<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/02/28/displaying-the-sort-arrow-in-a-flex-datagrid-control-without-having-to-click-a-column/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Script>
        <![CDATA[
            import mx.collections.Sort;
            import mx.collections.SortField;

            private function init():void {
                arrColl.sort = new Sort();
                arrColl.sort.fields = [new SortField("idx", false, true)];
                arrColl.refresh();
            }
        ]]>
    </mx:Script>

    <mx:ArrayCollection id="arrColl">
        <mx:source>
            <mx:Array>
                <mx:Object idx="1" c1="One.1" c2="One.2" />
                <mx:Object idx="2" c1="Two.1" c2="Two.2" />
                <mx:Object idx="3" c1="Three.1" c2="Three.2" />
                <mx:Object idx="4" c1="Four.1" c2="Four.2" />
                <mx:Object idx="5" c1="Five.1" c2="Five.2" />
                <mx:Object idx="6" c1="Six.1" c2="Six.2" />
                <mx:Object idx="7" c1="Seven.1" c2="Seven.2" />
                <mx:Object idx="8" c1="Eight.1" c2="Eight.2" />
                <mx:Object idx="9" c1="Nine.1" c2="Nine.2" />
                <mx:Object idx="10" c1="Ten.1" c2="Ten.2" />
                <mx:Object idx="11" c1="Eleven.1" c2="Eleven.2" />
                <mx:Object idx="12" c1="Twelve.1" c2="Twelve.2" />
                <mx:Object idx="13" c1="Thirteen.1" c2="Thirteen.2" />
            </mx:Array>
        </mx:source>
    </mx:ArrayCollection>

    <mx:DataGrid id="dataGrid"
            dataProvider="{arrColl}"
            creationComplete="init();">
        <mx:columns>
            <mx:DataGridColumn dataField="idx" />
            <mx:DataGridColumn dataField="c1" />
            <mx:DataGridColumn dataField="c2" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>