Android进程通信（IPC）之Messenger

Android中的有IPC有哪些

组件间使用 Intent 传递数据（Bundle）；
文件共享；
Messenger；
AIDL；
ContentProvider；
Broadcast
Socket；

1.如何使用

创建Service

/**
 * //0. 去清单文件中配置service并设置启动action
 */
public class MessengerService extends Service {
    private static final String TAG = "MessengerService";

//    1.创建接受信息的handler
    @SuppressLint("HandlerLeak")
    private Handler msgHandler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            // 4.接口客户端消息
            Bundle data = msg.getData();
            String clientMsg = data.getString("client");
            Log.i(TAG, "客户端消息: "+clientMsg);

            //5.获取Messenger对象发送消息
            Message message = Message.obtain();
            Bundle serviceBundle = new Bundle();
            serviceBundle.putString("service","服务端收到消息");
            message.setData(serviceBundle);
            try {
                Messenger clientMessenger = msg.replyTo;
                clientMessenger.send(message);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }
    };
//    2.创建Messenger对象,并绑定Handler
    private final Messenger mServiceMessenger = new Messenger(msgHandler);

//    3.通过Messenger获取Binder对象
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        // IMessenger.asBinder()
        return mServiceMessenger.getBinder();
    }
}

2.在清单文件注册

<service android:name="[你的包名].main.MessengerService"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
            <action android:name="随便写xxx.MessengerService" />
            </intent-filter>
        </service>

3.接着就去写客户端

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private static final String TAG = "MainActivity";

    public static final String SERVICE_ACTION = "之前服务端清单文件定义的action";
    public static final String SERVICE_PACKED = "你的包名";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.btn1).setOnClickListener(this);
        connectService();
    }

    //1. 绑定service，获得IBinder回调
    ServiceConnection conn = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.i(TAG, "onServiceConnected: " + name);
            //3. 获取服务端的Messenger对象
            Messenger serviceMessenger = new Messenger(service); // 利用Messenger的构造方法获取IMessenger.Stub.asInterface(service);是底层生成好的aidl实现类IMessenger
            //4. 准备消息
            Message message = Message.obtain();
            Bundle b = new Bundle();
            b.putString("client", "服务端你好，我是客户端");
            message.setData(b);

            //7.在消息中添加客户端回复入口Messenger，Optional Messenger where replies to this message can be sent.
            message.replyTo = mClientMessenger;
            //8.发送消息，通过IMessenger发送消息
            try {
                serviceMessenger.send(message);
            } catch (RemoteException e) {
                e.printStackTrace();
            }

        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.i(TAG, "onServiceDisconnected: " + name);
        }
    };

    //2. 绑定服务端服务
    private void connectService() {
        Intent intent = new Intent(SERVICE_ACTION);
        intent.setPackage(SERVICE_PACKED);
        boolean b = bindService(intent, conn, Context.BIND_AUTO_CREATE);
        Log.i(TAG, "connectService: 绑定服务 " + b);
    }

    //5 创建客户端接受消息的handler
    @SuppressLint("HandlerLeak")
    private Handler handler = new Handler() {
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            Bundle bundle = msg.getData();
            String service = bundle.getString("service");
            Log.i(TAG, "服务端的回复： " + service);

        }
    };

    //6.创建客户端Messenger，并绑定handler
    private Messenger mClientMessenger = new Messenger(handler);

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn1:
                connectService();
                break;
            default:
                break;
        }

    }

    @Override
    protected void onDestroy() {
        unbindService(conn);
        super.onDestroy();
    }
}

原理

Messenger底层也是通过aidl实现，不过封装了一层，aidl支持多线程并发。messenger是同步，如果没有多线程并发要求，就可以使用轻量级的Messenger

参考：https://blog.csdn.net/chrislanbo/article/details/126343184