ActionScript 3: Creating custom event handlers using EventDispatcher

Creating custom event handlers in ActionScript 3 is pretty much simple. Here is a simple example which loads an image and fires a custom event named “onImageLoad” as soon as image is loaded.

Class imageLoader.as

package {
import flash.events.*;
import flash.net.URLRequest;
import flash.display.Loader;
import flash.display.Sprite;
public class imageLoader extends EventDispatcher {
private var _mc:Sprite;
private var url:String;
private var loader:Loader;
public function imageLoader(_mc:Sprite, url:String) {
this._mc = _mc;
this.url = url;
loadImg();
_mc.addChild(loader);
}
private function loadImg():void {
loader = new Loader();
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onComplete);
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, onIOError);
var request:URLRequest = new URLRequest(url);
loader.load(request);
}
private function onComplete(event:Event):void {
dispatchEvent(new Event("onImageLoad"));
}
private function onIOError(event:IOErrorEvent):void {
trace("IO Error.");
}
}
}

Now in Flash, create a a object of imageLoader class and add a event listener (for our custom event “onImageLoad”).

var myImageLoader:imageLoader = new imageLoader(this, "images/someImg.jpg");
myImageLoader.addEventListener("onImageLoad", callbackHandler);
function callbackHandler(event:Event) {
trace("Image Loading Complete!");
}

Now test the file. Be sure to have someImg.jpg in images folder. Once image is loaded, you should be able to see ”"Image Loading Complete!” message in output window.

About these ads