rosandroid tutorial_pubsub connection bewteen RosTextView and Talker-message

edit

Could you indicate what wasn't clear in the extended answer to your previous question?

If you want the actual source, see RosTextView.java in org.ros.android.view, lines 68 to 92 (this is the Hydro version):

public void onStart(ConnectedNode connectedNode) {
  Subscriber<T> subscriber = connectedNode.newSubscriber(topicName, messageType);
  subscriber.addMessageListener(new MessageListener<T>() {
    @Override
    public void onNewMessage(final T message) {
      if (callable != null) {
        post(new Runnable() {
          @Override
          public void run() {
            setText(callable.call(message));
          }
        });
      } else {
        post(new Runnable() {
          @Override
          public void run() {
            setText(message.toString());
          }
        });
      }
      postInvalidate();
    }
  });
}

The onNewMessage(..) method essentially calls the callback registered earlier by the user, which in the case of a std_msgs::String could just return the string itself.

Btw: you might be interested in the ROS Java Special Interest Group.