How to have Android Service communicate with Activity

Question

I\'m writing my first Android application and trying to get my head around communication between services and activities. I have a Service that will run in the background an

Answer 1

Binding is another way to communicate

Create a callback

public interface MyCallBack{

   public void getResult(String result);

}

Activity side:

1. Implement the interface in the Activity

2. Provide the implementation for the method

3. Bind the Activity to Service

4. Register and Unregister Callback when the Service gets bound and unbound with Activity.

   public class YourActivity extends AppCompatActivity implements MyCallBack{
   
         private Intent notifyMeIntent;
         private GPSService gpsService;
         private boolean bound = false;
   
         @Override
         public void onCreate(Bundle sis){
   
             // activity code ...
   
             startGPSService();
   
         }
   
         @Override
         public void getResult(String result){
          // show in textView textView.setText(result);
         }
   
         @Override
         protected void onStart()
         {
             super.onStart();
             bindService();
         }
   
         @Override
         protected void onStop() {
             super.onStop();
             unbindService();
         }
   
         private ServiceConnection serviceConnection = new ServiceConnection() {
   
               @Override
               public void onServiceConnected(ComponentName className, IBinder service) {
   
                     GPSService.GPSBinder binder = (GPSService.GPSBinder) service;
                     gpsService= binder.getService();
                     bound = true;
                     gpsService.registerCallBack(YourActivity.this); // register
   
              }
   
              @Override
              public void onServiceDisconnected(ComponentName arg0) {
                     bound = false;
              }
         };
   
         private void bindService() {
   
              bindService(notifyMeIntent, serviceConnection, Context.BIND_AUTO_CREATE);
         }
   
         private void unbindService(){
              if (bound) {
                    gpsService.registerCallBack(null); // unregister            
                    unbindService(serviceConnection);
                    bound = false;
               }
         }
   
         // Call this method somewhere to start Your GPSService
         private void startGPSService(){
              notifyMeIntent = new Intent(this, GPSService.class);
              startService(myIntent );
         }
   
    }
   

Service Side:

1. Initialize callback

2. Invoke the callback method whenever needed

    public class GPSService extends Service{
   
        private MyCallBack myCallback;
        private IBinder serviceBinder = new GPSBinder();
   
        public void registerCallBack(MyCallBack myCallback){
             this.myCallback= myCallback;
        }
   
        public class GPSBinder extends Binder{
   
            public GPSService getService(){
                 return GPSService.this;
            }
       }
   
       @Nullable
       @Override
       public IBinder onBind(Intent intent){
            return serviceBinder;
       }
    }