flex只读属性Bindable

flex中,属性上标记Bindable,在属性变化时能进行数据绑定.
但是在只读的属性上加这标记,则不会起作用.
比如这个页面

<?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:Script>
		<![CDATA[
			private var bar1:int;
			
			private var bar2:int;
			
			private var bar3:int;
			
			[Bindable]
			public function get total():int{
				return bar1+bar2+bar3;
			}
			
			public function crap():void{
				bar1=5;
				bar2=10;
				bar3=1;
				
			}
		]]>
	</fx:Script>	
	<s:layout>
		<s:HorizontalLayout/>
	</s:layout>
	
	<s:Label text="{total}"/>
	
	<s:Button click="crap();"/>
	
</s:Application>

会提示
只读 getter 上的 [Bindable] 没有必要，因此将会被忽略

因此需要

			[Bindable(event="totalChanged")]
			public function get total():int{
				return bar1+bar2+bar3;
			}
			
			public function crap():void{
				bar1=5;
				bar2=10;
				bar3=1;
			this.dispatchEvent(newEvent("totalChanged",true,true));
			}

这样就能正常工作了.