Flex - 下拉列表控制元件

簡介

DropDownList 控制元件包含一個下拉列表，使用者可以從中選擇單個值，類似於 HTML 中的 SELECT 表單元素。

類宣告

以下是 **spark.components.DropDownList** 類的宣告：

public class DropDownList 
   extends DropDownListBase 

公共屬性

公共方法

繼承的方法

此類繼承自以下類：

• spark.components.supportClasses.DropDownListBase
• spark.components.List
• spark.components.supportClasses.ListBase
• spark.components.SkinnableDataContainer
• spark.components.supportClasses.SkinnableContainerBase
• spark.components.supportClasses.SkinnableComponent
• mx.core.UIComponent
• mx.core.FlexSprite
• flash.display.Sprite
• flash.display.DisplayObjectContainer
• flash.display.InteractiveObject
• flash.display.DisplayObject
• flash.events.EventDispatcher
• Object

Flex DropDownList 控制元件示例

讓我們按照以下步驟，透過建立一個測試應用程式來檢查 Flex 應用程式中 DropDownList 控制元件的使用：

以下是修改後的 mxml 檔案 **src/com.tutorialspoint/HelloWorld.mxml** 的內容。

<?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"
   xmlns:mx = "library://ns.adobe.com/flex/mx"
   width = "100%" height = "100%" minWidth = "500" minHeight = "500">

   <fx:Style source = "/com/tutorialspoint/client/Style.css" />
   <fx:Script>
      <![CDATA[
         import mx.collections.ArrayCollection; 
         import spark.events.IndexChangeEvent;
		 
         [Bindable]
         public var data:ArrayCollection = new ArrayCollection (
         [   
            {value:"France", code:"FR"},
            {value:"Japan", code:"JP"},
            {value:"India", code:"IN"},
            {value:"Russia", code:"RS"},
            {value:"United States", code:"US"}		
         ]                
         );

         protected function dropDownList_changeHandler
           (event:IndexChangeEvent):void {
            ddlIndex.text = dropDownList.selectedIndex.toString();
            ddlSelectedItem.text = dropDownList.selectedItem.value;
            ddlCode.text = dropDownList.selectedItem.code;
         }

      ]]>
   </fx:Script>

   <s:BorderContainer width = "550" height = "400" id = "mainContainer"
      styleName = "container">
      <s:VGroup width = "100%" height = "100%" gap = "50" horizontalAlign = "center"
         verticalAlign = "middle">
         <s:Label id = "lblHeader" text = "Form Controls Demonstration" 
            fontSize = "40" color = "0x777777" styleName = "heading" />
         
         <s:Panel id = "dropDownListPanel" title = "Using DropDownList" 
            width = "420" height = "200">
            <s:layout>
               <s:VerticalLayout  gap = "10" verticalAlign = "middle" 
                  horizontalAlign = "center" />	
            </s:layout>
            
            <s:HGroup>
               <s:Label text = "Index :" />
               <s:Label id = "ddlIndex" fontWeight = "bold" />
               <s:Label text = "Value :" /> 
               <s:Label id = "ddlSelectedItem" 
                  text = "{dropDownList.selectedItem.value}" fontWeight = "bold" />
               <s:Label text = "Code :" /> 
               <s:Label id = "ddlCode" 
                  text = "{dropDownList.selectedItem.code}" fontWeight = "bold" />
            </s:HGroup>				
            
            <s:DropDownList id = "dropDownList" dataProvider = "{data}" 
               width = "150" change = "dropDownList_changeHandler(event)"
               selectedIndex = "0" labelField = "value" />     				
         </s:Panel>
      </s:VGroup>	 
   </s:BorderContainer>	
</s:Application>

完成所有更改後，讓我們像在“Flex - 建立應用程式”一章中一樣，以普通模式編譯並執行應用程式。如果應用程式一切正常，它將產生以下結果：[ 線上嘗試 ]