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>