突然应对一个问题，DataGrid的dataProvider数据是可变的，但DataGrid的排序方式是轮循的，因此有些时候需要总是升序或降序，所以加上一个参数always，并在方法中进行改进，代码如下：
<?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">
<s:layout>
<s:VerticalLayout />
</s:layout>
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
import mx.collections.Sort;
import mx.collections.SortField;
import mx.events.DataGridEvent;
private const _arr:Array = [
{"str": "B", "num": 34},
{"str": "A", "num": 256},
{"str": "D", "num": 97},
{"str": "C", "num": 18},
{"str": "E", "num": 0}
];
private function onClick(columnIndex:int = -1,
sortDescending:Boolean = true, always:Boolean = true):void{
var _column:DataGridColumn = grid.columns[columnIndex];
_column.sortDescending = sortDescending;
//==========
if(always){
var _sort:Sort =
(grid.dataProvider as ArrayCollection || {}).sort;
if(_sort){
var _fields:Array = _sort.fields;
if(_fields){
(_fields[0] as SortField).descending =
!sortDescending;
}
}
}
//==========
grid.dispatchEvent(new DataGridEvent(
DataGridEvent.HEADER_RELEASE, false, false, columnIndex));
}
// private function onClick(columnIndex:int = -1,
// sortDescending:Boolean = true):void{
// var _column:DataGridColumn = grid.columns[columnIndex];
// _column.sortDescending = sortDescending;
// grid.dispatchEvent(new DataGridEvent(
// DataGridEvent.HEADER_RELEASE, false, false, columnIndex));
// }
]]>
</fx:Script>
<mx:DataGrid id="grid" dataProvider="{_arr}" width="320" height="240">
<mx:columns>
<mx:DataGridColumn dataField="str" headerText="String" />
<mx:DataGridColumn dataField="num" headerText="Number" />
</mx:columns>
</mx:DataGrid>
<s:Button label="String排序" width="100" click="onClick(0, false)" />
<s:Button label="Number排序" width="100" click="onClick(1)" />
</s:Application>
视图：
