这里呈现出源码，查看一下结果。看一下json格式数据和xml格式数据的使用，还有就是更换数据后树的数据显示正常。
[quote]
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
initialize="initTree()"
>
<mx:Script>
<![CDATA[
import mx.controls.Alert;
[Bindable]
public var open:Object = new Object();
[Bindable]

public var refreshData:Boolean = false;
[Bindable]
public var switchObj:Object = new Object();
[Bindable]

public var firstObj:Object = new Object();
[Bindable]

public var firstObj1:Object = new Object();
[Bindable]

public var firstObj2:Object = new Object();
[Bindable]

public var provider:String = "firstObj";

private function initTree():void

{

firstObj = new Object();
firstObj.label = "Foods";
firstObj.children = new Array();
firstObj1.label = "Fruits";
firstObj1.children = new Array();
firstObj2.label = "Oranges";
firstObj1.children[0] = firstObj2;
firstObj.children[0] = firstObj1;
switchObj = [
{label:'root1',children:[{label:"firstChilden"},{label:"secondChild"}]}
,
{label:'root2',children:[{label:"firstChilden"},{label:"secondChild"}]}
];
}

public function changeProvider():void
{
open = SampleTree.openItems;
refreshData = true;
if (provider == "firstObj")

{
SampleTree.labelField="label";
provider = "switchObj";
SampleTree.dataProvider = switchObj;
}
else if (provider == "switchObj")
{
provider = "xmlObj";
SampleTree.labelField="@label";
SampleTree.dataProvider = treeData;
}
else if (provider == "xmlObj")
{
provider = "firstObj";
SampleTree.labelField="label";
SampleTree.dataProvider = firstObj;
}
}

public function renderTree():void{
if(refreshData){

// Refresh all rows on next update.
SampleTree.invalidateList();
refreshData = false;
SampleTree.openItems = open;
// Validate and update the properties and layout
// of this object and redraw it, if necessary.
SampleTree.validateNow();
}

}
]]>
</mx:Script>
<mx:XMLList id="treeData">
<node label="Mail Box">
<node label="Inbox">
<node label="Marketing"/>
<node label="Product Management"/>
<node label="Personal"/>
</node>
<node label="Outbox">
<node label="Professional"/>
<node label="Personal"/>
</node>
<node label="Spam"/>
<node label="Sent"/>
</node>
</mx:XMLList>
<mx:Tree id="SampleTree" render="renderTree()" showRoot="true" width="250" dataProvider="{firstObj}" labelField="label" />

<mx:Button label="Change Data Provider" click="changeProvider()"/>
</mx:Application>


[/quote]