让ButtonBar显示ViewStack自定义的icon

<?xml version="1.0" encoding="utf-8"?>
<s:Group 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:view="ddkj.eb.cms.view.*"
width="400" height="300">
<s:layout>
<s:BasicLayout/>
</s:layout>
<fx:Declarations>
<!-- 将非可视元素（例如服务、值对象）放在此处 -->
</fx:Declarations>
<s:BorderContainer top="-1" right="-1" bottom="-1" left="-1" backgroundImage="@Embed(source='http://www.cnblogs.com/http://www.cnblogs.com/__assets/skin/default/header-bar.png')" backgroundImageFillMode="repeat">
<s:ButtonBar dataProvider="{this.viewStack1}" top="10" height="50" skinClass="skins.CustomButtonBarSkin" horizontalCenter="0"/>
<mx:HRule left="0" top="69" right="0" height="1"/>
<mx:ViewStack id="viewStack1" bottom="0" right="0" top="70" left="0" backgroundColor="#FFFFFF" backgroundAlpha="0.2">
<s:NavigatorContent width="100%" height="100%" label="列表" icon="@Embed(source='http://www.cnblogs.com/http://www.cnblogs.com/__assets/icon/main/36/list.png')">
<view:ArticleListView width="100%" height="100%"/>
</s:NavigatorContent>
<s:NavigatorContent width="100%" height="100%" label="修改" icon="@Embed(source='http://www.cnblogs.com/http://www.cnblogs.com/__assets/icon/main/36/modify.png')">
<view:ArticleModifyView width="100%" height="100%"/>
</s:NavigatorContent>
<s:NavigatorContent width="100%" height="100%" label="新增" icon="@Embed(source='http://www.cnblogs.com/http://www.cnblogs.com/__assets/icon/main/36/add.png')">
<view:ArticleAddView width="100%" height="100%"/>
</s:NavigatorContent>
</mx:ViewStack>
</s:BorderContainer>
</s:Group>

注意这一句skinClass="skins.CustomButtonBarSkin"
skins包下面的CustomButtonBarSkin

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/28/displaying-icons-in-a-spark-buttonbar-control-in-flex-4/ -->
<s:Skin name="CustomButtonBarSkin"
xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
alpha.disabled="0.5">
<!-- states -->
<s:states>
<s:State name="normal" />
<s:State name="disabled" />
</s:states>

<fx:Metadata>
<![CDATA[
[HostComponent("spark.components.ButtonBar")]
]]>
</fx:Metadata>

<fx:Declarations>
<fx:Component id="middleButton">
<s:ButtonBarButton skinClass="skins.CustomButtonBarButtonSkin" />
</fx:Component>
</fx:Declarations>

<s:DataGroup id="dataGroup" width="100%" height="100%">
<s:layout>
<s:ButtonBarHorizontalLayout gap="-1"/>
</s:layout>
</s:DataGroup>

</s:Skin>

skins包下面的CustomButtonBarButtonSkin

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/28/displaying-icons-in-a-spark-buttonbar-control-in-flex-4/ -->
<s:SparkSkin name="CustomButtonBarButtonSkin"
xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
minWidth="21" minHeight="21"
alpha.disabledStates="0.5">
<!-- states -->
<s:states>
<s:State name="up" />
<s:State name="over" stateGroups="overStates" />
<s:State name="down" stateGroups="downStates" />
<s:State name="disabled" stateGroups="disabledStates" />
<s:State name="upAndSelected" stateGroups="selectedStates, selectedUpStates" />
<s:State name="overAndSelected" stateGroups="overStates, selectedStates" />
<s:State name="downAndSelected" stateGroups="downStates, selectedStates" />
<s:State name="disabledAndSelected" stateGroups="selectedUpStates, disabledStates, selectedStates" />
</s:states>

<!-- host component -->
<fx:Metadata>
<![CDATA[
[HostComponent("spark.components.ButtonBarButton")]
]]>
</fx:Metadata>

<fx:Script>
<![CDATA[
import spark.components.ButtonBar;
import mx.events.FlexEvent;
import spark.components.ButtonBarButton;

protected function gr_creationComplete(evt:FlexEvent):void {
var dataObj:Object = hostComponent.data;
img.source = dataObj.icon;
hostComponent.toolTip = dataObj.label;
}

/* Define the skin elements that should not be colorized.
For toggle button, the graphics are colorized but the label is not. */
static private const exclusions:Array = [];

override public function get colorizeExclusions():Array {return exclusions;}
]]>
</fx:Script>

<!-- layer 1: shadow -->
<s:Rect left="0" right="0" bottom="-1" height="1">
<s:fill>
<s:SolidColor color="0x000000"
color.downStates="0xFFFFFF"
alpha="0.07"
alpha.downStates="0.5" />
</s:fill>
</s:Rect>

<!-- layer 2: fill -->
<s:Rect left="1" right="1" top="1" bottom="1">
<s:fill>
<s:LinearGradient rotation="90">
<s:GradientEntry color="0xFFFFFF"
color.selectedUpStates="0xBBBDBD"
color.overStates="0xBBBDBD"
color.downStates="0xAAAAAA"
alpha="0.85"
alpha.overAndSelected="1" />
<s:GradientEntry color="0xD8D8D8"
color.selectedUpStates="0x9FA0A1"
color.over="0x9FA0A1"
color.overAndSelected="0x8E8F90"
color.downStates="0x929496"
alpha="0.85"
alpha.overAndSelected="1" />
</s:LinearGradient>
</s:fill>
</s:Rect>

<!-- layer 3: fill lowlight -->
<s:Rect left="1" right="1" bottom="1" height="9">
<s:fill>
<s:LinearGradient rotation="90">
<s:GradientEntry color="0x000000" alpha="0.0099" />
<s:GradientEntry color="0x000000" alpha="0.0627" />
</s:LinearGradient>
</s:fill>
</s:Rect>

<!-- layer 4: fill highlight -->
<s:Rect left="1" right="1" top="1" height="9">
<s:fill>
<s:SolidColor color="0xFFFFFF"
alpha="0.33"
alpha.selectedUpStates="0.22"
alpha.overStates="0.22"
alpha.downStates="0.12" />
</s:fill>
</s:Rect>

<!-- layer 5: highlight stroke (all states except down) -->
<s:Rect left="1" right="1" top="1" bottom="1"
excludeFrom="downStates">
<s:stroke>
<s:LinearGradientStroke rotation="90" weight="1">
<s:GradientEntry color="0xFFFFFF"
alpha.overStates="0.22"
alpha.selectedUpStates="0.33" />
<s:GradientEntry color="0xD8D8D8"
alpha.overStates="0.22"
alpha.selectedUpStates="0.33" />
</s:LinearGradientStroke>
</s:stroke>
</s:Rect>

<!-- layer 6: highlight stroke (down state only) -->
<s:Rect left="1" top="1" bottom="1" width="1"
includeIn="downStates, selectedUpStates, overAndSelected">
<s:fill>
<s:SolidColor color="0x000000" alpha="0.07" />
</s:fill>
</s:Rect>
<s:Rect right="1" top="1" bottom="1" width="1"
includeIn="downStates, selectedUpStates, overAndSelected">
<s:fill>
<s:SolidColor color="0x000000" alpha="0.07" />
</s:fill>
</s:Rect>
<s:Rect left="1" top="1" right="1" height="1"
includeIn="downStates, selectedUpStates, overAndSelected">
<s:fill>
<s:SolidColor color="0x000000" alpha="0.25" />
</s:fill>
</s:Rect>
<s:Rect left="1" top="2" right="1" height="1"
includeIn="downStates, selectedUpStates, overAndSelected">
<s:fill>
<s:SolidColor color="0x000000" alpha="0.09" />
</s:fill>
</s:Rect>

<!-- layer 7: border - put on top of the fill so it doesn't disappear when scale is less than 1 -->
<s:Rect left="0" right="0" top="0" bottom="0"
width="69" height="20">
<s:stroke>
<s:LinearGradientStroke rotation="90" weight="1">
<s:GradientEntry color="0x000000"
alpha="0.5625"
alpha.down="0.6375"
alpha.selectedStates="0.6375" />
<s:GradientEntry color="0x000000"
alpha="0.75"
alpha.down="0.85"
alpha.selectedStates="0.85" />
</s:LinearGradientStroke>
</s:stroke>
</s:Rect>

<!-- layer 8: icon -->
<s:Graphic id="gr"
creationComplete="gr_creationComplete(event);"
horizontalCenter="0" verticalCenter="0">
<s:BitmapImage id="img" />
</s:Graphic>

</s:SparkSkin>

代码完毕