如何实现字幕效果，cocos2dx ，Lua

条条大路通罗马，其实实现的方法有多种，下面我就写2种吧。。

第1种：通过ClippingNode画一个遮罩即可完成，带遮罩内部显示，外部隐藏.

local NoticeBg  = self:getWidget("Image_notice")  
    local NoticeBgW = NoticeBg:getContentSize().width   
    local NoticeBgH = NoticeBg:getContentSize().height  
    local OrgX = - NoticeBgW / 2  
    local OrgY = NoticeBgH / 2 
    local DesX = NoticeBgW + 100  
    local DesY = NoticeBgH / 2 
      
    local voice_icon = self:getWidget("Image_voice") --呐吧  
  
    local text = cc.Label:createWithTTF("首次充值将会活动额外奖励", "zhunyuan.ttf", 26)  
    text:setPosition(cc.p(OrgX, OrgY))  
    text:setAnchorPoint(0,0.5)
    text:setColor(cc.c3b(255,255,255))
  
    local clip = cc.ClippingNode:create()  
    NoticeBg:addChild(clip)  
  
    -- --以下模型是带图像遮罩  
    local bgSharp = cc.DrawNode:create()  
    local beginX = voice_icon:getPositionX()+voice_icon:getContentSize().width  
    local Point = {  
        [1] = cc.p(beginX / 2, 0),  
        [2] = cc.p(NoticeBgW - beginX, 0),  
        [3] = cc.p(NoticeBgW - beginX, NoticeBgH),  
        [4] = cc.p(beginX / 2, NoticeBgH),  
    }  
    bgSharp:drawPolygon(Point, 4, cc.c4f(1, 0, 0, 1), 2, cc.c4f(0, 1, 0, 1))  
    clip:setStencil(bgSharp)  
    clip:setAnchorPoint(cc.p(0.5, 0.5))  
    clip:setPosition(beginX / 2, 0)  
    clip:addChild(text)  
  
    local function displayAdvise()  
        if text:getPositionX()+text:getContentSize().width+10 <  0 then  
            --todo  
            text:setPosition(cc.p(DesX, DesY))  
        else  
            text:setPositionX(text:getPositionX() - 3) --移动速度 
        end  
    end  
   self.schedu = scheduler:scheduleScriptFunc(displayAdvise, 0.01, false) 

self._scrollView = self:getWidget("ScrollView_2")
	self._scrollText = self._scrollView:getChildByName("Text_3")
	self._scrollText:setText("我是测试公告我是测试公告")
	local posX,posY = self._scrollText:getPosition()
	local function callback()
		self._scrollText:setPosition(posX,posY)
		self._scrollText:moveTo({x=-200,y=self._scrollText:getPositionY(),time=10,onComplete=callback})
	end
	self._scrollText:moveTo({x=-200,y=self._scrollText:getPositionY(),time=10,onComplete=callback})