加载界面功能逻辑

嵌套调用：
1.方法A调用方法B
2.B调A
3.A or B里面设置终止条件

--假如有以下文件需要预加载
local PLIST_FILE = {
    "res/Image/res_game",
    "res/Image/res_ui",
}
function LoadingScene:ctor()
  self:updateLoadRes()
end
function LoadingScene:updateLoadRes()
    self:runAction(cc.Sequence:create(cc.DelayTime:create(self.per_time),cc.CallFunc:create(function(sender)
        display.loadImage(PLIST_FILE[self.loadResNum]..".png", handler(self, self.loadResCallBack))
    end)))
end
  
function LoadingScene:loadResCallBack(texture)
    local plistName = PLIST_FILE[self.loadResNum]..".plist"
    --加载plist文件
    cc.SpriteFrameCache:getInstance():addSpriteFrames(plistName)
    local nowPercent = math.min(100, 100*(self.loadResNum/#PLIST_FILE))
    self.lod_bar:setPercent(nowPercent)  --如果有进度条，更新百分比

    if self.loadResNum >= #PLIST_FILE then
        print("资源加载完成")     
        self:runAction(cc.Sequence:create(cc.DelayTime:create(0.5),cc.CallFunc:create(function(sender)
            local StartScene = require("app/views/StartScene"):create(true)
            cc.Director:getInstance():replaceScene(StartScene)   
        end)))
        return
    end
    self.loadResNum = self.loadResNum + 1

    self:updateLoadRes()
end