使ComboBox控件子选项的高度随内容自适应.

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

代码：

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/07/04/creating-a-variable-row-height-item-renderer-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 {
                evt.currentTarget.dropdown.variableRowHeight = true;
            }
        ]]>
    </mx:Script>

    <mx:Array id="arr">
        <mx:Object name="Baltimore Orioles" abbr="BAL" />
        <mx:Object name="Boston Red Sox" abbr="BOS" />
        <mx:Object name="Chicago White Sox" abbr="CWS" />
        <mx:Object name="Cleveland Indians" abbr="CLE" />
        <mx:Object name="Detroit Tigers" abbr="DET" />
        <mx:Object name="Kansas City Royals" abbr="KC" />
        <mx:Object name="Los Angeles Angels of Anaheim" abbr="LAA" />
        <mx:Object name="Minnesota Twins" abbr="MIN" />
        <mx:Object name="New York Yankees" abbr="NYY" />
        <mx:Object name="Oakland Athletics" abbr="OAK" />
        <mx:Object name="Seattle Mariners" abbr="SEA" />
        <mx:Object name="Tampa Bay Devil Rays" abbr="TB" />
        <mx:Object name="Texas Rangers" abbr="TEX" />
        <mx:Object name="Toronto Blue Jays" abbr="TOR" />
    </mx:Array>

    <mx:ComboBox id="comboBox"
            dataProvider="{arr}"
            width="140"
            labelField="name"
            open="comboBox_open(event);">
        <mx:itemRenderer>
            <mx:Component>
                <mx:Text selectable="false"
                        toolTip="{data.name} ({data.abbr})" />
            </mx:Component>
        </mx:itemRenderer>
    </mx:ComboBox>

</mx:Application>