设置dropDownList没有水平、垂直滚动条

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2010/02/06/setting-the-horizontal-scroll-policy-on-a-spark-dropdownlist-control-in-flex-4/ -->
<s:Application name="Spark_DropDownList_scroller_horizontalScrollPolicy_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009" 
        xmlns:s="library://ns.adobe.com/flex/spark" 
        xmlns:mx="library://ns.adobe.com/flex/mx">
 
    <fx:Script>
        <![CDATA[
            import mx.core.ScrollPolicy;
        ]]>
    </fx:Script>
 
    <s:DropDownList id="ddl"
            width="100"
            horizontalCenter="0" top="20"
            open="ddl.scroller.setStyle('horizontalScrollPolicy', ScrollPolicy.OFF);">
        <s:dataProvider>
            <s:ArrayList source="[Accordion,ApplicationControlBar,Alert,Box,Button,ButtonBar,Canvas,ColorPicker]" />
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

如果要设置没有垂直滚动条： open="ddl.scroller.setStyle('verticalScrollPolicy', ScrollPolicy.OFF);"