关于Flex的DataGrid的应用拓展（四）
Flex的Datagrid在程序中得应用非常广泛，使用起来也非常的简单。但功能还是不够，大家还要自己去实现一些自己的功能。比如排序，它只支持字符串排序，而面向日期或者时间的排序他就无能为力了。下面介绍如何实现数字和日期的自动排序。
1）通过实现DatagridColumn的继承，添加排序方法。

package{    import mx.controls.dataGridClasses.DataGridColumn;    import mx.utils.ObjectUtil;        public class SystemSortDatagridColumn extends DataGridColumn    {        public function SystemSortDatagridColumn(columnName:String=null)        {            super(columnName);            if(this.sortCompareFunction!=null){                this.sortCompareFunction=customSortColumn(this.dataField);            }        }                                public static function customSortColumn(sortField:String):Function{                return function(item1:Object, item2:Object):int{                    if(item1 is Number && item2 is Number)                    {                        return ObjectUtil.numericCompare(item1 as Number,item2 as Number);                    }else if(item1 is Date && item2 is Date){                        return ObjectUtil.dateCompare(item1 as Date,item2 as Date);                    }else{                       return  ObjectUtil.compare(item1 as String,item2 as String);                    }                                   }        }    }}

<?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" creationComplete="application1_creationCompleteHandler(event)" xmlns:local="*">    <fx:Declarations>        <!-- 将非可视元素（例如服务、值对象）放在此处 -->    </fx:Declarations>    <fx:Script>        <![CDATA[            import mx.collections.ArrayCollection;            import mx.collections.ArrayList;            import mx.events.FlexEvent;                        [Bindable]         public   var ac:ArrayCollection=new ArrayCollection();                        protected function application1_creationCompleteHandler(event:FlexEvent):void            {                ac.addItem({"name":"fu1" ,"age":21,"date":new Date()});                ac.addItem({"name":"fu2" ,"age":1});                ac.addItem({"name":"fu2" ,"age":111});                ac.addItem({"name":"fu3" ,"age":"fu"});                ac.addItem({"name":"fu4" ,"age":"fu1"});            }                    ]]>    </fx:Script>    <mx:DataGrid dataProvider="{ac}">        <mx:columns>            <local:SystemSortDatagridColumn headerText="Name" dataField="name" />            <local:SystemSortDatagridColumn headerText="Age" dataField="age" />        </mx:columns>    </mx:DataGrid>    </s:Application>