top,bottom,left,right,horizontalCenter和verticalCenter样式

verticalCenter=“0” 表示垂直居中，horizontalCenter=0表示水平居中

<?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>
 <s:BorderContainer horizontalCenter="0" verticalCenter="0" backgroundColor="#000000" backgroundAlpha="0.3" borderStyle="solid" borderColor="#000000" alpha="0.5" width="500" height="300">
  <mx:Text text="Top Left" left="10" top="10" />
  <mx:Text text="Bottom Left" left="10" bottom="10" />
  <mx:Text text="Bottom Center" bottom="10" horizontalCenter="0" />
  <mx:Text text="Center" horizontalCenter="0" verticalCenter="0" />
  <mx:Text text="Bottom Right" right="10" bottom="10" />
  <mx:Text text="Center Right" verticalCenter="0" right="10" />
  <mx:Text text="Center Left " left="10" verticalCenter="0" />
  <mx:Text text="Top Center" horizontalCenter="0" top="10" />
  <mx:Text text="Top Right" right="10" top="10" />
 </s:BorderContainer>
</s:Application>

来源：http://zw7534313.iteye.com/blog/848901