解决 FLex 4.0 Module里面Alert.show();出错问题

TypeError: Error #1009: 无法访问空对象引用的属性或方法。
at mx.managers::PopUpManagerImpl/http://www.adobe.com/2006/flex/mx/internal::createModalWindow()[E:\dev\hero_private\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:701]
at mx.managers::PopUpManagerImpl/addPopUp()[E:\dev\hero_private\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:400]
at mx.managers::PopUpManager$/addPopUp()[E:\dev\hero_private\frameworks\projects\framework\src\mx\managers\PopUpManager.as:193]
at mx.controls::Alert$/show()[E:\dev\hero_private\frameworks\projects\mx\src\mx\controls\Alert.as:618]

解决方法：

在Application文件里添加

import mx.managers.PopUpManager;

private var pop:PopUpManager=new PopUpManager();即可

同时Alert.show("text", "title", Alert.OK, this);前4个参数不可默认。