CustomRowColorDataGrid in flex 3

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
  xmlns:s="library://ns.adobe.com/flex/spark"
  xmlns:mx="library://ns.adobe.com/flex/mx"
  minWidth="955"
  minHeight="600" xmlns:local="*"
   >
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>

<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable]
public var getPatList:ArrayCollection=new ArrayCollection([{id: "Select", value: "Select"}, {id: "Left", value: ""}, {id: 'Right', value: ''}]);


private function setSerialNo(obj:Object, column:int):String
{
var indx:int=getPatList.getItemIndex(obj) + 1;
return String(indx);
}
private function getRowBackgroundColor(item:Object, color:uint):uint{
if( item.value ){
return 0xDA81F5;
}
return color;

}
]]>
</fx:Script>
<local:CustomRowColorDataGrid id="contentAlertDataGrid"
  dataProvider="{getPatList}"
  width="100%"
  height="100%"
  rowHeight="27"
  verticalScrollPolicy="off"
  horizontalScrollPolicy="off"
  resizableColumns="true"
  rowColorFunction="getRowBackgroundColor">
<local:columns>
<mx:DataGridColumn headerText="SNo"
  width="80"
  labelFunction="setSerialNo"/>
<mx:DataGridColumn headerText="RegNo"
  width="80"
  dataField="regNo"/>
<mx:DataGridColumn headerText="DoctorNo"
  width="100"
  dataField="docNo"/>
</local:columns>
</local:CustomRowColorDataGrid>
</s:Application>

===================================================================

package  

{

import mx.controls.DataGrid;

import flash.display.Shape;

import mx.core.FlexShape;

import flash.display.Graphics;

import flash.display.Sprite;

import mx.rpc.events.AbstractEvent;

import mx.collections.ArrayCollection;

import flash.events.Event;

/**

* This is an extended version of the built-in Flex datagrid.

* This extended version has the correct override logic in it

* to draw the background color of the cells, based on the value of the

* data in the row.

**/

public class CustomRowColorDataGrid extends DataGrid

{

private var _rowColorFunction:Function;

public function CustomRowColorDataGrid()

{

super();

}

/**

* A user-defined function that will return the correct color of the

* row. Usually based on the row data.

*

* expected function signature:

* public function F(item:Object, defaultColor:uint):uint

**/

public function set rowColorFunction(f:Function):void

{

this._rowColorFunction = f;

}

public function get rowColorFunction():Function

{

return this._rowColorFunction;

}

// private var displayWidth:Number; // I wish this was protected, or internal so I didn't have to recalculate it myself.

// override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void

// {

// super.updateDisplayList(unscaledWidth, unscaledHeight);

// if (displayWidth != unscaledWidth - viewMetrics.right - viewMetrics.left)

// {

// displayWidth = unscaledWidth - viewMetrics.right - viewMetrics.left;

// }

// }

//

/**

*  Draws a row background

*  at the position and height specified using the

*  color specified.  This implementation creates a Shape as a

*  child of the input Sprite and fills it with the appropriate color.

*  This method also uses the <code>backgroundAlpha</code> style property

*  setting to determine the transparency of the background color.

*

*  @param s A Sprite that will contain a display object

*  that contains the graphics for that row.

*

*  @param rowIndex The row's index in the set of displayed rows.  The

*  header does not count, the top most visible row has a row index of 0.

*  This is used to keep track of the objects used for drawing

*  backgrounds so a particular row can re-use the same display object

*  even though the index of the item that row is rendering has changed.

*

*  @param y The suggested y position for the background

*

*  @param height The suggested height for the indicator

*

*  @param color The suggested color for the indicator

*

*  @param dataIndex The index of the item for that row in the

*  data provider.  This can be used to color the 10th item differently

*  for example.

*/

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 as ArrayCollection).length )

{

var item:Object = (this.dataProvider as ArrayCollection).getItemAt(dataIndex);

color = this.rowColorFunction.call(this, item, color);

}

}

super.drawRowBackground(s, rowIndex, y, height, color, dataIndex);

}

}

}