Can't get stage from a constructor method. Why?

Question

Hi,
I'm making a kind of image showcase, what has a fluid width and height, depending on browser window dimensions. Everything is okay, I have other kind of issue: in constructor function in this gallery class I can't use stage property, I have to get it from main class.
Why Flash treats me this way and how I can avoid this currentStage variable?
Main code:
package dev {
     import flash.display.Sprite;
     import flash.display.StageScaleMode;
     import flash.display.StageAlign;
     import flash.display.MovieClip;
     import flash.events.Event;
     import UI.BackgroundImageRotator;
     public class Application extends Sprite {
          public function Application():void {
               stage.scaleMode = StageScaleMode.NO_SCALE;
               stage.align = StageAlign.TOP_LEFT;
               trace("Start.");
               var BIR = new BackgroundImageRotator(stage);
               stage.addChild(BIR);
BackgroundImageRotator class:
package UI {
     import flash.display.MovieClip;
     import flash.events.Event;
     import flash.display.Stage;
     public class BackgroundImageRotator extends MovieClip {
          protected var currentStage:Stage;
          public function BackgroundImageRotator(currentStage:Stage):void {
               this.x = 0;
               this.y = 0;
               this.currentStage = currentStage;
               currentStage.addEventListener(Event.RESIZE, onStageResize);
          protected function onStageResize(evt:Event):void {
               trace(stage.stageWidth + ' ' + stage.stageHeight);

Answer 1

if you have a display object that will be added to the display list, you need to wait until it is added before you can reference its stage property.  ie, use the Event.ADDED_TO_STAGE event.
otherwise, you must pass a stage reference to your class.