Tree 添加节点 XML提供数据源

<?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"         layout="vertical"         verticalAlign="middle"         backgroundColor="white" horizontalAlign="left">     <mx:Script>  <![CDATA[  [Bindable]  public var selectedNode:XML;    private function treeHandler(event:Event):void      {      selectedNode =Tree(event.target).selectedItem as XML;      }    ]]>  </mx:Script>      <mx:XMLList id="xmlDP">         <node>             <node label="one" >                 <node label="1" />                 <node label="2" />                 <node label="3" />                 <node label="4" />                 <node label="5" />             </node>             <node label="two" >                 <node label="6" />                 <node label="7" />                 <node label="8" />                 <node label="9" />                 <node label="10" />                 <node label="11" />             </node>             <node label="three" >                 <node label="12" />                 <node label="13" />                 <node label="14" />                 <node label="15" />             </node>             <node label="four" >                 <node label="Proin nulla." />                 <node label="16" />                 <node label="17" />             </node>             <node label="five"  />         </node>     </mx:XMLList>      <mx:HDividedBox width="100%" height="100%">   <mx:Tree id="tree"             dataProvider="{xmlDP}"             showRoot="false"             dragEnabled="true"             dropEnabled="true"             dragMoveEnabled="true"             width="30%"  labelField="@label"            rowCount="6"  height="100%"  change="treeHandler(event)"/>    <mx:TextArea height="100%" width="70%" text="Selected Item: {selectedNode.@label}"/>  </mx:HDividedBox>            </mx:Application>