public class MessengerService extends Service{    /** Command to the service to display a message */    static final int MSG_SAY_HELLO = 1;    /**     * Handler of incoming messages from clients.     */    class IncomingHandler extends Handler    {        @Override        public void handleMessage(Message msg)        {            switch (msg.what)            {                case MSG_SAY_HELLO:                    Toast.makeText(getApplicationContext(), "hello!",                            Toast.LENGTH_SHORT).show();                    break;                default:                    super.handleMessage(msg);            }        }    }    /**     * Target we publish for clients to send messages to IncomingHandler.     */    final Messenger mMessenger = new Messenger(new IncomingHandler());    /**     * When binding to the service, we return an interface to our messenger for     * sending messages to the service.     */    @Override    public IBinder onBind(Intent intent)    {        Toast.makeText(getApplicationContext(), "binding", Toast.LENGTH_SHORT)                .show();        return mMessenger.getBinder();    }}

public class ActivityMessenger extends Activity{    /** Messenger for communicating with the service. */    Messenger mService = null;    /** Flag indicating whether we have called bind on the service. */    boolean mBound;    /**     * Class for interacting with the main interface of the service.     */    private ServiceConnection mConnection = new ServiceConnection()    {        public void onServiceConnected(ComponentName className, IBinder service)        {            // This is called when the connection with the service has been            // established, giving us the object we can use to            // interact with the service. We are communicating with the            // service using a Messenger, so here we get a client-side            // representation of that from the raw IBinder object.            mService = new Messenger(service);            mBound = true;        }        public void onServiceDisconnected(ComponentName className)        {            // This is called when the connection with the service has been            // unexpectedly disconnected -- that is, its process crashed.            mService = null;            mBound = false;        }    };    public void sayHello(View v)    {        if (!mBound)            return;        // Create and send a message to the service, using a supported ‘what‘        // value        Message msg = Message                .obtain(null, MessengerService.MSG_SAY_HELLO, 0, 0);        try        {            mService.send(msg);        }        catch (RemoteException e)        {            e.printStackTrace();        }    }    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);    }    @Override    protected void onStart()    {        super.onStart();        // Bind to the service        bindService(new Intent(this, MessengerService.class), mConnection,                Context.BIND_AUTO_CREATE);    }    @Override    protected void onStop()    {        super.onStop();        // Unbind from the service        if (mBound)        {            unbindService(mConnection);            mBound = false;        }    }}