PopUpManager在产生TitleWindow时应记录当前的TitleWindow，目前只能通过1）获取
1) var titleWindowInstance:TitleWindowData = TitleWindowData(PopUpManager.createPopUp(this, TitleWindowData, false));
PopUpManager.centerPopUp(titleWindowInstance);
//TitleWindowData 获取parent
titleWindowInstance.mainApp = this;
2)PopUpManager.addPopUp(new TitleWindowData,this, false)