FLEX例子之弹出按钮(PopUpButton)

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="top"
    horizontalAlign="center" backgroundGradientColors="[0x000000,0x323232]" paddingTop="0" viewSourceURL="srcview/index.html">
    <!--这个例子实现的是弹出式下拉菜单,但是这个PopUpButton不同于ComboBox,PopUpButton 控件可将灵活的弹出式控件接口添加到 Button 控件。
    它包含一个主按钮和一个辅助按钮，后者称为弹出按钮，用于用户单击此弹出按钮时弹出任何 UIComponent 对象。 
PopUpButton 控件的表面可包含一个文本标签、一个图标，或者两者都包含。当用户单击 PopUpButton 控件的主要部分时，此控件将调度 click 事件。
PopUpButton 控件的一个常见用法是，使弹出式按钮打开可更改主按钮的函数和标签的 List 控件或 Menu 控件。-->
    <mx:Script>
        <![CDATA[
 
            import mx.controls.*;
            import mx.events.*;
            import mx.controls.Alert;
 
            private var myMenu:Menu;
 
            // Initialize the Menu control, and specify it as the pop up object
            // of the PopUpButton control. 
            private function initMenu():void {
                myMenu = new Menu();
                var dp:Object = [{label: "New Folder"}, {label: "Sent Items"}, {label: "Inbox"}];    //定义数组    
                myMenu.dataProvider = dp;//赋值引用
                myMenu.selectedIndex = 0;       
                myMenu.addEventListener("itemClick", itemClickHandler);//添加监听
                popB.popUp = myMenu;
                popB.label = "Put in: " + myMenu.dataProvider[myMenu.selectedIndex].label;
            }
 
            // Define the event listener for the Menu control's itemClick event. 
            private function itemClickHandler(event:MenuEvent):void {
                var label:String = event.item.label;        
                popTypeB.text=String("Moved to " + label);
                popB.label = "Put in: " + label;
                popB.close();
                myMenu.selectedIndex = event.index;
            }
 
        ]]>
    </mx:Script>
 
    <mx:Panel title="PopUpButton Control" layout="vertical" color="0xffffff" borderAlpha="0.15"
         paddingTop="10" paddingRight="10" paddingBottom="10" paddingLeft="10" horizontalAlign="center">
 
         <mx:Label width="100%" color="0x323232"
            text="Button label contains the name of the last selected menu item." />
        <mx:PopUpButton id="popB" label="Edit" creationComplete="initMenu();" width="140" color="0x323232" click="{Alert.show('Action: ' + popB.label);}" />
 
        <mx:Spacer height="65" />//这个查看手册说是分配空间用的,可是我没有加这个东西的时候也是可以有空间被定位的
        <mx:TextInput id="popTypeB" color="0x323232" text="...waiting" />
 
    </mx:Panel>
</mx:Application>