Flex Tree 如何在不选定节点的情况下进行添加（Demo）

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" width="800" height="500" creationComplete="init()" xmlns:ns1="aaa.*">
	<mx:Script>
		<![CDATA[
			import mx.events.TreeEvent;
			import mx.collections.ArrayCollection;
			private function handleItemClose(evt:TreeEvent):void 
			{
				tree1.expandChildrenOf(evt.item,false);
			}
			
			private function init():void {
				this.tree1.addEventListener(TreeEvent.ITEM_CLOSE,handleItemClose);
			}
			
			private function getAllChildLabel():void 
			{
				if(tree1.selectedItem) {
					var allChild:Array = [];
					var xml:XML = tree1.selectedItem as XML;
					this.getAllChild(allChild,xml);
					this.textArea1.text = allChild.join("n");
				}
			}
			private function getAllChild(allChild:Array,xml:XML):void 
			{
				allChild.push(xml.@label);
				if(xml.children().length()>0) {
					for each(var node:XML in xml.children())
					arguments.callee(allChild,node);
				}
			}
			
			private function getAllParentLabel():void
			{
				if(tree1.selectedItem) {
					var allParent:Array = [];
					var xml:XML = tree1.selectedItem as XML;
					this.getAllParent(allParent,xml);
					this.textArea1.text = allParent.join("n");
				}
			}
			
			private function getAllParent(allParent:Array,xml:XML):void 
			{
				allParent.push(xml.@label);
				if(xml.parent()) {
					arguments.callee(allParent,xml.parent());
				}
			}
			private function getTreeLabel():void
			{
				if(tree1.selectedIndex = 1)
				{
		 var s:XML =		tree1.selectedItem  as XML;
		var newNode:XML =<Pfolder/>;
		newNode.@label="自定义333333";
		// 添加节点
	
		if (s.length() > 0)
		{
			s[0].appendChild(newNode);
		}
		
				}
				
			}
			
		]]>
	</mx:Script>
	<mx:Tree id="tree1" labelField="@label" showRoot="true" width="300" height="300">
		<mx:XMLListCollection id="MailBox">
			<mx:XMLList>
				<folder label="Mail">
					<folder label="INBOX"/>
					<folder label="Personal Folder">
						<Pfolder label="Business" />
						<Pfolder label="Demo" /> 
						<Pfolder label="Personal" isBranch="true" /> 
						<Pfolder label="Saved Mail" /> 
					</folder>
					<folder label="Sent" />
					<folder label="Trash" />
				</folder>
				<folder label="自定义视图">
					<folder label="自定义视图">
						<Pfolder label="节点1" />
						<Pfolder label="节点2" /> 
					</folder>
				</folder>
			</mx:XMLList>
		</mx:XMLListCollection>
	</mx:Tree>
	<mx:Button id="button1" x="201" y="308" label="得到选择节点下的所有子节点label值" click="getAllChildLabel()" />
	<mx:Button id="button2" x="201" y="338" label="得到选择节点的所有父节点label值" click="getAllParentLabel()" />
	<mx:Button id="button3" x="201" y="368" label="得到树所有及诶单label值" click="getTreeLabel()" />
	<mx:TextArea id="textArea1" x="317" y="2" width="276" height="298"/>
	
</mx:Application>