flex设置Alert框的位置

//设置弹出框的位置，同时添加事件
		private function handle_AlertMessage(sMessage:String,sTitle:String,flag:int,closeHandler:Function):void
		{
			var alert:Alert = new Alert(); 
			alert.text = sMessage;
			alert.buttonFlags = 3;
  			alert.title = sTitle;
			Alert.yesLabel = "确定";
			Alert.noLabel = "取消";
  			alert.addEventListener(CloseEvent.CLOSE,closeHandler);
			PopUpManager.addPopUp(alert,DisplayObject(this.parentApplication),true); 
			PopUpManager.centerPopUp(alert);
		}