Flex中如何利用itemDoubleClick事件在双击Tree节点时展开该节点项目的例子

<?xml version="1.0" encoding="utf-8"?> 
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
        layout="horizontal" 
        verticalAlign="middle" 
        backgroundColor="white" 
        creationComplete="init();"> 
  
    <mx:Script> 
        <![CDATA[ 
            import mx.events.ListEvent; 
  
            private function tree_itemDoubleClick(evt:ListEvent):void { 
                var node:XML = tree.selectedItem as XML; 
                var isOpen:Boolean = tree.isItemOpen(node); 
                tree.expandItem(node, !isOpen); 
            } 
        ]]> 
    </mx:Script> 
  
    <mx:XMLListCollection id="xmlListColl"> 
        <mx:source> 
            <mx:XMLList> 
                <node label="One"> 
                    <node label="One.1"> 
                        <node label="One.1.1"> 
                            <node label="One.1.1.1"> 
                                <node label="One.1.1.1.1" /> 
                            </node> 
                        </node> 
                    </node> 
                    <node label="One.2" /> 
                    <node label="One.3" /> 
                </node> 
                <node label="Two"> 
                    <node label="Two.1" /> 
                    <node label="Two.2" /> 
                    <node label="Two.3" /> 
                </node> 
                <node label="Three" /> 
            </mx:XMLList> 
        </mx:source> 
    </mx:XMLListCollection> 
  
    <mx:ApplicationControlBar dock="true"> 
        <mx:CheckBox id="checkBox" 
                label="doubleClickEnabled:" 
                labelPlacement="left" 
                selected="true" /> 
    </mx:ApplicationControlBar> 
  
    <mx:Tree id="tree" 
            dataProvider="{xmlListColl}" 
            labelField="@label" 
            width="250" 
            rowCount="6" 
            doubleClickEnabled="{checkBox.selected}" 
            itemDoubleClick="tree_itemDoubleClick(event);" 
            showScrollTips="true" /> 
  
</mx:Application>