格式化ComboBox控件的滚动条提示内容.

ComboBox控件的dropdown属性中的scrollTipFunction属性.
示例：

代码：

<? xml version="1.0" encoding="utf-8" ?>
<!--  http://blog.flexexamples.com/2008/07/01/formatting-scroll-tips-on-a-combobox-control-in-flex/  -->
< mx:Application  xmlns:mx ="http://www.adobe.com/2006/mxml"
        layout ="vertical"
        verticalAlign ="top"
        backgroundColor ="white" >

     < mx:Script >
         <![CDATA[
            import mx.events.DropdownEvent;

            private function comboBox_open(evt:DropdownEvent):void {
                comboBox.dropdown.showScrollTips = checkBox.selected;
                comboBox.dropdown.scrollTipFunction = comboBox_dropdown_scrollTipFunc;
            }

            private function comboBox_dropdown_scrollTipFunc(dir:String, pos:uint):String {
                return pos + " of " + comboBox.dropdown.maxVerticalScrollPosition;
            }
         ]]>
     </ mx:Script >

     < mx:Array  id ="arr" >
         < mx:Object  label ="One"   />
         < mx:Object  label ="Two"   />
         < mx:Object  label ="Three"   />
         < mx:Object  label ="Four"   />
         < mx:Object  label ="Five"   />
         < mx:Object  label ="Six"   />
         < mx:Object  label ="Seven"   />
         < mx:Object  label ="Eight"   />
         < mx:Object  label ="Nine"   />
         < mx:Object  label ="Ten"   />
     </ mx:Array >

     < mx:ApplicationControlBar  dock ="true" >
         < mx:Form  styleName ="plain" >
             < mx:FormItem  label ="showScrollTips:" >
                 < mx:CheckBox  id ="checkBox"
                        selected ="true"   />
             </ mx:FormItem >
         </ mx:Form >
     </ mx:ApplicationControlBar >

     < mx:ComboBox  id ="comboBox"
            dataProvider =" {arr} "
            open ="comboBox_open(event);"   />

</ mx:Application >