Android基础——Service IPC通讯（Messenger实现）

Messager实现IPC通信，底层也是使用了AIDL方式。和AIDL方式不同的是，Messager方式是利用Handler形式处理，因此，它是线程安全的，这也表示它不支持并发处理；而AIDL方式是非线程安全的，支持并发处理，因此，我们使用AIDL方式时需要保证代码的线程安全。大部分情况下，我们应用中不需要并发处理。因此，我们通常只需要使用Messager方式。

在我们的例子中：ClientActivity和Service分数不同的进程，我们在Client绑定Service的时候可以获得Service端的Messenger，在Client端通过Messenger发送消息到Service端，将消息交给handler 去处理，同样Service端也可以通过Client端的Messenger进行同样的操作。

为了让Service运行在其他的进程，我们需要在Manifest.xml中做一些设置：

<service
            android:name="com.flyingduck.servicedemo2.MessengerService"
            android:process=":remote" >
        </service>

android:name=“:remote”写法是任意的，可以写成其他的字符串，但是必须要加上‘：’的前缀。

客户端进程：

package com.flyingduck.servicedemo2;

import android.app.Activity;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
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.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class ClientActivity extends Activity {

	private TextView showTxt;
	private Button sendMsg;
	private Button boundBtn;
	private Button unboundBtn;

	private ServiceConnection conn;

	private final Messenger mMessenger = new Messenger(new IncomingHandler());

	/** 服务端的Messenger **/
	private Messenger serviceMessenger;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_client);
		showTxt = (TextView) findViewById(R.id.show_message);
		sendMsg = (Button) findViewById(R.id.send_set_value_message);
		boundBtn = (Button) findViewById(R.id.bound_service);
		unboundBtn = (Button) findViewById(R.id.unbound_service);

		boundBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				doInBindService();
			}
		});
		unboundBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				doInUnBindService();
			}
		});
		sendMsg.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View arg0) {
				showTxt.setText("send set_value_message");
				if (serviceMessenger != null) {
					try {
						// 发送一个100 值到service
						Message msg = Message.obtain(null,
								MessengerService.MSG_SET_VALUE, 100, 0);
						msg.replyTo = mMessenger;
						serviceMessenger.send(msg);
					} catch (RemoteException e) {
						e.printStackTrace();
					}
				}
			}
		});

		conn = new ServiceConnection() {

			@Override
			public void onServiceDisconnected(ComponentName name) {
				showTxt.setText("disconnectes");
			}

			@Override
			public void onServiceConnected(ComponentName name, IBinder service) {
				serviceMessenger = new Messenger(service);
				showTxt.setText("connectes");
				try {
					Message msg = Message.obtain(null,
							MessengerService.MSG_REGISTER_CLIENT);
					msg.replyTo = mMessenger;
					serviceMessenger.send(msg);
				} catch (RemoteException e) {
					e.printStackTrace();
				}
			}
		};

	}

	private void doInBindService() {
		showTxt.setText("bind");
		bindService(new Intent(this, MessengerService.class), conn,
				Service.BIND_AUTO_CREATE);
	}

	private void doInUnBindService() {
		showTxt.setText("unbind");
		unbindService(conn);

		if (serviceMessenger != null) {
			try {
				Message msg = Message.obtain(null,
						MessengerService.MSG_UNREGISTER_CLIENT);
				msg.replyTo = mMessenger;
				serviceMessenger.send(msg);
			} catch (RemoteException e) {
				e.printStackTrace();
			}
		}
	}

	/** 用于处理服务发过来的消息 **/
	class IncomingHandler extends Handler {
		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case MessengerService.MSG_SET_VALUE:
				showTxt.setText("received from service:" + msg.arg1);
				break;
			default:
				super.handleMessage(msg);
			}
		}
	}

}

Service端：

package com.flyingduck.servicedemo2;

import java.util.ArrayList;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.widget.Toast;

public class MessengerService extends Service {

	private NotificationManager notifyM;
	/** 用于记录所有绑定service的客户端 这里只有一个client绑定这个service**/
	ArrayList<Messenger> clients = new ArrayList<Messenger>();

	private final Messenger mMessenger = new Messenger(new IncomingHandler());

	/** 定义几种Handler的消息类型 **/
	static final int MSG_REGISTER_CLIENT = 1;
	static final int MSG_UNREGISTER_CLIENT = 2;
	static final int MSG_SET_VALUE = 3;

	/** 用于发送消息时使用 **/
	private int value = 100;

	/** 用于处理客户端发过来的消息 **/
	class IncomingHandler extends Handler {

		@Override
		public void handleMessage(Message msg) {

			switch (msg.what) {
			case MSG_REGISTER_CLIENT:
				clients.add(msg.replyTo);
				break;
			case MSG_UNREGISTER_CLIENT:
				clients.remove(msg.replyTo);
				break;
			case MSG_SET_VALUE:
				for (int index = clients.size() - 1; index >= 0; index--) {
					try {
						//接收到ClientActivity发送过来的值“100”，再加上value ，发送给ActivityClient
						clients.get(index).send(
								Message.obtain(null, MSG_SET_VALUE, value+msg.arg1, 0));
					} catch (RemoteException e) {
						clients.remove(index);
					}

				}
				break;
			default:
				super.handleMessage(msg);
				break;
			}
		}
	}

	@Override
	public void onCreate() {
		notifyM = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
		showNotification();
	}

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

	private void onDestor() {
		notifyM.cancel(100);
		Toast.makeText(this, "service distory", Toast.LENGTH_SHORT).show();
	}

	private void showNotification() {
		Notification notification = new Notification(R.drawable.ic_launcher,
				"Service start...", System.currentTimeMillis());
		notification.setLatestEventInfo(this, "content-title",
				"service started", null);
		notifyM.notify(100, notification);
	}

}

client 发送了一个100整数给service端，service将 其加上100发送给client端显示。

运行截图：