flash as3版本里面用Glist的addItemFromPool报错 is child null

flash as3版本里面用Glist的addItemFromPool报错 is child null
 

_list.removeChildrenToPool();
for (var k:int=0; k < _lvArr.length; k++)
{
var lv:int=config[_lvArr[k]]['nobleLevel'];
if( GameService.myDetail.myDetail.vipchargelevel >= lv)
{
var vitem=_list.addItemFromPool();
vitem.data=_lvArr[k];//lv;
var img:GLoader=vitem.getChild("img").asLoader;
if (img)
{
img.url="ui://viplimit/title" + config[_lvArr[k]]['pic'];
img.data=lv;
}
var idx=_lvArr[k];
var redDot=vitem.getChild('redDot').asImage;
var iconBuy=vitem.getChild('iconBuy').asImage;
var flag:int=checkRedDot(idx);
redDot.visible=flag == 2;
iconBuy.visible=flag == 4;
if (redIdx < 0 && redDot.visible)
{
redIdx=k;
}
if (_selectIdx < 0)
{
var obj=GameService.myDetail.vipChargeGiftObj;
var stime:uint=GConst.MY_LOGIN_INFO.serverTime;
var overTime:uint=obj["timeObj"]["time" + (lv-1)];
//_time=overTime - stime;
_time = 2*60*60-(stime - overTime)%(2*60*60);
FioGlobal.removeOnTimer(countDown);
if (_time > 0 && flag != 2)
{
_list.selectedIndex=k;
_selectIdx=k;
}
}
}
}