TabBar 隐藏掉ViewStack中的一项

Flex 中TabBar 和ViewStack 结合使用，如果ViewStack中的NavigatorContent 为includeInLayout 为false,现在也希望TabBar能够隐藏掉相应的button。现有的TabBar不能满足条件，只能继承来做一些修改。

package
{
	import mx.core.IVisualElement;
	
	import spark.components.TabBar;
	
	public class SuperTabBar extends TabBar
	{
		public function SuperTabBar()
		{
			super();
		}
		
		override public function updateRenderer(renderer:IVisualElement,itemIndex:int,data:Object):void
		{
			super.updateRenderer(renderer,itemIndex,data);
			const content:IVisualElement = getItemContent(itemIndex) as IVisualElement;
			if(content && !content.includeInLayout)
			{
				renderer.visible = false;
				renderer.includeInLayout = false;
                  if(itemIndex == 0)
				{
					itemSelected(1,true);
				}
			}
		}
		
		private function getItemContent(index:int):IVisualElement
		{
			if (!dataGroup || (index < 0) || (index >= dataGroup.numElements))
				return null;
			if(!dataGroup.dataProvider || index >= dataGroup.dataProvider.length)
				return null;
			return dataGroup.dataProvider.getItemAt(index) as IVisualElement;
		}
	}
}

?测试代码

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
			   xmlns:s="library://ns.adobe.com/flex/spark" 
			   xmlns:mx="library://ns.adobe.com/flex/mx"
			   xmlns:controls="com.lombardrisk.report.lbr.components.controls.*"
			   minWidth="955" minHeight="600" xmlns:local="*">
	<fx:Script>
		<![CDATA[

		]]>
	</fx:Script>
	<s:layout>
		<s:VerticalLayout/>
	</s:layout>
	<local:SuperTabBar id="tabBar" dataProvider="{viewStack}"/>
	<mx:ViewStack id="viewStack" width="100%" creationPolicy="all">
		<s:NavigatorContent label="aaa">
			<s:Button label="aaaa"/>
		</s:NavigatorContent>
		<s:NavigatorContent label="bbb">
			<s:Button label="bbbb"/>
		</s:NavigatorContent>
		<s:NavigatorContent label="ccc" includeInLayout="false" visible="false" enabled="true">
			<s:Button label="cccc"/>
		</s:NavigatorContent>
	</mx:ViewStack>
</s:Application>

?会发现ccc的button不会出现在tabBar中。