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Android Threads and Services But Wait There's More! Messengers and Handlers: Activity

threads and services

Challenge Task 1 of 4

The goal is to call 'setCoordinates(int lat, int long)' inside MainActivity using the coordinates provided by GeolocationService. This is broken down into four steps, but if you'd like to try it all at once without hints, switch to 'Difficulty.java' and set HARDMODE to true. Otherwise, the first step is to populate mServiceMessenger in MainActivity.

// some methods omitted
public class MainActivity extends Activity {
    Boolean isBound = false;
    Messenger mServiceMessenger;

    ServiceConnection mServiceConnection = new ServiceConnection() {
      public void onServiceConnected(ComponentName name, IBinder binder) {
        isBound = true;

      public void onServiceDisconnected(ComponentName name) {
        isBound = false;
// some methods omitted
public class GeolocationService extends Service {
    int mLatitude;
    int mLongitude;
    Messenger mMessenger = new Messenger(new LocationHandler());

    public IBinder onBind(Intent intent) {
      return mMessenger.getBinder();

   class LocationHandler extends Handler {
      public void handleMessage(Message msg) {
        mLatitude = getLatitude();
        mLongitude = getLongitude();
  public class Difficulty {
    public static Boolean HARDMODE = false;    

1 Answer

mServiceMessenger = new Messenger(binder); hope it works