cocos-lua 键盘监听事件

cocos-lua键盘监听事件，按下和弹起

function GameTest:init_keyboard()

      local function onKeyPressed(keyCode, event)

      end

      local function onKeyReleased(keyCode, event)

      end

      local listener = cc.EventListenerKeyboard:create()
      listener:registerScriptHandler(onKeyPressed, cc.Handler.EVENT_KEYBOARD_PRESSED)  
      listener:registerScriptHandler(onKeyReleased, cc.Handler.EVENT_KEYBOARD_RELEASED)
      cc.Director:getInstance():getEventDispatcher():addEventListenerWithSceneGraphPriority(listener, self) 

end

self是一个场景