unable to find the issue

public class TwitterService extends Service {
  TwitterService mService;
  TwitterClient twitterClient = new TwitterClient();    
  TwitterHandler twitterhandle;
  public void onCreate(){
    TwitterThread twitter = new TwitterThread();
    twitter.setName("TwitterThread");
    twitter.start();
    while(twitter.twitterHandler==null){}
    twitterhandle = twitter.twitterHandler;
    twitterhandle.setSevice(this);
  }
  public IBinder onBind(Intent intent) {
        return null;
    }
  public int onStartCommand(Intent intent, int flags, int startId) {
    Message message = Message.obtain();
    message.arg1 = startId;
    twitterhandle.sendMessage(message);
    return Service.START_REDELIVER_INTENT;
  }


  class TwitterThread extends Thread {
    TwitterHandler twitterHandler;
    @Override
    public void run() {
      Looper.prepare();
      twitterHandler = new TwitterHandler();
      Looper.loop();
    }
  }    

  class TwitterHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
      twitterClient.update();
      mService.stopSelf(msg.arg1);
    }
    public void setService(TwitterService service){
      mService = service;
    }
  }
}

public class MainActivity extends Activity {
  Button button;   

  @Override
  public void onCreate(Bundle savedInstanceState) {
    setContentView(R.layout.activity_main);

    button = (Button) findViewById(R.id.update_button);
    button.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v){
            Intent intent = new Intent(MainActivity.this,TwitterService.class);
        startService(intent);
      }
    });
  }
}