Messenger实现Android IPC

标签：android   service   messenger   ipc   

当Service不需要支持并发操作时Messenger会非常有用。Messenger类使用Handler执行每个传入的消息，所有客户端的调用都按顺序运行在同一个线程上，这和AIDL是有区别的，AIDL每个客户端对应一个线程。使用Messenger类还能避免AIDL文件带来的问题，并可以方便地为客户端提供异步消息API。虽然没有那么强大，但该类有时候会很有效，因为它更容易在客户端和Service实现。

下面的例子展示了如何使用Messenger类来提供异步API。首先在onCreate()方法中创建Messenger，然后在onBind()方法中返回Binder对象。当Messenger接受到消息时，它使用存储在replyTo成员变量里的Messenger对象响应客户端的请求。

public class MessengerService extends Service {
    private Handler mMessageHandler;
    private Messenger mMessenger;
    public MessengerService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        return this.mMessenger.getBinder();
    }

    @Override
    public void onCreate() {
        super.onCreate();
        HandlerThread handlerThread=new HandlerThread("MessengerService");
        handlerThread.start();
        this.mMessageHandler=new Handler(handlerThread.getLooper(),new MyhandlerCallback());
        this.mMessenger=new Messenger(this.mMessageHandler);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        this.mMessageHandler.getLooper().quit();
    }

    private class MyhandlerCallback implements Handler.Callback{
        @Override
        public boolean handleMessage(Message msg) {
            boolean delivered=false;
            switch (msg.what){
                case 0:

			//执行具体的任务	
                    delivered=true;
                    break;
                case 1:

			//执行具体的任务
                    break;
            }
            Message reply=Message.obtain(null,2);//生成消息
            try {
                msg.replyTo.send(reply);//反馈给客户端
            } catch (RemoteException e) {
                e.printStackTrace();
            }
            return true;
        }
    }
}

    服务器端配置文件代码如下：
    <service
        android:name=".MessengerService"
        android:enabled="true"
        android:exported="true" >
        <intent-filter>
            <action android:name="com.example.liyuanjing.myapplication.MESSENGER_SERVICE"/>
        </intent-filter>
    </service>

public class MainActivity extends Activity implements ServiceConnection {
    private Button start;
    private Messenger mRemoteMessenger;
    private Messenger mReplyMessenger;
    private Handler mReplyHandler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.start=(Button)findViewById(R.id.start);
        HandlerThread handlerThread=new HandlerThread("ReplyMessenger");
        handlerThread.start();
        this.mReplyHandler=new Handler(handlerThread.getLooper(),new ReplyHandlerCallback());
        this.mReplyMessenger=new Messenger(this.mReplyHandler);
    }

    @Override
    protected void onResume() {
        super.onResume();
        bindService(new Intent("com.example.liyuanjing.myapplication.MESSENGER_SERVICE"),this,BIND_AUTO_CREATE);
    }

    @Override
    protected void onPause() {
        super.onPause();
        unbindService(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        this.mReplyHandler.getLooper().quit();
    }

    public void onSendTextPressed(View v){
        Message message=Message.obtain();
        message.what=0;
        Bundle bundle=new Bundle();
        bundle.putInt("key",1);
        message.obj=bundle;
        message.replyTo=mReplyMessenger;
        try {
            mRemoteMessenger.send(message);
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        this.mRemoteMessenger=new Messenger(service);
        this.start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onSendTextPressed(v);
            }
        });
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        this.mRemoteMessenger=null;
    }
    private class ReplyHandlerCallback implements Handler.Callback{
        @Override
        public boolean handleMessage(Message msg) {
            switch (msg.what){
                case 2:
                    Toast.makeText(MainActivity.this,"接受到了",Toast.LENGTH_LONG).show();
                    break;
            }
            return true;
        }
    }
}

java.lang.RuntimeException: Can‘t marshal non-Parcelable objects across processes.

因为Binder事务传递的数据被称为包裹(Parcel)，必须实现Parcelable接口，否则无法在两个应用之间进行通信。之所以用Bundle传递是因为该类实现了Parcelable接口。当然如果要传递类也必须实现该接口。

Messenger实现Android IPC

标签：android   service   messenger   ipc   

原文地址：http://blog.csdn.net/liyuanjinglyj/article/details/45770241