Flex List行背景色

 过去在对DataGrid设置行背景色时，感觉还是挺方便的，只要重写DataGrid的，如下
private var _rowColorFunction:Function;
public function set rowColorFunction(f:Function):void
{
this._rowColorFunction = f;
}
public function get rowColorFunction():Function
{
return this._rowColorFunction;
}
override protected function drawRowBackground(s:Sprite, rowIndex:int, y:Number, height:Number, color:uint, dataIndex:int):void
{
if (this.rowColorFunction != null) {
if (dataIndex < this.dataProvider.length) {
var item:Object = this.dataProvider.getItemAt(dataIndex);
color = this.rowColorFunction.call(this, item, color);
}
}
super.drawRowBackground(s, rowIndex, y, height, color, dataIndex);
}

如果你还是不是很明白可以参考我以前的博客http://blog.csdn.net/terryzero/archive/2009/10/12/4657277.aspx
今天我碰到个需求是要对List行变色，由于我想DataGrid和List都是继承与ListBase,都有 override protected function drawRowBackground(s:Sprite, rowIndex:int, y:Number, height:Number, color:uint, dataIndex:int):void
这个方法，所以我就想当然，照葫芦画瓢，也重写了这个方法，但经过调试怎么也调用不到这个方法。搞的我非常费解，难道这个方法没用的啊？网上查了好久，国内没啥这方面的好文章，突然一篇国外的文章启发了我。如下
All the listy components in Flex (List, Datagrid, Tree, etc.) have a protected method called drawRowBackground which is in charge of drawing the background for a given row. You typically use it to color a given row based on some facet of the data the row represents (e.g. red background for rows with a negative bank balance).
With DataGrid, it's easy to use, just subclass DataGrid and override the method, parameterized so you can pass in a function to compute the color for each row based on the row index/data/original color/etc. With List (and since ComboBox uses a