Here is a sample that shows how to get the item.Take a look at the code "doQuery(event...)" and see how to get the repeater index then get that item from your array.
<?xml version="1.0" encoding="utf-8"?>
<s:Application name="Repeater Test"
xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" xmlns:esri="http://www.esri.com/2008/ags">
<fx:Script>
<![CDATA[
import com.esri.ags.events.QueryEvent;
import mx.controls.Alert;
import mx.states.State;
private function doQuery(event:Event):void
{
var state:String = arrList.getItemAt(event.currentTarget.repeaterIndex).toString();
var where:String = "STATE_NAME = '"+state+"'";
query.where = where;
query.outFields = ["STATE_NAME"];
queryTask.addEventListener(QueryEvent.EXECUTE_COMPLETE, onQueryComplete);
queryTask.execute(query);
}
private function onQueryComplete(result:QueryEvent):void
{
//Alert.show("done");
}
]]>
</fx:Script>
<fx:Declarations>
<s:ArrayList id="arrList" source="[New York,California,Florida]"/>
<esri:QueryTask useAMF="false" id="queryTask" showBusyCursor="true" url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5"/>
<esri:Query id="query" outSpatialReference="{myMap.spatialReference}" returnGeometry="true"/>
</fx:Declarations>
<esri:Map id="myMap">
<esri:extent>
<esri:Extent xmin="-14298000" ymin="2748000" xmax="-6815000" ymax="7117000">
<esri:SpatialReference wkid="102100"/>
</esri:Extent>
</esri:extent>
<esri:ArcGISTiledMapServiceLayer url="http://server.arcgisonline.com/ArcGIS/rest/services/World_Physical_Map/MapServer"/>
<esri:GraphicsLayer id="myGraphicsLayer" graphicProvider="{queryTask.executeLastResult.features}"/>
</esri:Map>
<s:VGroup horizontalCenter="0" verticalCenter="0">
<mx:HBox>
<mx:Repeater id="rpt" dataProvider="{arrList}">
<s:Button click="doQuery(event)" left="20" top="335" label="{rpt.currentItem}" />
</mx:Repeater>
</mx:HBox>
</s:VGroup>
</s:Application>
Drew