本文转自:http://xwangly.iteye.com/blog/1109424
Messenger:信使
官方文档解释:它引用了一个Handler对象,以便others能够向它发送消息(使用mMessenger.send(Message msg)方法)。该类允许跨进程间基于Message的通信(即两个进程间可以通过Message进行通信),在服务端使用Handler创建一个Messenger,客户端持有这个Messenger就可以与服务端通信了。
以前我们使用Handler+Message的方式进行通信,都是在同一个进程中,从线程持有一个主线程的Handler对象,并向主线程发送消息。
而Android既然可以使用bindler机制进行跨进行通信,所以我们当然可以将Handler与bindler结合起来进行跨进程发送消息。
查看API就可以发现,Messenger就是这种方式的实现。
一般使用方法如下:
1。远程通过
- mMessenger = new Messenger(mHandler)
mMessenger = new Messenger(mHandler)
创建一个信使对象
2。客户端使用bindlerService请求连接远程
3。远程onBind方法返回一个bindler
- return mMessenger.getBinder();
return mMessenger.getBinder();
4.客户端使用远程返回的bindler得到一个信使(即得到远程信使)
- public void onServiceConnected(ComponentName name, IBinder service) {
- rMessenger = new Messenger(service);
- ......
- }
public void onServiceConnected(ComponentName name, IBinder service) {rMessenger = new Messenger(service);......}
这里虽然是new了一个Messenger,但我们查看它的实现
- /**
- * Create a Messenger from a raw IBinder, which had previously been
- * retrieved with {@link #getBinder}.
- *
- * @param target The IBinder this Messenger should communicate with.
- */
- public Messenger(IBinder target) {
- mTarget = IMessenger.Stub.asInterface(target);
- }
/*** Create a Messenger from a raw IBinder, which had previously been* retrieved with {@link #getBinder}.* * @param target The IBinder this Messenger should communicate with.*/public Messenger(IBinder target) {mTarget = IMessenger.Stub.asInterface(target);}
发现它的mTarget是通过Aidl得到的,实际上就是远程创建的那个。
5。客户端可以使用这个远程信使对象向远程发送消息:rMessenger.send(msg);
这样远程服务端的Handler对象就能收到消息了,然后可以在其handlerMessage(Message msg)方法中进行处理。(该Handler对象就是第一步服务端创建Messenger时使用的参数mHandler).
经过这5个步骤貌似只有客户端向服务端发送消息,这样的消息传递是单向的,那么如何实现双向传递呢?
首先需要在第5步稍加修改,在send(msg)前通过msm.replyTo = mMessenger将自己的信使设置到消息中,这样服务端接收到消息时同时也得到了客户端的信使对象了,然后服务端可以通过
- //得到客户端的信使对象,并向它发送消息
- cMessenger = msg.replyTo;
- cMessenger.send(message);
//得到客户端的信使对象,并向它发送消息
cMessenger = msg.replyTo;
cMessenger.send(message);
即完成了从服务端向客户端发送消息的功能,这样客服端可以在自己的Handler对象的handlerMessage方法中接收服务端发送来的message进行处理。
双向通信宣告完成。
下面改写ApiDemos工程实现Messenger通信
MessengerService.java
- package com.xwangly.apidemo.app;
- import java.util.Random;
- import android.app.Service;
- 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.util.Log;
- public class MessengerService extends Service {
- private String TAG = "MessengerService";
- @Override
- public void onDestroy() {
- // TODO Auto-generated method stub
- Log.i(TAG, "onDestroy");
- cMessenger = null;
- super.onDestroy();
- }
- @Override
- public boolean onUnbind(Intent intent) {
- // TODO Auto-generated method stub
- Log.i(TAG, "onUnbind");
- return super.onUnbind(intent);
- }
- static final int MSG_REGISTER_CLIENT = 1;
- static final int MSG_UNREGISTER_CLIENT = 2;
- static final int MSG_SET_VALUE = 3;
- private Random random = new Random();
- private Handler mHandler = new Handler() {
- @Override
- public void handleMessage(Message msg) {
- // TODO Auto-generated method stub
- Log.i(TAG, "handleMessage");
- switch (msg.what) {
- case MSG_SET_VALUE:
- try {
- Message message = Message.obtain(null,
- MessengerService.MSG_SET_VALUE);
- message.arg1 = random.nextInt(100);
- //得到客户端的信使对象,并向它发送消息
- cMessenger = msg.replyTo;
- cMessenger.send(message);
- } catch (RemoteException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- break;
- default:
- super.handleMessage(msg);
- }
- }
- };
- /**
- * 自己的信使对象
- */
- private Messenger mMessenger = new Messenger(mHandler);
- /**
- * 客户的信使
- */
- private Messenger cMessenger;
- @Override
- public IBinder onBind(Intent intent) {
- // TODO Auto-generated method stub
- Log.i(TAG, "onBind");
- //返回自己信使的bindler,以供客户端通过这个bindler得到服务端的信使对象(通过new Messenger(bindler))
- return mMessenger.getBinder();
- }
- @Override
- public void onRebind(Intent intent) {
- // TODO Auto-generated method stub
- Log.i(TAG, "onRebind");
- }
- }
package com.xwangly.apidemo.app;import java.util.Random;import android.app.Service;
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.util.Log;public class MessengerService extends Service {private String TAG = "MessengerService";@Overridepublic void onDestroy() {// TODO Auto-generated method stubLog.i(TAG, "onDestroy");cMessenger = null;super.onDestroy();}@Overridepublic boolean onUnbind(Intent intent) {// TODO Auto-generated method stubLog.i(TAG, "onUnbind");return super.onUnbind(intent);}static final int MSG_REGISTER_CLIENT = 1;static final int MSG_UNREGISTER_CLIENT = 2;static final int MSG_SET_VALUE = 3;private Random random = new Random();private Handler mHandler = new Handler() {@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubLog.i(TAG, "handleMessage");switch (msg.what) {case MSG_SET_VALUE:try {Message message = Message.obtain(null,MessengerService.MSG_SET_VALUE);message.arg1 = random.nextInt(100);//得到客户端的信使对象,并向它发送消息cMessenger = msg.replyTo;cMessenger.send(message);} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}break;default:super.handleMessage(msg);}}};/*** 自己的信使对象*/private Messenger mMessenger = new Messenger(mHandler);/*** 客户的信使*/private Messenger cMessenger;@Overridepublic IBinder onBind(Intent intent) {// TODO Auto-generated method stubLog.i(TAG, "onBind");//返回自己信使的bindler,以供客户端通过这个bindler得到服务端的信使对象(通过new Messenger(bindler))return mMessenger.getBinder();}@Overridepublic void onRebind(Intent intent) {// TODO Auto-generated method stubLog.i(TAG, "onRebind");}}
MessengerServiceActivities.java
- package com.xwangly.apidemo.app;
- import com.xwangly.apidemo.R;
- import android.app.Activity;
- 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.util.Log;
- import android.view.View;
- import android.widget.TextView;
- public class MessengerServiceActivities {
- public static class Binding extends Activity implements
- View.OnClickListener {
- private String TAG = "Binding";
- TextView mCallbackText;
- private boolean isBound;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- setContentView(R.layout.messenger_service_binding);
- findViewById(R.id.bind).setOnClickListener(this);
- findViewById(R.id.unbind).setOnClickListener(this);
- mCallbackText = (TextView) findViewById(R.id.callback);
- mCallbackText.setText("Not attached.");
- }
- private Handler mHandler = new Handler() {
- @Override
- public void handleMessage(Message msg) {
- Log.i(TAG, "handleMessage");
- switch (msg.what) {
- case MessengerService.MSG_SET_VALUE:
- mCallbackText.setText("Received from service: " + msg.arg1);
- break;
- default:
- super.handleMessage(msg);
- }
- }
- };
- /**
- * 自己的信使
- */
- private Messenger mMessenger;
- /**
- * 远程服务的信使
- */
- private Messenger rMessenger;
- private ServiceConnection connection = new ServiceConnection() {
- public void onServiceConnected(ComponentName name, IBinder service) {
- // TODO Auto-generated method stub
- Log.i(TAG, "onServiceConnected");
- rMessenger = new Messenger(service);
- mMessenger = new Messenger(mHandler);
- sendMessage();
- }
- public void onServiceDisconnected(ComponentName name) {
- // TODO Auto-generated method stub
- rMessenger = null;
- }
- };
- public void onClick(View v) {
- // TODO Auto-generated method stub
- Intent intent = new Intent(
- "com.xwangly.apidemo.app.messenger_service");
- switch (v.getId()) {
- case R.id.bind:
- if (!isBound) {
- isBound = bindService(intent, connection, BIND_AUTO_CREATE);
- //isBound = true;
- }else {
- sendMessage();
- }
- break;
- case R.id.unbind:
- if (isBound) {
- unbindService(connection);
- isBound = false;
- }
- break;
- default:
- break;
- }
- }
- /**
- * 使用服务端的信使向它发送一个消息。
- */
- private void sendMessage() {
- // TODO Auto-generated method stub
- Message message = Message.obtain(null, MessengerService.MSG_SET_VALUE);
- message.replyTo = mMessenger;
- try {
- rMessenger.send(message);
- } catch (RemoteException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- }
- }
package com.xwangly.apidemo.app;import com.xwangly.apidemo.R;import android.app.Activity;
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.util.Log;
import android.view.View;
import android.widget.TextView;public class MessengerServiceActivities {public static class Binding extends Activity implementsView.OnClickListener {private String TAG = "Binding";TextView mCallbackText;private boolean isBound;@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);setContentView(R.layout.messenger_service_binding);findViewById(R.id.bind).setOnClickListener(this);findViewById(R.id.unbind).setOnClickListener(this);mCallbackText = (TextView) findViewById(R.id.callback);mCallbackText.setText("Not attached.");}private Handler mHandler = new Handler() {@Overridepublic void handleMessage(Message msg) {Log.i(TAG, "handleMessage");switch (msg.what) {case MessengerService.MSG_SET_VALUE:mCallbackText.setText("Received from service: " + msg.arg1);break;default:super.handleMessage(msg);}}};/*** 自己的信使*/private Messenger mMessenger;/*** 远程服务的信使*/private Messenger rMessenger;private ServiceConnection connection = new ServiceConnection() {public void onServiceConnected(ComponentName name, IBinder service) {// TODO Auto-generated method stubLog.i(TAG, "onServiceConnected");rMessenger = new Messenger(service);mMessenger = new Messenger(mHandler);sendMessage();}public void onServiceDisconnected(ComponentName name) {// TODO Auto-generated method stubrMessenger = null;}};public void onClick(View v) {// TODO Auto-generated method stubIntent intent = new Intent("com.xwangly.apidemo.app.messenger_service");switch (v.getId()) {case R.id.bind:if (!isBound) {isBound = bindService(intent, connection, BIND_AUTO_CREATE);//isBound = true;}else {sendMessage();}break;case R.id.unbind:if (isBound) {unbindService(connection);isBound = false;}break;default:break;}}/*** 使用服务端的信使向它发送一个消息。*/private void sendMessage() {// TODO Auto-generated method stubMessage message = Message.obtain(null, MessengerService.MSG_SET_VALUE);message.replyTo = mMessenger;try {rMessenger.send(message);} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}
AndroidManifest.xml相关配置如下:
- <service android:name=".app.MessengerService" >
- <intent-filter>
- <action android:name="com.xwangly.apidemo.app.messenger_service" />
- </intent-filter>
- </service>
- <activity android:name=".app.MessengerServiceActivities$Binding"
- android:label="@string/activity_messenger_service_binding"
- android:launchMode="singleTop">
- <intent-filter>
- <action android:name="android.intent.action.MAIN" />
- <category android:name="android.intent.category.LAUNCHER" />
- </intent-filter>
- </activity>
<service android:name=".app.MessengerService" ><intent-filter><action android:name="com.xwangly.apidemo.app.messenger_service" /></intent-filter></service><activity android:name=".app.MessengerServiceActivities$Binding"android:label="@string/activity_messenger_service_binding"android:launchMode="singleTop"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity>
至于layout就不帖了,两个按钮一个文本域。