apache-flex - 通过 Flex 4 中的 ActionScript 选择 DropDownList 的值

Question

我确信这是一个简单的方法，但我一直在寻找如何使用 actionscript 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 - 如果你需要使用标签或值来做到这一点，你可以像这样循环遍历 arraycollection:

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，或者从应用程序的其他部分获取时区，则可以更简洁地进行:

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进入它们。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，它也会更容易。