发送消息未到达活动中的处理程序

Question

I am having the service and activity. inside service i am sending the message. I am trying to catch it inside the main activity. But message is not reaching the handler in activity.

Please see the code below.

Service:

Handler handler = new Handler(Looper.getMainLooper());
    handler.sendEmptyMessage(112345);

MainActivity:

handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Toast.makeText(MainActivity.this, "handled message successfully", Toast.LENGTH_SHORT).show();
            if ( msg.what == 1234 ) {
                Toast.makeText(MainActivity.this, "handled message successfully", Toast.LENGTH_SHORT).show();
            }
        }
    };

Can anyone tell me why it is not reaching the handler in the activity. As far as i know

Answer 1

All messages you are sending using Handler.sendMessageXXX will be handled by the same Handler object. So you have to pass the Handler from Activity to Service . It can be done using Messenger class.

Activity:

public class MyActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        final Handler handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                Toast.makeText(MyActivity.this, "handleMessage " + msg.what, Toast.LENGTH_SHORT).show();
            }
        };

        final Intent intent = new Intent(this, MyService.class);
        final Messenger messenger = new Messenger(handler);

        intent.putExtra("messenger", messenger);
        startService(intent);
    }
}

Service:

public class MyService extends IntentService {
    public MyService() {
        super("");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        final Messenger messenger = (Messenger) intent.getParcelableExtra("messenger");
        final Message message = Message.obtain(null, 1234);


        try {
            messenger.send(message);
        } catch (RemoteException exception) {
            exception.printStackTrace();
        }
    }
}