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

    <mx:Array id="arr">
        <mx:Object abbrev="AL" name="Alabama" />
        <mx:Object abbrev="AK" name="Alaska" />
        <mx:Object abbrev="AZ" name="Arizona" />
        <mx:Object abbrev="AR" name="Arkansas" />
        <mx:Object abbrev="CA" name="California" />
        <mx:Object abbrev="CO" name="Colorado" />
        <mx:Object abbrev="CT" name="Connecticut" />
    </mx:Array>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="button"
                label="Reset ComboBox"
                click="comboBox.selectedIndex = -1;" />
    </mx:ApplicationControlBar>

    <mx:ComboBox id="comboBox"
            dataProvider="{arr}"
            labelField="name"
            prompt="Please select a state..." />

</mx:Application>