flex4 自定义右键菜单

<?xml version="1.0" encoding="utf-8"?>  
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"  
        layout="vertical"  
        verticalAlign="middle"  
        backgroundColor="white"  
        creationComplete="init()">  
   
    <mx:Script>  
        <![CDATA[ 
            import mx.controls.Alert; 
  
            [Bindable] 
            private var cm:ContextMenu; 
  
            private var alert:Alert; 
  
            private function init():void { 
                var cmi:ContextMenuItem = new ContextMenuItem("菜单项", true); 
                cmi.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, contextMenuItem_menuItemSelect); 
                var cmi1:ContextMenuItem = new ContextMenuItem("菜单项1", false); 
                cmi1.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, contextMenuItem_menuItemSelect1); 
                 
                cm = new ContextMenu(); 
                cm.hideBuiltInItems(); 
                cm.customItems = [cmi,cmi1]; 
                cm.addEventListener(ContextMenuEvent.MENU_SELECT, contextMenu_menuSelect); 
            } 
  
            private function contextMenu_menuSelect(evt:ContextMenuEvent):void { 
                dataGrid.selectedIndex = lastRollOverIndex; 
            } 
  
            private function contextMenuItem_menuItemSelect(evt:ContextMenuEvent):void { 
                var obj:Object = dataGrid.selectedItem; 
                alert = Alert.show("Property A: " + obj.@propertyA + "\n" + "Property B: " + obj.@propertyB, obj.@label, Alert.OK); 
            } 
            private function contextMenuItem_menuItemSelect1(evt:ContextMenuEvent):void { 
                var obj:Object = dataGrid.selectedItem; 
                alert = Alert.show("Property A: " + obj.@propertyA + "\n" + "Property B: " + obj.@propertyB, obj.@label, Alert.OK); 
            } 
        ]]>  
    </mx:Script>  
   
    <mx:XML id="itemsXML">  
        <items>  
            <item label="Item 1" data="i001" propertyA="Item 1.A" propertyB="Item 1.B" />  
            <item label="Item 2" data="i002" propertyA="Item 2.A" propertyB="Item 2.B" />  
            <item label="Item 3" data="i003" propertyA="Item 3.A" propertyB="Item 3.B" />  
            <item label="Item 4" data="i004" propertyA="Item 4.A" propertyB="Item 4.B" />  
            <item label="Item 5" data="i005" propertyA="Item 5.A" propertyB="Item 5.B" />  
            <item label="Item 6" data="i006" propertyA="Item 6.A" propertyB="Item 6.B" />  
            <item label="Item 7" data="i007" propertyA="Item 7.A" propertyB="Item 7.B" />  
            <item label="Item 8" data="i008" propertyA="Item 8.A" propertyB="Item 8.B" />  
        </items>  
    </mx:XML>  
   
    <mx:Number id="lastRollOverIndex" />  
   
    <mx:DataGrid id="dataGrid"  
            width="400"  
            dataProvider="{itemsXML.item}"  
             contextMenu="{cm}"  
             itemRollOver="lastRollOverIndex = event.rowIndex">  
        <mx:columns>  
            <mx:DataGridColumn id="labelCol"  
                    dataField="@label"  
                    headerText="Label:" />  
   
            <mx:DataGridColumn id="propACol"  
                    dataField="@propertyA"  
                    headerText="Property A:" />  
   
            <mx:DataGridColumn id="propBCol"  
                    dataField="@propertyB"  
                    headerText="Property B:" />  
        </mx:columns>  
    </mx:DataGrid>  
   
    <mx:Label text="{dataGrid.selectedItem.@label}" />  
   
</mx:Application>