ArgumentError: Removing Child from Stage

Question

I am trying to develop a basic Snake game that involves some inverse kinematics and state machines. I'm trying to get it so when the first segment of the snake interacts with a certain "mouse", it disappears. However, when I do, it doesn't work and I end up getting ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.

Here's my code:

package 
{
 import agent.Agent;
 import flash.display.Sprite;
 import flash.display.StageAlign;
 import flash.display.StageScaleMode;
 import flash.events.Event;
 import flash.events.MouseEvent;
 import flash.events.KeyboardEvent;
 import flash.geom.Point;
 public class Main extends Sprite 
 {
  private var Agents:Vector.<Agent>;
    private var segments:Array;
  private var numSegments:uint = 150;
  private var player:Point = new Point (15, 15)
  public function Main():void 
  {
   if (stage) init();
   else addEventListener(Event.ADDED_TO_STAGE, init);
  }
  
  private function init(e:Event = null):void 
  {
   stage.align = StageAlign.TOP_LEFT;
   stage.scaleMode = StageScaleMode.NO_SCALE;
   segments = new Array();
   for(var i:uint = 0; i < numSegments; i++)
   {
    var segment:Segment = new Segment (5, 10);
    addChild(segment);
    segments.push(segment);
   }
   //updatePoint();
   addEventListener(Event.ENTER_FRAME, onEnterFrame);

   removeEventListener(Event.ADDED_TO_STAGE, init);
   stage.scaleMode = StageScaleMode.NO_SCALE;
   stage.align = StageAlign.TOP_LEFT;
   // entry point
   graphics.beginFill(0xeeeeee);
   graphics.drawRect(0, 0, stage.stageWidth, stage.stageHeight);
   
   Agents = new Vector.<Agent>();
   addEventListener(Event.ENTER_FRAME, gameloop);
   for (var x:int = 0; x < 10; x++) 
   {
    var a:Agent = new Agent();
    addChild(a);
    Agents.push(a);
    a.x = Math.random() * 10;
    a.y = Math.random() * 10;
   }
   stage.addEventListener(MouseEvent.CLICK, createAgent);
  }
  
  private function createAgent(e:MouseEvent):void 
  {
   var a:Agent = new Agent();
   stage.addChild(a);
   Agents.push(a);
   a.x = mouseX;
   a.y = mouseY;
  }
  
  private function gameloop(e:Event):void 
  {
   for each (var a: Agent in Agents) {
    a.update();
    trace ("Follow me on Twitter.");
    for each(var target: Segment in segments)
    {
     if (target.hitTestPtarget.x, a.y + target.y, true))
     {
      stage.removeChild(a);
     }
    }
    
   }
  }
  private function onEnterFrame(event:Event):void
  {
   drag(segments[0], player.x, player.y);
   stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDown);

   for(var i:uint = 1; i < numSegments; i++)
   {
    var segmentA:Segment = segments[i];
    var segmentB:Segment = segments[i - 1];
    drag(segmentA, segmentB.x, segmentB.y);
   }
  }
  private function keyDown (evt: KeyboardEvent): void {
   //87=w 68=d 83=s 65=a
   if (evt.keyCode == 87) 
   {
    player.y-=50;
   } 
   else if (evt.keyCode == 83) 
   {
    player.y+=50;
   } 
   else if (evt.keyCode == 68) 
   {
    player.x+=50;
   } 
   else if (evt.keyCode == 65) 
   {
    player.x-=50;
   }
   trace (player.x + " " + player.y);
  }
  private function drag(segment:Segment, xpos:Number, ypos:Number):void
  {
   
   var dx:Number = xpos - segment.x;
   var dy:Number = ypos - segment.y;
   var angle:Number = Math.atan2(dy, dx);
   segment.rotation = angle * 180 / Math.PI;
   
   var w:Number = segment.getPin().x - segment.x;
   var h:Number = segment.getPin().y - segment.y;
   segment.x = xpos - w;
   segment.y = ypos - h;
  }

  
 }
}

I have tried looking at other posts with the same topic, but I just don't understand what I'm doing wrong. Any help would be greatly appreciated!

score 2 · Answer 1 · answered Nov 23 '16 at 13:42

You are adding Agents and Segments locally (in Main) and later you are trying to remove them from the stage (which is the top level of the swf and is an another display object).

Either do stage.addChild(...) in your init function or (this is a better option imo) replace stage.removeChild(...) with a removeChild(...) everywhere else - this will keep the objects in a local Main space (who knows, maybe you would want to move around your Main later, make everything invisible at once etc).

ArgumentError: Removing Child from Stage

1 Answers1