2

对于一个 DropDownList，我有两个 dataProvider。下面的代码可以编译运行。

<?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"
   creationComplete="flipLast()"
   minWidth="955" minHeight="600">
<fx:Script>
<![CDATA[
     import mx.collections.ArrayCollection;
     public function flipLast():void {
          if( last ) {
               list.dataProvider = dp1;
               list.selectedItem = "Flex";
          } else {
               list.dataProvider = dp2;
               list.selectedItem = "Catalyst";        
          }
          last = !last;
     }

     public var last:Boolean = true;
     public var dp1:ArrayCollection = new ArrayCollection( [ "Flex", "Air" ] );
     public var dp2:ArrayCollection = new ArrayCollection( [ "Catalyst", "FlashBuilder" ] );
]]>
</fx:Script>

<s:VGroup>
     <s:DropDownList id="list" requireSelection="true" />

     <s:Label id="listSelectedItem" text="{list.selectedItem}" />
     <s:Label id="listSelectedIndex" text="{list.selectedIndex}" />

     <s:Button label="Flip" click="flipLast()" />
</s:VGroup>
</s:Application>

场景一：dataProvider 更新了，但是 selectedIndex 是一样的。启动时：[ listSelectedItem=Flex, listSelectedIndex=1 ]。单击翻转：dataProvider 已更新，但仍为 [ listSelectedItem=Flex, listSelectedIndex=1 ]。

场景二：dataProvider 更新，selectedIndex 也更新。启动时：[ listSelectedItem=Flex, listSelectedIndex=1 ]。从列表中选择 Air：[ listSelectedItem=Air, listSelectedIndex=2 ]。单击翻转：dataProvider 已更新，但仍为 [ listSelectedItem=Catalyst, listSelectedIndex=1 ]。

在我看来，selectedItem 是由 selectedIndex 驱动的。selectedItem 仅在 selectedIndex 更新时更新。更新 dataProvider 时不应该更新 selectedItem 吗？绑定到 selectedItem 有缺陷吗？

4

1 回答 1

2

也许你认为它坏了是对的。我不会对此做出判断。不过，解决您的问题非常简单，更改翻转功能以重置选定索引，从而触发列表上的数据更改，并最终绑定到您的组件：

public function flipLast():void {
          list.selectedIndex = -1;
          if( last ) {
               list.dataProvider = dp1;
               list.selectedItem = "Flex";
          } else {
               list.dataProvider = dp2;
               list.selectedItem = "Catalyst";        
          }
          last = !last;
     }
于 2010-12-28T12:45:21.693 回答