cocos2dx 3.3 quick lua 實現返回鍵退出程序

<span style="font-size:18px;">    local layer = display.newLayer()    
    self:addChild(layer,-10)  
    layer:setKeypadEnabled(true)  
    layer:addNodeEventListener(cc.KEYPAD_EVENT, function (event)  
        if event.key == "back" then  --返回鍵
            print("back")  --彈出一個對話框，點擊yes退出程序
            device.showAlert("Confirm Exit", "Are you sure exit game ?", {"YES", "NO"}, function (event)

                if event.buttonIndex == 1 then  
                    cc.Director:getInstance():endToLua()
                else  
                    device.cancelAlert()  --取消對話框 
                end  
            end)           
        elseif event.key == "menu" then  --菜單鍵
            print("menu")               
        end        
    end) </span>