flex之下拉框值更改事件调用JavaScript函数

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
			   xmlns:s="library://ns.adobe.com/flex/spark" 
			   initialize="initApp()"
			   xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
	<s:layout>
		<s:BasicLayout/>
	</s:layout>

	<fx:Script>
		<![CDATA[
			import mx.collections.ArrayCollection;
			import mx.controls.Alert;
			
			import spark.events.IndexChangeEvent;  
			
			[Bindable]  
			private var datas:ArrayCollection = new ArrayCollection([{label:"选项1"},{label:"选项2"},{label:"选项3"},{label:"选项4"}]);  
			
			//第一步：在mxml应用程序启动后执行：把js可以调用的ActionScript 函数注册
			public function initApp():void 
			{   
				//把flexHelloWorld 函数注册成名为flexHelloWorld，可以供js调用
				ExternalInterface.addCallback("flexHelloWorld", flexHelloWorld);   
			}
			
			//供js调用的ActionScript函数，这里的param1，param2是从js传递回来的参数
			public function flexHelloWorld(param1:String, param2:String):void 
			{   
				Alert.show("param1: " + param1 + "; param2:" + param2);   
			}  
			
			protected function userName_changeHandler(event:TextOperationEvent):void
			{
				//flex调用JavaScript函数的方式：如下：第一个参数是JavaScript中的函数名称，第二个参数
				//是JavaScript函数中接受的参数
				ExternalInterface.call("javascriptFunction",userName.text);
			}
			
			protected function newItem_clickHandler(event:MouseEvent):void
			{
				var s:String = itemValue.text;
				datas.addItem(s);
				items.selectedIndex = datas.length;
				itemValue.text="";
			}
			
			protected function delItem_clickHandler(event:MouseEvent):void
			{
				datas.removeItemAt(items.selectedIndex);
				items.selectedIndex=0;
			}

			//下拉框值更改事件
			protected function items_changeHandler(event:IndexChangeEvent):void
			{
				//调用JavaScript中的函数
				ExternalInterface.call("javascriptFunction",userName.text);
				Alert.show(event.currentTarget.toString());
			}

		]]>
	</fx:Script>

	<fx:Script>
		<![CDATA[
			import spark.events.TextOperationEvent;
		]]>
	</fx:Script>
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
	
	<s:TextInput id="userName" change="userName_changeHandler(event)" />
	<s:Panel width="250" height="200" title="下拉框案例" x="0" y="60">
		<s:TextInput id="itemValue" x="10" y="75" width="150"/>
		<s:Button id="newItem" x="168" y="75" label="新建项" click="newItem_clickHandler(event)"/>
		<s:ComboBox id="items" x="10" y="34" width="228" dataProvider="{datas}" selectedIndex="0" change="items_changeHandler(event)"/>
		<s:Button id="delItem" x="168" y="104" label="删除选中" click="delItem_clickHandler(event)"/>
	</s:Panel>
</s:Application>