Keyboard processing can be another example of CC_CALLBACK usage.

If you want to process keyboard you should add following code to scene’s init method:

// keyboard processing
EventListenerKeyboard* sceneKeyboardListener = EventListenerKeyboard::create();
sceneKeyboardListener->onKeyPressed = CC_CALLBACK_2(ActionsDemoScene::onKeyPressedScene, this);
_eventDispatcher->addEventListenerWithSceneGraphPriority(sceneKeyboardListener, this);

Now the actual processing looks like this:

void ActionsDemoScene::onKeyPressedScene(EventKeyboard::KeyCode keyCode,
                                         Event                 *event) {
  printf("%s: processing key %d pressed\n", __func__, (int)keyCode);

  if (EventKeyboard::KeyCode::KEY_A == keyCode) {
    printf("%s: key 'a' was pressed\n", __func__);
  }
  else {
    printf("%s: failed to process.\n", __func__);
  }
}

First, we create an instance of EventListenerKeyboard. That’s a very small class that has tow pointers to functions: onKeyPressed and onKeyReleased. For now, we’ll use only one of them. The method that will process the event will receive two parameters, so we use CC_CALLBACK_2 macro.

Then we pass newly created object to global EventDispatcher instance responsible for processing all events.

Actually, there is no need to process keyboard events in the scene method. You can create and register a lot of these methods wherever you need. I just suppose it’s a bit better to keep all of them in one place.