对一个集合排序，经常用到类似下面的代码片段：
ArrayCollection(this.dataProvider).addEventListener(CollectionEvent.COLLECTION_CHANGE,onRefresh); var sort:Sort = new Sort(); sort.fields = [new SortField(this._sortField,false,false,Array.NUMERIC)]; ArrayCollection(this.dataProvider).sort = sort; _debugString+=(new Date().time+" sortStartTime")+"\n"; trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"AA"); ArrayCollection(this.dataProvider).refresh(); trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"BB");
private function onRefresh(e:CollectionEvent):void
{
switch(e.kind)
{
case "refresh":
trace("refresh finished!");
break;
}
}
}
一直以为集合调用refresh()方法后才开始排序，直到ArrayCollection发出CollectionEvent（kind="refresh"）事
件后，排序才完成。如是在CollectionEvent事件处理函数中来处理排序后的集合数据...其实这是错误的！！
其实，在执行refresh()时，是先对数据进行排序后更新视图。至于排序什么时候完成的，没有通知。
当CollectionEvent（kind="refresh"）事件发送时，排序肯定完成，且视图也更新完成，它是用来
告诉你视图更新完成而非排序完成。所以上面的输出
trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"AA");
是原始集合的第一项，未排序的第一项
trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"BB");
是排序后集合的第一项，也是视图更新后视图中的第一项如：list组件的第一项等。
上面的三个trace语句执行顺序应该是：
1。trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"AA");
2。trace("refresh finished!");
3。trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"BB");
不管你的排序集合有多少数据，只要执行排序操作不超过编译器默认时间限制15秒，它都会按照上面的顺序执行。
也许你会认为当排序的数据很多的时候如：1000000时，排序时间会很长，在1执行后会执行3，排序完成执行2？但这个是错误的！
下面有个测试的例子：
MyList.as
package myComponent
{
import mx.collections.ArrayCollection;
import mx.collections.Sort;
import mx.collections.SortField;
import mx.controls.List;
import mx.events.CollectionEvent;
public class MyList extends List
{
private var _myData:ArrayCollection;
private var _sortField:String;
private var _count:int;
private var _isSort:Boolean;
private var _timeStart:Number;
private var _maxWidth:int;
private var _debugString:String;
private var _isMeasure:Boolean;
private var _isChange:Boolean;
public function MyList()
{
_debugString="";
}
override public function set dataProvider(value:Object):void
{
super.dataProvider = value;
this._isChange=true;
ArrayCollection(this.dataProvider).addEventListener(CollectionEvent.COLLECTION_CHANGE,onRefresh);
}
override protected function commitProperties():void
{
super.commitProperties();
if(this._isChange)
{
if(this.dataProvider is ArrayCollection)
{
if(this.dataProvider.length<=0)return;
var sort:Sort = new Sort();
sort.fields = [new SortField(this._sortField,false,false,Array.NUMERIC)];
ArrayCollection(this.dataProvider).sort = sort;
_debugString+=(new Date().time+" sortStartTime")+"\n";
trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"AA");
ArrayCollection(this.dataProvider).refresh();
trace(ArrayCollection(this.dataProvider).getItemAt(0).a,"BB");
_debugString+="be sorted!!\n";
_debugString+="====================";
_count++;
this._isSort=true;
}
this._isChange=false;
}
}
public function set sortField(value:String):void
{
this._sortField = value;
}
public function get sortField():String
{
return this._sortField;
}
override protected function measure():void
{
super.measure();
if(!this.dataProvider)return;
if(this.dataProvider.length<=0)return;
var n:int = this.dataProvider.length;
if(_isSort)
{
for(var i:int = 0;i<n;i++)
{
var len:int = this.dataProvider.getItemAt(i)[_sortField].toString().length;
if(len>_maxWidth)_maxWidth=len;
}
trace("Just One!!");
this.minWidth = _maxWidth*10;
this.measuredWidth = _maxWidth*10;
_isSort=false;
}
}
private function onRefresh(e:CollectionEvent):void
{
switch(e.kind)
{
case "refresh":
_debugString+=(new Date().time+" sortEndTime")+"\n";
break;
}
}
[Bindable]
public function get debugString():String
{
return this._debugString;
}
public function set debugString(value:String):void
{
}
}
}
主文件：
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:myComponent="myComponent.*" creationComplete="init()">
<mx:Script>
<![CDATA[
import mx.events.ListEvent;
import mx.events.ItemClickEvent;
import mx.collections.ArrayCollection;
[Embed(source='../.version',mimeType="application/octet-stream")]
private var ver:Class;
private function getRandomStr():String
{
var random:int = 1+Math.floor(Math.random()*(30));
var str:String = "";
for(var i:int = 0;i<random;i++)
{
str+=String.fromCharCode(97+Math.floor(Math.random()*(26)));
}
return str;
}
private function setDp(n:int):ArrayCollection
{
var dp:ArrayCollection = new ArrayCollection;
for(var i:int = 0;i<n;i++)
{
var o:Object = {};
o.a = getRandomStr();
o.b = Math.floor(Math.random()*1000)+1;
dp.addItem(o);
}
return dp;
}
private function init():void
{
VersionUtil.setRightMenu(ver,this,"TestApp Build@build R@release");
myList.dataProvider = setDp(1000);
ta.text = myList.debugString;
}
private function listClick(e:ListEvent):void
{
trace(myList.selectedItem.a);
}
private function sort():void
{
var n:int = int(numTi.text);
myList.dataProvider = setDp(n);
ta.text = myList.debugString;
}
]]>
</mx:Script>
<myComponent:MyList id="myList" labelField="a" sortField="a" x="379" y="10" height="607" itemClick="listClick(event)"/>
<mx:TextInput x="10" y="11" id="numTi" text="1000"/>
<mx:Button x="10" y="41" label="sort" id="btn" click="sort()"/>
<mx:TextArea id="ta" x="10" y="81" text="{myList.debugString}" height="467" width="361"/>
</mx:Application>
最终的测试：demo