<service android:name=".CustomService" android:process=":remote"/>

public class CustomService extends Service{
  static final int MSG_SAY_HELLO = 1;
  //实现一个能够处理接收信息的Handler
  class IncomingHandler extends Handler{
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      switch(msg.what){
        case MSG_SAY_HELLO:
          Toast.makeText(getApplicationContext(),"hello!",Toast.LENGTH_SHORT).show();
          break;
        default:
          super.handleMessage(msg);
      }
    }
  }
  //被客户端接收的Messenger对象
  final Messenger messenger = new Messenger(new IncomingHandler());
  @Override
  public IBinder onBind(Intent intent) {
    Toast.makeText(getApplicationContext(),"binding!",Toast.LENGTH_SHORT).show();
    return messenger.getBinder();
  }
}

public class MainActivity extends AppCompatActivity {
  private Button mBtStart;
  private Messenger messenger = null;
  private boolean mBound;
  private TextView mTvMsg;
  private ServiceConnection serviceConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      messenger = new Messenger(service);
      mBound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
      messenger = null;
      mBound = false;
    }
  };
  public void sayHello(View v){
    if(!mBound) return;
    Message msg = Message.obtain(null,CustomService.MSG_SAY_HELLO,0,0);
    try{
      messenger.send(msg);
    }catch (RemoteException e){
      e.printStackTrace();
    }
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mBtStart = (Button) findViewById(R.id.bt_start);
    mTvMsg = (TextView) findViewById(R.id.tv_msg);
    mBtStart.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        Intent intent = new Intent(MainActivity.this,CustomService.class);
        bindService(new Intent(MainActivity.this,CustomService.class),serviceConnection, Context.BIND_AUTO_CREATE);
      }
    });
  }
  @Override
  protected void onStop() {
    super.onStop();
    // Unbind from the service
    if (mBound) {
      unbindService(serviceConnection);
      mBound = false;
    }
  }
}

clientMessenger = msg.replyTo;//这个Message是在客户端中创建的
        if(clientMessenger!=null){
          Message msgToClient = Message.obtain();
          msgToClient.what = SEND_MESSAGE_CODE;
          Bundle bundle = new Bundle();
          bundle.putString("msg","客户端，我接收到你的消息了，这是我回应给你的，看到了吗？");
          msgToClient.setData(bundle);
          try {
            clientMessenger.send(msgToClient);
          } catch (RemoteException e) {
            e.printStackTrace();
          }
        }

public class MyService extends Service {
  private static final int RECEIVE_MESSAGE_CODE = 0x0001;
  private static final int SEND_MESSAGE_CODE = 0x0002;

  private Messenger clientMessenger = null;
  private Messenger serviceMessenger = new Messenger(new ServiceHandler());
  @Override
  public IBinder onBind(Intent intent) {
    return serviceMessenger.getBinder();
  }

  @Override
  public void onCreate() {
    super.onCreate();
  }

  @Override
  public void onDestroy() {
    super.onDestroy();
    clientMessenger = null;
  }

  private class ServiceHandler extends Handler{
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      if(msg.what == RECEIVE_MESSAGE_CODE){
        Bundle data = msg.getData();
        if(data != null){
          String str = data.getString("msg");
          Toast.makeText(getApplicationContext(),"Service:I received the message:"+str,Toast.LENGTH_SHORT).show();
        }
        clientMessenger = msg.replyTo;//这个Message是在客户端中创建的
        if(clientMessenger!=null){
          Message msgToClient = Message.obtain();
          msgToClient.what = SEND_MESSAGE_CODE;
          Bundle bundle = new Bundle();
          bundle.putString("msg","客户端，我接收到你的消息了，这是我回应给你的，看到了吗？");
          msgToClient.setData(bundle);
          try {
            clientMessenger.send(msgToClient);
          } catch (RemoteException e) {
            e.printStackTrace();
          }
        }
      }

    }
  }
}

public class MainActivity extends AppCompatActivity{
  private Button mBtBind;
  private Button mBtUnBind;
  private TextView mTvMsg;

  private static final int SEND_MESSAGE_CODE = 0x0001;
  private static final int RECEIVE_MESSAGE_CODE = 0x0002;
  private boolean isBound = false;

  private String SERVICE_ACTION = "com.example.serviceapp.MyService";

  private Messenger serviceMessenger = null;

  private Messenger clientMessenger = new Messenger(new ClientHandler());
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mBtBind = (Button) findViewById(R.id.bt_bind);
    mBtUnBind = (Button) findViewById(R.id.bt_unbind);
    mTvMsg = (TextView) findViewById(R.id.tv_msg);
    mBtUnBind.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        if(isBound){
          unbindService(serviceConnection);
        }
      }
    });
    mBtBind.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        if(!isBound){
          Intent intent = new Intent();
          intent.setAction(SERVICE_ACTION);
          intent.addCategory(Intent.CATEGORY_DEFAULT);
          PackageManager pm = getPackageManager();
          ResolveInfo info = pm.resolveService(intent,0);
          if(info != null){
            String packageName = info.serviceInfo.packageName;
            String serviceName = info.serviceInfo.name;
            ComponentName componentName = new ComponentName(packageName,serviceName);
            intent.setComponent(componentName);
            bindService(intent,serviceConnection,BIND_AUTO_CREATE);
          }
        }
      }
    });
  }
  private ServiceConnection serviceConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      serviceMessenger = new Messenger(service);
      isBound = true;
      Message msg = Message.obtain();
      msg.what = SEND_MESSAGE_CODE;
      Bundle data = new Bundle();
      data.putString("msg","你好，MyService，我是客户端");
      msg.setData(data);
      msg.replyTo = clientMessenger;
      try {
        serviceMessenger.send(msg);
      } catch (RemoteException e) {
        e.printStackTrace();
      }
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
      serviceMessenger = null;
      isBound = false;
    }
  };
  private class ClientHandler extends Handler{
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      if(msg.what == RECEIVE_MESSAGE_CODE){
        Bundle data = msg.getData();
        if(data != null){
          String str = data.getString("msg");
          mTvMsg.setText(str);
        }
      }
    }
  }
}