Another stage access question

1

I ran into the stage access problem in a project I’m working on and, rather than passing on the actual project, I’ve simplified it in a smaller test project to illustrate my problem.

Here’s the .fla:


var greenSquare:Sprite = new Sprite();
greenSquare.graphics.beginFill(0x00FF00);
greenSquare.graphics.drawRect(-30, -30, 60, 60);
greenSquare.graphics.endFill();
addChild(greenSquare);
greenSquare.x = stage.stageWidth/2;
greenSquare.y = stage.stageHeight/2;
var littleSquare1:Sprite = new Sprite();
littleSquare1.graphics.beginFill(0xFF0000);
littleSquare1.graphics.drawRect(-10, -10, 20, 20);
littleSquare1.graphics.endFill();
addChild(littleSquare1);
littleSquare1.x = 475;
littleSquare1.y = 200;
littleSquare1.addEventListener(MouseEvent.CLICK, moveToLittleSquare1);
function moveToLittleSquare1(e:MouseEvent) {
 blueSquare.x = littleSquare1.x;
 blueSquare.y = littleSquare1.y;
}
var littleSquare2:Sprite = new Sprite();
littleSquare2.graphics.beginFill(0xFF0000);
littleSquare2.graphics.drawRect(-10, -10, 20, 20);
littleSquare2.graphics.endFill();
addChild(littleSquare2);
littleSquare2.x = 275;
littleSquare2.y = 350;
littleSquare2.addEventListener(MouseEvent.CLICK, moveToLittleSquare2);
function moveToLittleSquare2(e:MouseEvent) {
 blueSquare.x = littleSquare2.x;
 blueSquare.y = littleSquare2.y;
}
var littleSquare3:Sprite = new Sprite();
littleSquare3.graphics.beginFill(0xFF0000);
littleSquare3.graphics.drawRect(-10, -10, 20, 20);
littleSquare3.graphics.endFill();
addChild(littleSquare3);
littleSquare3.x = 75;
littleSquare3.y = 200;
littleSquare3.addEventListener(MouseEvent.CLICK, moveToLittleSquare3);
function moveToLittleSquare3(e:MouseEvent) {
 blueSquare.x = littleSquare3.x;
 blueSquare.y = littleSquare3.y;
}
var littleSquare4:Sprite = new Sprite();
littleSquare4.graphics.beginFill(0xFF0000);
littleSquare4.graphics.drawRect(-10, -10, 20, 20);
littleSquare4.graphics.endFill();
addChild(littleSquare4);
littleSquare4.x = 275;
littleSquare4.y = 50;
littleSquare4.addEventListener(MouseEvent.CLICK, moveToLittleSquare4);
function moveToLittleSquare4(e:MouseEvent) {
 blueSquare.x = littleSquare4.x;
 blueSquare.y = littleSquare4.y;
}
var blueSquare:Sprite = new Sprite();
blueSquare.graphics.beginFill(0x0000FF);
blueSquare.graphics.drawRect(-30, -30, 60, 60);
blueSquare.graphics.endFill();
addChild(blueSquare);
blueSquare.x = littleSquare1.x;
blueSquare.y = littleSquare1.y;
var movingDot:DotMove;
stage.addEventListener(KeyboardEvent.KEY_DOWN, startDot);
function startDot(evt:KeyboardEvent):void {
 if (evt.keyCode == 32) {// spacebar
  go();
 }
}
stage.addEventListener(KeyboardEvent.KEY_DOWN, stopDot);
function stopDot(evt:KeyboardEvent):void {
 if (evt.keyCode == 17) {// CTRL key
  removeChild(movingDot);
 }
}
function go():void {
 movingDot = new DotMove(blueSquare.x, blueSquare.y, greenSquare.x, greenSquare.y);
 addChild(movingDot);
}

Here’s DotMove.as:


package {
 import flash.display.*;
 import flash.events.*;
 import flash.utils.Timer;
 public class DotMove extends Sprite {
  private var dot:Sprite;
  private var step:Number = 0.1;
  private var timer:Timer;
  private var x1:Number;
  private var y1:Number;
  private var x2:Number;
  private var y2:Number;
  public function DotMove(x1, y1, x2, y2):void {
   init(x1, y1, x2, y2);
  }
 
  function init(x1, x2, y1, y2) {
   dot = new Sprite();
   dot.graphics.beginFill(0x000000);
   dot.graphics.drawCircle(-2, -2, 4);
   dot.graphics.endFill();
   addChild(dot);
   dot.x = x1;
   dot.y = y1;
   timer.addEventListener(TimerEvent.TIMER, translate);
   timer.start();
  }
 
  function translate(e:TimerEvent):void {
   trace("in translate");
  }
 }
}

The actual functionality I’m looking for is, when I hit the spacebar, the dot moves from the blue square to the green square. I’ve left out that code and only included a trace.

When I hit the spacebar, I get this standard error: “Error #1009: Cannot access a property or method of a null object reference.” My problem is this:

I know that I can get access to the stage in the DotMove class by changing this…


  public function DotMove():void {
   init();
  }
 
  function init() {

…to this…


  public function DotMove():void {
   addEventListener(Event.ADDED_TO_STAGE, init);
  }
 
  function init(event:Event) {

My problem is that I need to pass (x1, x2, y1, y2) to DotMove.

How can I pass (x1, x2, y1, y2) to DotMove, and to init, if init’s argument is already (event:Event)?

Thanks!