Flex图片加载失败和遮罩效果处理实例

<?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" minWidth="955" minHeight="600">
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
	<fx:Script>
		<![CDATA[
			[Embed(source='assets/default.gif')]
			public var defaultImg:Class;
		]]>
	</fx:Script>
	<s:Group horizontalCenter="0" verticalCenter="0">
		<s:Group depth="99" x="-22" y="-35" width="120" height="120">
			<s:Image id="doctorAvatar" source="http://blog.minidx.com/images/2.jpg" width="110" height="110" horizontalCenter="0" verticalCenter="0" 
					 mask="{cornerRadiusMask}" scaleMode="letterbox"  ioError="doctorAvatar.source=defaultImg;" />
			<s:BorderContainer id="cornerRadiusMask" width="100%" height="100%" backgroundColor="0xffffff" cornerRadius="90" />
			<s:BitmapImage source="@Embed('assets/bg.png')" />
		</s:Group>
	</s:Group>
</s:Application>