Flex弹出层

<?xml version="1.0"?>
<mx:Application xmlns:mx=" http://www.adobe.com/2006/mxml">
    <mx:Script>
    import mx.events.CloseEvent;
    import mx.containers.TitleWindow;
    import mx.containers.Panel;
    import mx.managers.PopUpManager;
    import mx.controls.TextArea;
    import mx.core.IFlexDisplayObject;
 import mx.controls.Alert;
   
    public function openWindow(event:MouseEvent):void {
        var myPopUp:TextArea;myPopUp = new TextArea();
        myPopUp.width= 220;
        myPopUp.height= 150;
        myPopUp.setStyle("fontSize",12);
        myPopUp.setStyle("backgroundAlpha",0.5);
        var panel:TitleWindow=new TitleWindow();
        panel.showCloseButton=true;
        panel.addEventListener(CloseEvent.CLOSE,closeWin);
        panel.title="Comments";
        panel.setStyle("backgroundAlpha",0);
        panel.setStyle("fontSize",12);
        panel.addChild(myPopUp);
        PopUpManager.addPopUp(panel, this, true);
        PopUpManager.centerPopUp(panel);
    }
    private function closeWin(event:CloseEvent):void{
     PopUpManager.removePopUp(IFlexDisplayObject(event.currentTarget));
    }
   
    </mx:Script>
    <mx:VBox>
        <mx:Button id="b1" label="Create TextArea Popup" click="openWindow(event);"/>
    </mx:VBox>
</mx:Application>