Calling activity class method from Service class

Question

I have seen many posts in SO regarding this but could not get the exact and most easy way to call an activity method from service class. Is broadcast receiver only the option? No easy way out ? I just need to call the following method in Activity class after the media player is prepared in Service class .

Activity class:

    public void updateProgress() {
    // set Progress bar values
    songProgressBar.setProgress(0);
    songProgressBar.setMax(100);
    // Updating progress bar
    updateProgressBar();
}

Service class:

   @Override
public IBinder onBind(Intent intent) {
    Log.d(this.getClass().getName(), "BIND");
    return musicBind;
}

@Override
public boolean onUnbind(Intent intent) {
    return false;
}
    @Override
public void onPrepared(MediaPlayer mp) {
    try {
        mp.start();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    }

           // updateProgress();// Need to call the Activity method here 
  }

Answer 1

Define an interface your Service will use to communicate events:

public interface ServiceCallbacks {
    void doSomething();
} 

Write your Service class. Your Activity will bind to this service, so follow the sample shown here. In addition, we will add a method to set the ServiceCallbacks.

public class MyService extends Service {
    // Binder given to clients
    private final IBinder binder = new LocalBinder();
    // Registered callbacks
    private ServiceCallbacks serviceCallbacks;


    // Class used for the client Binder.
    public class LocalBinder extends Binder {
        MyService getService() {
            // Return this instance of MyService so clients can call public methods
            return MyService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    public void setCallbacks(ServiceCallbacks callbacks) {
        serviceCallbacks = callbacks;
    }
}

Write your Activity class following the same guide, but also make it implement your ServiceCallbacks interface. When you bind/unbind from the Service, you will register/unregister it by calling setCallbacks on the Service.

public class MyActivity extends Activity implements ServiceCallbacks {
    private MyService myService;
    private boolean bound = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(...);
    }

    @Override
    protected void onStart() {
        super.onStart();
        // bind to Service
        Intent intent = new Intent(this, MyService.class);
        bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onStop() {
        super.onStop();
        // Unbind from service
        if (bound) {
            myService.setCallbacks(null); // unregister
            unbindService(serviceConnection);
            bound = false;
        }
    }

    /** Callbacks for service binding, passed to bindService() */
    private ServiceConnection serviceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            // cast the IBinder and get MyService instance
            LocalBinder binder = (LocalBinder) service;
            myService = binder.getService();
            bound = true;
            myService.setCallbacks(MyActivity.this); // register
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            bound = false;
        }
    };

    /* Defined by ServiceCallbacks interface */
    @Override
    public void doSomething() {
        ...
    }
}

Now when your service wants to communicate back to the activity, just call one of the interface methods from earlier. Inside your service:

if (serviceCallbacks != null) { 
    serviceCallbacks.doSomething();
}