private function button1_clickHandler(event:MouseEvent):void
{
var servA:ArcGISDynamicMapServiceLayer = map.getLayer("serviceA") as ArcGISDynamicMapServiceLayer;
var servB:ArcGISDynamicMapServiceLayer = map.getLayer("serviceB") as ArcGISDynamicMapServiceLayer;
servA.visibleLayers = new ArrayCollection([0]);
servB.visibleLayers = new ArrayCollection([1,2]);
}
private function button2_clickHandler(event:MouseEvent):void
{
var servA:ArcGISDynamicMapServiceLayer = map.getLayer("serviceA") as ArcGISDynamicMapServiceLayer;
var servB:ArcGISDynamicMapServiceLayer = map.getLayer("serviceB") as ArcGISDynamicMapServiceLayer;
servA.visibleLayers = new ArrayCollection([1]);
servB.visibleLayers = new ArrayCollection([0]);