package org.epayam.AppName {	
	import com.greensock.events.LoaderEvent;
	import com.greensock.loading.LoaderMax;
	import com.greensock.loading.XMLLoader;
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.events.Event;
	import org.epayam.AppName.ast.Dta;
	
	public class Main extends Sprite {
		
		public static var p:Sprite; //path
		
		private const initFileUrl:String = "xml/SomeFile.xml";
		
		public function Main():void {
			if (stage) {
				init();
			} else {
				addEventListener(Event.ADDED_TO_STAGE, init);
			}
		}
		
		/*~~~~~~~~~~~~~~~~~~~~~~~~(Private)~~~~~~~~~~~~~~~~~~~~~~~*/
		private function init(e:Event = null):void {
			removeEventListener(Event.ADDED_TO_STAGE, init);
			loadInitFiles();
		}
		
		private function loadInitFiles():void {			
			var loader:XMLLoader = new XMLLoader(initFileUrl, {name: "data",
                        onComplete: dataLoaded});
			loader.load();
		}
		
		private function dataLoaded(e:LoaderEvent):void {
			setData();
			setupApp();
			showApp();
		}
		
		private function setData():void {
			Dta.pgeTxt = LoaderMax.getContent("data");
		}
		
		private function setupApp():void {			
			stage.scaleMode = StageScaleMode.NO_SCALE;
			stage.align = StageAlign.TOP_LEFT;
			App.p = this; // to be found by other classes
		}
		
		private function showApp():void {
			app.init(); // an empty frame for loagding pages
		}
	}
}

Often in my apps, some primary data are needed to be loaded, saved and then the App start to load the first page. Here is the best Main class I have so far come up with, that I use for my own apps.

Main - Air for Mobile

ActionScript 3