DropDownList

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2023-12-01

介绍 (Introduction)

DropDownList控件包含一个下拉列表，用户可以从中选择与HTML中的SELECT表单元素类似的单个值。

Class 声明 (Class Declaration)

以下是spark.components.DropDownList类的声明 -

public class DropDownList 
   extends DropDownListBase

公共属性 (Public Properties)

S.No	财产和描述
1	prompt : String DropDownList控件的提示。
2	typicalItem : Object [override]当需要固定的行或列大小时，布局使用typicalItem的首选大小，但未设置特定的rowHeight或columnWidth值。

S.No

财产和描述

prompt : String

DropDownList控件的提示。

typicalItem : Object

[override]当需要固定的行或列大小时，布局使用typicalItem的首选大小，但未设置特定的rowHeight或columnWidth值。

公共方法 (Public Methods)

S.No	方法和描述
1	DropDownList() 构造函数。

方法继承 (Methods Inherited)

该类继承以下类中的方法 -

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控件示例

让我们按照以下步骤通过创建测试应用程序来检查Flex应用程序中DropDownList控件的用法 -

步	描述
1	在cn.xnip.client包下创建一个名为HelloWorld的项目，如Flex - Create Application一章中所述。
2	修改HelloWorld.mxml ，如下所述。保持其余文件不变。
3	编译并运行应用程序以确保业务逻辑按照要求运行。

以下是修改后的mxml文件src/cn.xnip/HelloWorld.mxml 。

<?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/xnip/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>

一旦准备好完成所有更改，让我们像在Flex - Create Application章节中那样在正常模式下编译和运行应用程序。