在 Flex 4 中通过动作脚本选择 DropDownList 的值

Question

我确信这很简单，但我一直在寻找如何使用动作脚本选择 DropDownList 元素。在这种情况下，我希望能够基于 ddlLabel 或 ddlData 指定 selectedItem

<?xml version="1.0" encoding="utf-8"?>

<fx:Script>
    <![CDATA[
        import mx.collections.ArrayCollection;
        import mx.events.FlexEvent;

        [Bindable]
        protected var timezonesArray:ArrayCollection = new ArrayCollection([
            {ddlLabel:"Eastern Time", ddlData:"EST"}, 
            {ddlLabel:"Central Time", ddlData:"CST"}, 
            {ddlLabel:"Mountain Time", ddlData:"MST"}, 
            {ddlLabel:"Pacific Time", ddlData:"PST"}
        ]);

        protected function windowedapplication1_creationCompleteHandler(event:FlexEvent):void
        {
            // I'm looking to select an element via actionscript here, based on ddlLabel or ddlData
        }

    ]]>
</fx:Script>

<mx:Form>
    <s:DropDownList id="ddlTimezones" dataProvider="{timezonesArray}" labelField="ddlLabel"/>
</mx:Form>

Answer 1

有几种方法可以做到这一点 - 如果您需要使用标签或值来执行此操作，您可以像这样循环遍历数组集合：

protected function windowedapplication1_creationCompleteHandler(event:FlexEvent):void
{
    var searchTerm:String = "EST";
    var result:* = null;
    for each(var zone:* in timeZonesArray)
    {
        if(searchTerm == zone.ddlData)
        {
            result = zone;
            break;
        }
    }
    ddlTimezones.selectedItem = result;
}

但是，如果您单独保留对时区的引用或者从以下位置获取它们在应用程序的其他部分，您可以做得更干净：

import mx.collections.ArrayCollection;
import mx.events.FlexEvent;


var EST:Object = {ddlLabel:"Eastern Time", ddlData:"EST"};
var CST:Object = {ddlLabel:"Central Time", ddlData:"CST"};
var MST:Object = {ddlLabel:"Mountain Time", ddlData:"MST"};
var PST:Object = {ddlLabel:"Pacific Time", ddlData:"PST"};

[Bindable]
protected var timezonesArray:ArrayCollection = new ArrayCollection([
    EST, 
    CST, 
    MST, 
    PST
]);

protected function windowedapplication1_creationCompleteHandler(event:FlexEvent):void
{
    ddlTimezones.selectedItem = EST;
}

这样，您不必担心询问列表中的每个对象，因为您停留在整个对象的级别而不是触及它们。如果您想用类定义替换 JSON 样式对象列表，如果您开始需要存储有关时区的更复杂的信息，它也会变得更容易。