This is an example showing an application of the loader class with all it's handlers - this example is from the Flash help files. Usually you don't need all of them but it's handy to have an overview.
package { import flash.display.Loader; import flash.display.Sprite; import flash.events.*; import flash.net.URLRequest; public class LoaderExample extends Sprite { private var url:String = "Image.gif"; public function LoaderExample() { var loader:Loader = new Loader(); configureListeners(loader.contentLoaderInfo); loader.addEventListener(MouseEvent.CLICK, clickHandler); var request:URLRequest = new URLRequest(url); loader.load(request); addChild(loader); } private function configureListeners(dispatcher:IEventDispatcher):void { dispatcher.addEventListener(Event.COMPLETE, completeHandler); dispatcher.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler); dispatcher.addEventListener(Event.INIT, initHandler); dispatcher.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler); dispatcher.addEventListener(Event.OPEN, openHandler); dispatcher.addEventListener(ProgressEvent.PROGRESS, progressHandler); dispatcher.addEventListener(Event.UNLOAD, unLoadHandler); } private function completeHandler(event:Event):void { trace("completeHandler: " + event); } private function httpStatusHandler(event:HTTPStatusEvent):void { trace("httpStatusHandler: " + event); } private function initHandler(event:Event):void { trace("initHandler: " + event); } private function ioErrorHandler(event:IOErrorEvent):void { trace("ioErrorHandler: " + event); } private function openHandler(event:Event):void { trace("openHandler: " + event); } private function progressHandler(event:ProgressEvent):void { trace("progressHandler: bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal); } private function unLoadHandler(event:Event):void { trace("unLoadHandler: " + event); } private function clickHandler(event:MouseEvent):void { trace("clickHandler: " + event); var loader:Loader = Loader(event.target); loader.unload(); } } }