flex4 Tree默认打开指定项并选中指定节点

<mx:Tree id="tree" change="tree_changeHandler(event)" dataProvider="{zxljd}" width="300" height="100%" labelField="@name" showRoot="false" creationComplete="tree1_creationCompleteHandler(event)">
		
	</mx:Tree>
	<fx:Script>
		<![CDATA[
			[Bindable]
			private var zxljd:XML = getZxljd();//动态生成xml作为tree数据源
			public  function getZxljd():XML{
				var treexml:XML = new XML(<tree/>);
				for(var i:int=(new Date().fullYear-7); i<=(new Date().fullYear); i++)
				{
					var yearxml:XML = new XML(<year/>);
					yearxml.@name = i + "年";
					
					for(var j:int=1; j<13; j++)
					{
						var monthxml:XML = new XML(<month/>);
						monthxml.@name = j + "月";
						yearxml.appendChild(monthxml);
					}
					treexml.appendChild(yearxml);
				}
				return treexml;
			}
			
			
			protected function tree1_creationCompleteHandler(event:FlexEvent):void
			{
				//打开2006年这个节点(不要用openItems方法,否则会影响下面设置默认选中效果)
				tree.expandChildrenOf(zxljd.year.(@name == "2006年")[0],true);
				//设置默认选中五月
				tree.selectedItem = (zxljd.year.(@name == "2006年").month.(@name == "5月")[0]) as XML;
			}
			
			
			protected function tree_changeHandler(event:ListEvent):void
			{
				trace(tree.selectedItem.toXMLString());
			}
		]]>
	</fx:Script>