使用服务时ClassCastException

我定义了一个本地服务:

public class ComService extends Service implements IComService {
    private IBinder binder = new ComServiceBinder();

    public class ComServiceBinder extends Binder implements IComService.IServiceBinder {
        public IComService getService() {
            return ComService.this;
        }
    }

    public void test(String msg) {
        System.out.println(msg);
    }

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

对应接口:

public interface IComService {
    public void test(String msg);

    public interface IServiceBinder {
        IComService getService();
    }
}

然后我尝试将服务绑定到另一个应用程序中的另一个活动中,在该活动中可以使用相同的接口:

bindService(new Intent("ch.ifi.csg.games4blue.gamebase.api.ComService"), conn, Context.BIND_AUTO_CREATE);

和

private ServiceConnection conn = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        Log.i("INFO", "Service bound " + name);
        comService = ((IComService.IServiceBinder)service).getService();
        serviceHandler.sendEmptyMessage(0);
    }

    @Override
    public void onServiceDisconnected(ComponentName arg0) {
        Log.i("INFO", "Service Unbound ");
    }
};

但是这条线

comService = ((IComService.IServiceBinder)service).getService();

总是抛出一个

05-02 22:12:55.922: ERROR/AndroidRuntime(622): java.lang.ClassCastException: android.os.BinderProxy

我无法解释为什么,我在上跟踪了应用程序示例 http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/app/LocalServiceBinding.html

任何提示都会很好!