android跨进程通信之Messenger

    实现客户端向服务端发送一个字符串,服务端回复一个字符串Messenger和Message都实现了parcelable接口,因此可以跨进程传输,简单来说Message所支持的数据类型就是Messenger所支持的传输类型

Messenger的工作原理图

服务端代码

import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.annotation.Nullable;
import android.util.Log;

/**
 * Created by WangPeng on 2018/6/22.
 */
public class MyService extends Service {
    private static final String TAG = "MyService";
    private static class MyHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case MyConstants.CLIENT:
                    Log.i(TAG, "handleMessage: "+msg.getData().getString("msg"));
                    Messenger client = msg.replyTo;
                    Message replyMessage = Message.obtain(null,MyConstants.SERVICE);
                    Bundle args = new Bundle();
                    args.putString("reply","你的消息已经收到,稍后回复你");
                    replyMessage.setData(args);
                    try {
                        client.send(replyMessage);
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                    break;
                    default:
                        super.handleMessage(msg);
            }
            super.handleMessage(msg);
        }
    }
    private final Messenger messenger = new Messenger(new MyHandler());

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return messenger.getBinder();
    }
}

清单文件注册service,并开启一个新进程

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

客户端代码

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    private Messenger messenger;
    private Messenger replyMessenger = new Messenger(new MyReplyHanlder());

    private static class MyReplyHanlder extends Handler {
        private static final String TAG = MainActivity.class.getSimpleName();

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MyConstants.SERVICE:
                    Log.i(TAG, "handleMessage: " + msg.getData().getString("reply"));
                    break;
                default:
                    super.handleMessage(msg);

                    break;
            }
        }
    }

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            messenger = new Messenger(iBinder);
            Message msg = Message.obtain(null, MyConstants.CLIENT);
            Bundle bundle = new Bundle();
            bundle.putString("msg", "hello");
            msg.setData(bundle);
            msg.replyTo = replyMessenger;
            try {
                messenger.send(msg);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent intent = new Intent(this, MyService.class);
        bindService(intent, serviceConnection, BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        unbindService(serviceConnection);
        super.onDestroy();
    }
}

注意:输出结果的时候是在不同的进程中打印

Messenger是以串行的方式处理客户端发来的消息,如果大量的信息发送到服务端,服务端自能一个个处理,大量并发请求使用Messenger就不合适了