DataGrid中添加一列从1开始的序列，不随其它列的排序而发生混乱

给DataGrid或者表格的第一列加上行序列号，以此给用户一个提示当前数据所在的行号，就类似于Excel的左边列。Flex的DataGrid并没有自动提供这样的属性。那么如何解决这个问题呢，方法有很多种，一种直接简单的办法是用labelFunction和dataProvider数据源的获取当前索引号方法可以解决。
效果如图：


<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical">    
<mx:Script>
<![CDATA[
      import mx.events.FlexEvent;
      import mx.events.ScrollEvent;
      import mx.controls.dataGridClasses.DataGridColumn;
      import mx.collections.XMLListCollection;
      import mx.collections.ArrayCollection;
      private var xml:XML = <root>
            <vo region='southwest1' name='name1' id='id1' actual='111' estimate='1111'/>
            <vo region='southwest2' name='name2' id='id2' actual='222' estimate='2222'/>
            <vo region='southwest3' name='name3' id='id3' actual='333' estimate='3333'/>
            <vo region='southwest4' name='name4' id='id4' actual='444' estimate='4444'/>
            <vo region='southwest5' name='name5' id='id5' actual='555' estimate='5555'/>
            <vo region='southwest6' name='name6' id='id6' actual='666' estimate='6666'/>
            <vo region='southwest7' name='name7' id='id7' actual='777' estimate='7777'/>
            <vo region='southwest8' name='name8' id='id8' actual='888' estimate='8888'/>
            <vo region='southwest9' name='name9' id='id9' actual='999' estimate='9999'/>
            <vo region='southwest' name='name10' id='id10' actual='111' estimate='3333'/>
            <vo region='southwest' name='name11' id='id11' actual='111' estimate='3333'/>
            </root>;
      [Bindable]
      private var dpFlat:XMLListCollection = new XMLListCollection(xml.vo);
    
      private function LabFunc(item:Object, column:DataGridColumn):String
      {
            return ((dpFlat.getItemIndex(item)+1).toString());
      }
]]>
</mx:Script>
      <mx:DataGrid id="myADG" dataProvider="{dpFlat}" horizontalScrollPolicy="auto"
      width="100%" height="100%" minWidth="500">          
      <mx:columns>
           <mx:DataGridColumn labelFunction="LabFunc" width="30" minWidth="10" sortable="false" headerText="NO." resizable="false"/>[color=red][/color]
            <mx:DataGridColumn dataField="@region" headerText="Region" />               
            <mx:DataGridColumn dataField="@name" headerText="Name"/>
            <mx:DataGridColumn dataField="@id" headerText="Id"/>
            <mx:DataGridColumn dataField="@actual" headerText="Actual"/>
            <mx:DataGridColumn dataField="@estimate" headerText="Estimate"/>                              
      </mx:columns>
</mx:DataGrid>        
</mx:Application>