Detailed explanation of two-way communication between Android Messenger processes
Before implementing Messenger communication, we must first complete a prerequisite: bind a component to the service by calling bindService (). This is what we have to do to bind the component to the service:
http://blog.csdn.net/q296264785/article/details/53418534 To
bind the client to the service, you must:
1、实现ServiceConnection。
你的实现代码必须重写两个回调方法：
onServiceConnected()
系统调用该方法来传递服务的onBind()方法所返回的IBinder。
onServiceDisconnected()
当与服务的联接发生意外中断时，比如服务崩溃或者被杀死时，Android系统将会调用该方法。客户端解除绑定时，不会调用该方法。
private ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
// TODO Auto-generated method stub
}
};2、调用bindService()，传入已实现的ServiceConnection。
@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
Intent intent = new Intent(this, MService.class);
bindService(intent, conn, IBinder.LAST_CALL_TRANSACTION);
}3、当系统调用你的onServiceConnected()回调方法时，你可以利用接口中定义的方法开始对服务的调用。
4、要断开与服务的联接，请调用unbindService()。
—————————————- I am the dividing line, the following starts data communication —————————-
Through the above steps, we have completed the determination of Service, and then we can achieve data communication. For easy understanding, we first implement one-way communication: Activity sends data to Service, here is the official API to communicate Things to do:
1、服务实现一个Handler ，用于客户端每次调用时接收回调。
2、此Handler用于创建一个Messenger对象（它是一个对Handler的引用)。
3、此Messenger对象创建一个IBinder，服务在onBind()中把它返回给客户端。
4、客户端用IBinder将Messenger（引用服务的Handler）实例化，客户端用它向服务发送消息对象Message。
5、服务接收Handler中的每个消息Message——确切的说，是在handleMessage()方法中接收。
Let's write the implementation class of Service first. After reading the above five points, the services that need to be implemented are: 1, 2, 3, and 5.
//1、服务实现一个Handler ，用于客户端每次调用时接收回调。
class MHandler extends Handler {}//2、此Handler用于创建一个Messenger对象（它是一个对Handler的引用)。
Messenger messenger = new Messenger(new MHandler());//3、此Messenger对象创建一个IBinder，服务在onBind()中把它返回给客户端。
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return messenger.getBinder();
}//5、服务接收Handler中的每个消息Message——确切的说，是在handleMessage()方法中接收。
class MHandler extends Handler {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
if (msg.what == 1) {
System.out.println("--从Activity接受到的数据->>"
+ msg.getData().getString("NUM"));
//Toast打印数据
Toast.makeText(getApplicationContext(), "接收到数据", 1).show();
}
}
}At this point, all the things we need to do in Service are done. Next is what the Activity needs to do:
//4、客户端用IBinder将Messenger（引用服务的Handler）实例化
private ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
messenger = new Messenger(service);
}
};
//客户端用它（messenger ）向服务发送消息对象Message。
Message message = Message.obtain(null, 1); //获得消息载体
Bundle data = new Bundle();
data.putString("NUM", "Activity信使");
message.setData(data);//写入数据
try {
messenger.send(message);//发送数据
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}Here we have completed the one-way communication of Activity to Service, the principle of two-way communication and one-way communication is basically the same.
Start with the sending end (Service), in Service we need to add a piece of code to send data:
// 1、通过msg.replyTo获得Activity中message.replyTo = replyMessenger赋值的Messenger。
Messenger messenger1 = msg.replyTo;
Message message = Message.obtain(null, 2); // 2、获得一个Message，写入需要传递的数据。
Bundle data = new Bundle();
data.putString("NUM", "Service信使");
message.setData(data);
try {
messenger1.send(message);// 3、发送数据
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}We need to write another piece of data receiving code in Activity, the code is basically the same as the receiving code in Service just now, the receiving activity:
private Messenger replyMessenger = new Messenger(new Handler() {// 1、创建一个Handler实现并且通过这个实现创建一个Messenger的实现
public void handleMessage(Message msg) {
switch (msg.what) {
case 2:
// 获取信息内容并Toast
Toast.makeText(MainActivity.this,
msg.getData().getString("NUM"), 0).show();// 3、获取Service传递过来的值
break;
default:
break;
}
};
});message.replyTo = replyMessenger;// 2、将1获得的实现传递给replyToAll source code:
The layout file only needs a Button
<Button
android:id="@+id/MSG_button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/button2"
android:layout_centerHorizontal="true"
android:layout_marginTop="40dp"
android:text="向Service发送数据" />MainActivity:
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.view.View;
import android.view.View.OnClickListener;
import android.widget.Toast;
public class MainActivity extends Activity {
private Messenger messenger;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.MSG_button1).setOnClickListener(
new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Message message = Message.obtain(null, 1);
Bundle data = new Bundle();
data.putString("NUM", "Activity信使");
message.setData(data);
// -------------
message.replyTo = replyMessenger;// 2、将1获得的实现传递给replyTo
try {
messenger.send(message);
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
private Messenger replyMessenger = new Messenger(new Handler() {// 1、创建一个Handler实现并且通过这个实现创建一个Messenger的实现
public void handleMessage(Message msg) {
switch (msg.what) {
case 2:
// 获取信息内容并Toast
Toast.makeText(MainActivity.this,
msg.getData().getString("NUM"), 0).show();// 3、获取Service传递过来的值
break;
default:
break;
}
};
});
@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
Intent intent = new Intent(this, MService.class);
bindService(intent, conn, IBinder.LAST_CALL_TRANSACTION);
}
private ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
// TODO Auto-generated method stub
messenger = new Messenger(service);
}
};
}MService：
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.widget.Toast;
public class MService extends Service {
class MHandler extends Handler {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
if (msg.what == 1) {
System.out.println("--从Activity接受到的数据->>"
+ msg.getData().getString("NUM"));
Toast.makeText(getApplicationContext(), "接收到数据", 1).show();
// ----------------------------------------------
// 1、通过msg.replyTo获得Activity中message.replyTo = replyMessenger赋值的Messenger。
Messenger messenger1 = msg.replyTo;
Message message = Message.obtain(null, 2); // 2、获得一个Message，写入需要传递的数据。
Bundle data = new Bundle();
data.putString("NUM", "Service信使");
message.setData(data);
try {
messenger1.send(message);// 3、发送数据
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
Messenger messenger = new Messenger(new MHandler());
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return messenger.getBinder();
}
}
