使用Messenger

Messenger可以翻译为“信使”，顾名思义，通过它可以再不同进程间传递数据。Mesenger其实是一种轻量级的IPC，它的底层实现就是AIDL。从构造函数就可以看出来

    public Messenger(Handler target) {        mTarget = target.getIMessenger();    }    public Messenger(IBinder target) {        mTarget = IMessenger.Stub.asInterface(target);    }

使用方法

1.服务端进程

创建一个Service处理连接请求，同时创建一个Handler来创建一个Messenger对象，然后在onBind返回这个Binder

public class MessengerService extends Service {    @Override    public IBinder onBind(Intent intent) {        return mMessenger.getBinder();    }    private static class MessengerHandler extends Handler {        @Override        public void handleMessage(Message msg) {            if (msg.what == 0x001) {                Log.i("server", msg.getData().getString("msg"));                // 回复消息给客户端                Messenger client = msg.replyTo;                Message replayMessage = Message.obtain(null, 0x002);                Bundle bundle = new Bundle();                bundle.putString("reply", "消息收到");                replayMessage.setData(bundle);                try {                    client.send(replayMessage);                } catch (RemoteException e) {                    e.printStackTrace();                }            }        }    }    private Messenger mMessenger = new Messenger(new MessengerHandler());}

2.客户端进程

首先要绑定Service，绑定成功后用返回的IBinder对象创建一个Messenger，通过这个Messenger就可以向服务端发送消息了。如果需要服务端能够回应客户端，我们还需要创建一个Handler并新创建一个Messenger，并把这个Messenger对象通过Message的replyTo函数传给服务端

public class MainActivity extends Activity {    private Messenger mService;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Intent intent = new Intent(this, MessengerService.class);        bindService(intent, connection, Context.BIND_AUTO_CREATE);    }    private ServiceConnection connection = new ServiceConnection() {        @Override        public void onServiceDisconnected(ComponentName name) {        }        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            mService = new Messenger(service);            Message message = Message.obtain(null, 0x001);            Bundle date = new Bundle();            date.putString("msg", "hello, this is client");            message.setData(date);            // 注意            message.replyTo = mGetMessenger;            try {                mService.send(message);            } catch (RemoteException e) {                e.printStackTrace();            }        }    };    protected void onDestroy() {        unbindService(connection);        super.onDestroy();    };    // 下面是客户端接收消息    private Messenger mGetMessenger = new Messenger(new MessengerGetHandler());    private static class MessengerGetHandler extends Handler {        @Override        public void handleMessage(Message msg) {            if (msg.what == 0x002) {                Log.i("client", msg.getData().getString("reply"));            }        }    }}

注册Service

<service android:name=".service.MessengerService"              android:process=":remote"></service>