<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/27/setting-the-horizontal-scrollbar-policy-on-a-datagrid-control-in-flex/ -->
<mx:Application name="DataGrid_horizontalScrollPolicy_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.events.ListEvent;
            import mx.core.ScrollPolicy;

            private function comboBox_change(evt:ListEvent):void {
                var value:String = comboBox.selectedItem.toString();
                dataGrid.horizontalScrollPolicy = value;
            }
        ]]>
    </mx:Script>

    <mx:XML id="xmlDP" source="data/dp.xml" />

    <mx:Array id="arr">
        <mx:String>{ScrollPolicy.AUTO}</mx:String>
        <mx:String>{ScrollPolicy.OFF}</mx:String>
        <mx:String>{ScrollPolicy.ON}</mx:String>
    </mx:Array>

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="verticalScrollPolicy:">
                <mx:ComboBox id="comboBox"
                        dataProvider="{arr}"
                        selectedIndex="1"
                        change="comboBox_change(event);" />
            </mx:FormItem>
        </mx:Form>
        <mx:Spacer width="100%" />
        <mx:Button label="Set dataProvider"
                click="dataGrid.dataProvider = xmlDP.row;" />
        <mx:Button label="Clear dataProvider"
                click="dataGrid.dataProvider = [];" />
    </mx:ApplicationControlBar>

    <mx:DataGrid id="dataGrid"
            horizontalScrollPolicy="off"
            width="100%"
            height="100%" />

</mx:Application>