activityClass = null;
     try {
         activityClass = Class.forName("com.pakage.FirstActivity");
         contextActivity = (Activity) activityClass.newInstance();

         //Update UI on FirstActivity not working
         contextActivity.runOnUiThread(new Runnable() {
             public void run()
             { 
               Looper.prepare();
               TextView tv = (TextView ) contextActivity.findViewById(R.id.notifyTest);
               Looper.loop();

             }
             });

     } catch (Exception e) {
         e.printStackTrace();
     }

            //Shows the notification
            Notification n = new Notification();    
            //... etc   
}

I keep getting looper.prepare error. Do I need to put extra codes in my FirstActivity?

Answer 1

My 1st instinct is that you should instead have the Activity bind to your service and handle the UI update on its side instead of the Service directly modifying the Activity.

See more info here:
http://developer.android.com/reference/android/app/Service.html#LocalServiceSample

And an example here:
Example: Communication between Activity and Service using Messaging