flex的datagrid动态改变某行颜色,List控件行交叉颜色

import flash.display.Sprite;
 
 import mx.collections.ArrayCollection;
 import mx.controls.DataGrid;
 
 public class SQDataGrid extends DataGrid

 {
  public function SQDataGrid()
  {
  }
  protected override  function drawRowBackground(s:Sprite, rowIndex:int, y:Number, height:Number, color:uint, dataIndex:int):void
  {
    if(dataProvider&&dataIndex < (dataProvider as ArrayCollection).length){

         代码判断出可以取dataProvider 的数据来判断要改变什么颜色

           var item:Object = (dataProvider as ArrayCollection).getItemAt(dataIndex);
          if( item[2] > item[9] ){color=0xFF0000;}
      }
   super.drawRowBackground(s,rowIndex,y,height,color,dataIndex);

         }
 }

<?xml version="1.0" encoding="utf-8"?> 
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
        layout="vertical" 
        verticalAlign="middle" 
        backgroundColor="white"> 
  
    <mx:ArrayCollection id="arrColl"> 
        <mx:source> 
            <mx:Array> 
                <mx:Object label="Row 1" /> 
                <mx:Object label="Row 2" /> 
                <mx:Object label="Row 3" /> 
                <mx:Object label="Row 4" /> 
                <mx:Object label="Row 5" /> 
                <mx:Object label="Row 6" /> 
                <mx:Object label="Row 7" /> 
                <mx:Object label="Row 8" /> 
            </mx:Array> 
        </mx:source> 
    </mx:ArrayCollection> 
  
    <mx:List id="list" 
            alternatingItemColors="[0xEEEEEE, 0xDFDFDF]" 
            dataProvider="{arrColl}" 
            rowCount="4" 
            width="200" /> 
  
</mx:Application>