Android学习笔记之service通信（Messenger）

Android学习笔记之service通信（Messenger）

1、activity通过bindService方法建立与service的连接，然后使用sMessenger向ServerObserverService发送message

2、ServerObserverService继承 service

private MyHandler cMeeeengerHandler = new MyHandler();
private Messenger sMessenger = new Messenger( cMeeeengerHandler);)

3、重写service里的onBind方法，service里的sMessenger得到IBinder。在与之绑定的activity的onServiceConnected方法里使用这个IBinder来实例化activity里的sMessenger。使用此sMessenger向service发送message。(message通过replyto指定了回应的Messenger 即cMessenger)

4、这时serive的sMessenger即有了message信息，又sMessenger是通过重写了handleMessage的Handler来建立的。故handleMessage可以对message进行处理。

5、service通过handler里的handleMessage处理得到的message，

(这个message告诉了回应的Messenger赋值给cMessenger)

产生回应的Message m，通过cMessenger发送给activity。

//service和activity里都是通过handlerMessage来对收到的消息进行处理，以上activity也可以理解为client

//这个逻辑是真的搞人，我也不知道我这样理解的对不对，目前感觉没问题，欢迎指正

Service

package es.source.code.service;

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Binder;
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.util.Log;

public class ServerObserverService extends Service {
    private static final String Tag = "ServerObserverService";
    public Messenger cMessenger;
    private MyHandler cMeeeengerHandler = new MyHandler();
    public Messenger sMessenger = new Messenger( cMeeeengerHandler);
    private class MyHandler extends Handler{
        @Override
        public void handleMessage(Message msg){
            super.handleMessage(msg);
            switch(msg.what){
                case 1:
                    //开始更新
                    System.out.println("Msg_Food_Get_Start");
                    System.out.println("service:获取客户端message 1 成功");
                    try {
                        for(int i = 3; i > 0; i--) {
                            Thread.sleep(300);
                            Message m = getFoodInfo();
                            System.out.println(m.what);
                            System.out.println(m.getData().get("name"));
                            System.out.println(m.getData().get("storage"));
                            cMessenger = msg.replyTo;
                            try {
                                cMessenger.send(m);
                                System.out.println("发送菜品信息成功");
                            } catch (RemoteException e) {
                                e.printStackTrace();
                            }
                        }
                    }catch(InterruptedException e){
                        e.printStackTrace();
                    }
                    break;

                case 0:
                    Thread.interrupted();
                    System.out.println("Msg_Food_Get_Stop");
                    System.out.println("service:获取客户端message 0 成功");
                    //停止更新
                    break;
                default:

            }
        }
    }
    
    @Override
    public IBinder onBind(Intent intent){
        Log.w("TAG", "Service is binded");
        return sMessenger.getBinder();
    }

    public Message getFoodInfo(){
        Message m =  Message.obtain();
        Bundle bundle = new Bundle();
        bundle.putString("name", "new food");
        int storage = (int)(Math.random()*20);
        bundle.putInt("storage", storage);
        m.setData(bundle);
        m.what = 10;
        return m;
    }

acticity

Messenger cMessenger = new Messenger(new MyHandler());
Messenger sMessenger;
private class MyHandler extends Handler{
@Override
    //对得到的消息进行处理
    public void handleMessage(final Message msg){
        if(msg.what == 10){
            System.out.println("fv:收到服务器发来的消息");
            String name = (String)msg.getData().get("name");
            int storage = (int)msg.getData().get("storage");
            Intent toUpdate = new Intent(FoodView.this, UpdateService.class);
            toUpdate.putExtra("new food", msg.getData());
            startService(toUpdate);
        }
    }
};
private ServiceConnection mConnection = new ServiceConnection() {
    @Override
    //这里就得到service得到的IBinder。所以通过它得到sMessenger，可以通过此sMessenger
    //向service发送消息
    //因为下面有指出message的replyto为cMessenger，而cMessenger通过handler创建，所以可用handler的方法定义对service传来的消息的处理方法
    public void onServiceConnected(ComponentName name, IBinder service) {
        sMessenger = new Messenger(service);
        System.out.println("fv：connected");

    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        sMessenger = null;
        System.out.println("fv：disconnected");
    }
};
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_ACTION_BAR);
    setContentView(R.layout.food_view_2);
    Intent bs = new Intent(this, ServerObserverService.class);
    bindService(bs, mConnection, Context.BIND_AUTO_CREATE);
}

//处理消息
case R.id.action_service_start:
    String transto = "默认消息";
    Message message = Message.obtain();
    if(item.getTitle().toString().equals("启动实时更新")){
        item.setTitle("停止实时更新");
        message.what = 1;
        Bundle bundle = new Bundle();
        bundle.putString("toService",transto);
        message.setData(bundle);
        message.replyTo = cMessenger;
        try{
            sMessenger.send(message);
            System.out.println("fv:发送消息ed！");
        }catch(RemoteException e){
            e.printStackTrace();
        }
        System.out.println("启动");

    }else{
        item.setTitle("启动实时更新");
        System.out.println("停止");
        message.what = 0;
        Bundle bundle = new Bundle();
        bundle.putString("toService",transto);
        message.setData(bundle);
        message.replyTo = cMessenger;
        try{
            sMessenger.send(message);
            System.out.println("fv:发送消息ed！");
        }catch(RemoteException e){
            e.printStackTrace();
        }
    }
    break;

Manifest中需要注册servicce