Question

I have the following code:

package ;

import flash.display.DisplayObject;
import flash.display.Graphics;
import flash.display.MovieClip;
import flash.display.Shape;
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.Rectangle;
import flash.Lib;
import flash.utils.Timer;

/**
 * ...
 * @author RCIX
 */

class Main 
{
 static function main()
 {
  trace("game started");
  var game : Game = new Game();
  game.Run();
  trace("game finished");
 }
}
class Game extends DisplayObject
{
 var rectX : Int;
 var rectY : Int;
 var velocityX : Int;
 var velocityY : Int;

 var screenBounds : Rectangle;
 var graphics : Graphics;

 public function new()
 {
  super();
  screenBounds = Lib.current.getBounds(new DisplayObject());
  graphics = Lib.current.graphics;
  Lib.current.addChild(this);
  trace("Game constructor");
 }

 public function Run()
 {
  trace("Run");
  Lib.current.addEventListener(Event.ENTER_FRAME, OnFrameEnter);
  velocityX = 1;
  velocityY = 1;
 }
 function OnFrameEnter(event : Event)
 {
  trace("OnFrameEnter");
  graphics.beginFill(0xFFFFFF, 0xFFFFFF);
  graphics.drawRect(0, 0, screenBounds.width, screenBounds.height);
  graphics.endFill();
  Update();
 }
 function Update()
 {
  trace("Updating");
  if (rectX + 50 > screenBounds.width || 
      rectX < 0)
  {
   velocityX *= -1;
  }
  if (rectY + 50 > screenBounds.height || 
      rectY < 0)
  {
   velocityY *= -1;
  }
  rectX += 1;
  rectY += 1;
  graphics.beginFill(0xFF0000);
  graphics.drawRect(rectX, rectY, 50, 50);
  graphics.endFill();
 }
}

but the only trace output i get is “Game started”; nothing else is tracing or working. Why?

Update: After having fixed the screenBounds problem, the following problems remain:

• None of my OnFrameEnter or Update calls ever trace; why?
• Extending my Game class from DisplayObject makes things grind to a halt and never get to any of my other code, regardless of whether i call super(); in the constructor.

Update: since the first problem is a separate issue, i’m splitting that out into another question.

Answer 1

From AS3 language reference:

DisplayObject is an abstract base class; therefore, you cannot call DisplayObject directly. Invoking new DisplayObject() throws an ArgumentError exception.

So basically you should extends Shape or Sprite instead of DisplayObject.