flex tree 添加右键菜单

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" fontSize="12">
<mx:Script>
<!--[CDATA[
import mx.controls.Alert;

public var newBuildMenuItem:ContextMenuItem;//菜单项变量

private function init(): void//初始化函数
{
createTreeMenuItem();
tree.contextMenu = getTreeContxtMenu();
}
public function createTreeMenuItem(): void//菜单项创建函数，并添加菜单监听器
{
newBuildMenuItem = new ContextMenuItem("新建");
newBuildMenuItem.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, newBuildHandler2);
}

private function getTreeContxtMenu(): ContextMenu//将菜单项目添加到菜单中
{
var contextMenu: ContextMenu = new ContextMenu();
contextMenu.hideBuiltInItems();
contextMenu.customItems.push(newBuildMenuItem);
return contextMenu;
}
public function newBuildHandler2(event:Event):void//点击菜单执行函数
{
Alert.show("这是新建的菜单点击后执行的函数");
}
]]-->
</mx:Script>
<mx:Tree id="tree" x="31" y="10"  creationComplete="init()"></mx:Tree>

</mx:Application>