flex as mxml 之间引用关系

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" xmlns:panels2="demo.flexinaction.samples.*" layout="absolute" initialize="doInit();">
<mx:Script>
   <![CDATA[
   import demo.flexinaction.samples.*;
    private function doInit():void{
    var panelC:CustomPanelAS=new CustomPanelAS();
    panelC.title="hello";
        hbox.addChild(panelC);
        var panelD:CustomPanelMXML=new CustomPanelMXML();
        panelD.title="zhuwenqi";
        hbox.addChild(panelD);
       panelA.buttonID.label="sssssssssss";
     
    }
   
   ]]>
</mx:Script>
<mx:VBox id="hbox" width="407" height="414">
    <panels2:CustomPanelAS id="panelB" title="CustomPanelrenderedbyActionScript"/>
<panels2:CustomPanelMXML id="panelA" title="CustomPanelrenderedbyActionScript"/>
</mx:VBox>
</mx:Application>