创建联动下拉列表.

原理很简单，改变数据源
示例：

代码：
 

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="middle" backgroundColor="white">

    <mx:XML id="dp" source="countries_states.xml" format="e4x" />

    <mx:Form>
        <mx:FormItem label="Country:">
            <mx:ComboBox id="countryCB" dataProvider="{dp.country}" labelField="@name" />
        </mx:FormItem>
        <mx:FormItem label="State:">
            <mx:ComboBox id="stateCB" dataProvider="{countryCB.selectedItem.state}" />
        </mx:FormItem>
    </mx:Form>

</mx:Application>