Lazy-loaded tree example

mx:application mx="http://www.adobe.com/2006/mxml" layout="absolute" creationcomplete="creationCompleteHandler()"

import mx.utils.ObjectProxy;
import mx.events.TreeEvent;
import mx.collections.ArrayCollection;
private var myEvent:TreeEvent;

[Bindable]
private var acSiteTreeList:ArrayCollection;

private function creationCompleteHandler():void {
var obj:Object;
acSiteTreeList = new ArrayCollection ();
for(var i:int = 0; i < 3; i++) {
obj= new Object();
obj["type"] = "something";
obj["children"] = new ArrayCollection();
//fetch is a property in the dataprovider to check if I have fetched the child nodes previously
obj["fetch"] = false;
obj["label"] = "name " + i.toString();
acSiteTreeList.addItem(obj);
}
}

private function setView(event:TreeEvent):void {
if(event.item.type == "something" && event.item.fetch == false) {
myEvent = event; //(myEvent is of type TreeEvent)
//update the dataprovider
var obj:ObjectProxy;
var item:Object;
var children:ArrayCollection;
for(var i:int = 0; i < acSiteTreeList.length; i++) {
obj= new ObjectProxy();
obj["type"] = "something";
//obj["children"] = new ArrayCollection(bloggersArray);
//fetch is a property in the dataprovider to check if I have fetched the child nodes previously
obj["fetch"] = false;
obj["label"] = "node " + i.toString();
item = myEvent.item;
children = item.children;
item.fetch = true;
children.addItem(obj);
acSiteTreeList.itemUpdated(item);
}
}
}

mx:canvas width="100%" height="100%"
mx:tree id="treeSiteList" dataprovider="{acSiteTreeList}" x="204" y="10" height="582" width="394" itemopen="setView(event)"
mx:Canvas
mx:Application