一、Messenger类
作用：类似Message类，但是是跨进程使用的。
解析：它的底层是由AIDL实现的，从构造方法可以看出
//Service使用
public Messenger(Handler target){
mTarget = target.getIMessenger();
}
//Client端使用
public Messenger(IBinder targer){
mTarget = IMessenger.Stub.asInterface(target);
}
二、使用（Service与Client互相发送信息）
步骤一：Service端创建Messenger
public class BookService extends Service {
private static final String TAG = "BookService";
//①：创建Handler，为创建Messenger做准备
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what){
case 0:
//当客户端发送信息的时候吗，输出
Bundle bundle = msg.getData();
Log.d(TAG,"Service收到消息"+bundle.getString("msg"));
break;
}
}
};
//②：创建Messenger
private Messenger mMessenger = new Messenger(mHandler);
@Override
public void onCreate() {
super.onCreate();
}
@Override
public IBinder onBind(Intent intent) {
//③：将Messenger对象的Binder返回给Client
return mMessenger.getBinder();
}
}
步骤二：Client端接收Messenger发送信息给Service端
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private Messenger mService;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ServiceConnection connection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
//重新创建Messenger
mService = new Messenger(service);
//从Msg池中获取message
Message msg = Message.obtain(null,0);
//创建Bundle
Bundle bundle = new Bundle();
bundle.putString("msg","Hello,nice to meet you");
//将Bundle装进message对象中
msg.setData(bundle);
try {
//将message发送给服务端,同时说明Message继承了Parcelable接口
mService.send(msg);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
Intent intent = new Intent(this,BookService.class);
bindService(intent, connection, BIND_AUTO_CREATE);
}
步骤三：实现服务器向客户端发送信息的双向交流
//Client端 /**
*第一步：创建Handler接收服务器发送过来的信息
*/
private Handler mHandler = new Handler(){ @Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what){
case 0:
Bundle bundle = msg.getData();
Log.d(TAG,"客户端接收到信息："+bundle.getString("replyData"));
break;
}
}
}; /**
*第二步：在 public void onServiceConnected(ComponentName name, IBinder service) 方法中添加
*/
msg.replyTo = mService;
/**
*Service端的Handler中
*/
//在Handler中接收到Client中传送过来的Messenger
Messenger messenger = msg.replyTo;
//创建Msg
Message replyMessage = Message.obtain(null,0);
try {
//将Msg发送回给Client
messenger.send(replyMessage);
} catch (RemoteException e) {
e.printStackTrace();
}
流程图
