Flex TextArea滚动到底部

<mx:Script>
    <![CDATA[
    
        this.textarea.addEventListener(FlexEvent.VALUE_COMMIT,onValueCommit);

        private function onValueCommit(event:FlexEvent):void{ 

　　　　this.textarea.validateNow(); 

            this.textarea.verticalScrollPosition=this.textarea.maxVerticalScrollPosition;
        }
    ]]>
</mx:Script>


<mx:TextArea left="2" right="2" top="2" bottom="28" fontSize="12" editable="false" id="textarea">
    <mx:htmlText>
        <![CDATA[<b><font color='#FF0000'>Welcome to Flexchat!</font></b>]]>
    </mx:htmlText>

</mx:TextArea>