TypeError: Error #2007: Parameter hitTestObject must be non-null

[tork612]

I am making a game for with AS3 and have only been doing it for a week but I always get this problem and there is always a different solution each time. could someone help me out. here is the source code(frame 2 of 3 where the main problem is on line 192):

full error:

TypeError: Error #2007: Parameter hitTestObject must be non-null.

  at flash.display::DisplayObject/_hitTest()

  at flash.display::DisplayObject/hitTestObject()

  at collisionwallgame_fla::MainTimeline/greenwinZone()

source code:

import flash.events.Event;

import flash.events.KeyboardEvent;

import flash.display.Sprite;

import flash.events.MouseEvent;

stop();

var hero:Sprite = new Sprite  ;

var characterSpeed:int = 7;

//var prevX:Number = 0;

//var prevY:Number = 0;

hero.x = 133.35;

hero.y = 188;

addChild(hero);

//keyboard movements

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyboardCommands);

function keyboardCommands(e:KeyboardEvent):void

{

  if (e.keyCode == Keyboard.LEFT)

  {

  hero.x -=  5;

  }

  if (e.keyCode == Keyboard.RIGHT)

  {

  hero.x +=  5;

  }

  if (e.keyCode == Keyboard.UP)

  {

  hero.y -=  5;

  }

  if (e.keyCode == Keyboard.DOWN)

  {

  hero.y +=  5;

  }

}

//wall collision detection

stage.addEventListener(Event.ENTER_FRAME, wallblock);

/*function resetXY():void

{

trace(hero.x +" "+prevX);

hero.x = prevX;

hero.y = prevY;

}*/

function wallblock(e:Event)

{

  if (hero.hitTestObject(wall1))

  {

  //prevX = hero.x;

  //prevY = hero.y;

  hero.x +=  7.5;

  }

  /*{

  resetXY()

  }*/

  if (hero.hitTestObject(wall2))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall3))

  {

  hero.x +=  7.5;

  }

  if (hero.hitTestObject(wall4))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall5))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall6))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall7))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall8))

  {

  hero.x -=  7.5;

  }

  if (hero.hitTestObject(wall9))

  {

  hero.y -=  7.5;

  }

  if (hero.hitTestObject(wall10))

  {

  hero.x -=  7.5;

  }

  if (hero.hitTestObject(wall11))

  {

  hero.y +=  7.5;

  }

  if (hero.hitTestObject(wall12))

  {

  hero.x -=  7.5;

  }

  if (hero.hitTestObject(wall13))

  {

  hero.x -=  7.5;

  }

  if (hero.hitTestObject(wall14))

  {

  hero.y +=  7.5;

  }

  if (hero.hitTestObject(wall15))

  {

  hero.y +=  7.5;

  }

  if (hero.hitTestObject(wall16))

  {

  hero.y +=  7.5;

  }

  if (hero.hitTestObject(wall17))

  {

  hero.x +=  7.5;

  }

  if (hero.hitTestObject(wall18))

  {

  hero.y +=  7.5;

  }

}

//adding in enemy sprites

var enemySpeed:int = 2;

var Enemy1:Enemyclass1 = new Enemyclass1  ;

var Enemy2:Enemyclass1 = new Enemyclass1  ;

var Enemy3:Enemyclass1 = new Enemyclass1  ;

var Enemy4:Enemyclass2 = new Enemyclass2  ;

var Enemy5:Enemyclass2 = new Enemyclass2  ;

Enemy1.x = 187;

Enemy1.y = 116;

Enemy2.x = 271;

Enemy2.y = 116;

Enemy3.x = 349;

Enemy3.y = 116;

Enemy4.x = 219;

Enemy4.y = 260;

Enemy5.x = 309;

Enemy5.y = 260;

addChild(Enemy1);

addChild(Enemy2);

addChild(Enemy3);

addChild(Enemy4);

addChild(Enemy5);

function terminate():void

{

  gotoAndStop(3);

  trace("hit");

  removeChild(Enemy1);

  removeChild(Enemy2);

  removeChild(Enemy3);

  removeChild(Enemy4);

  removeChild(Enemy5);

  removeChild(hero);

  stage.removeEventListener(KeyboardEvent.KEY_DOWN, keyboardCommands);

  stage.removeEventListener(Event.ENTER_FRAME, wallblock);

  hero.removeEventListener(Event.ENTER_FRAME, enemyhit);

}

//code that advances you to the next screen)

stage.addEventListener(Event.ENTER_FRAME, greenwinZone)

function greenwinZone(e:Event):void

{

  if (hero.hitTestObject(greenwinzone))                        <============================================= LINE 192

  {

  gotoAndStop(4);

  trace("hit");

  removeChild(Enemy1);

  removeChild(Enemy2);

  removeChild(Enemy3);

  removeChild(Enemy4);

  removeChild(Enemy5);

  removeChild(hero);

  stage.removeEventListener(KeyboardEvent.KEY_DOWN, keyboardCommands);

  stage.removeEventListener(Event.ENTER_FRAME, wallblock);

  hero.removeEventListener(Event.ENTER_FRAME, enemyhit);

  hero.removeEventListener(Event.ENTER_FRAME, greenwinZone);

  }

}

//enemy collision

hero.addEventListener(Event.ENTER_FRAME, enemyhit);

function enemyhit(e:Event):void

{

  if (hero.hitTestObject(Enemy1))

  {

  terminate();

  }

  if (hero.hitTestObject(Enemy2))

  {

  terminate();

  }

  if (hero.hitTestObject(Enemy3))

  {

  terminate();

  }

  if (hero.hitTestObject(Enemy4))

  {

  terminate();

  }

  if (hero.hitTestObject(Enemy5))

  {

  terminate();

  }

}

[Ned Murphy]

Use the trace function before line 192 to see if the greenwinzone object is coming up null before the "hit" trace or after it. 

[tork612]

I did what you asked and the object comes up as null as soon as it hits one of the enemy sprites. it still traces hit, but immediately after the null error shows up.

[Ned Murphy · Accepted solution]

It sounds like the function does not stop executing when it should.  I think I can see why now that I take a closer look.  You assign the event listener that calls that function to the stage (~ line 189), but then you try to remove that event listener from the hero (~ line 205).

[tork612]

I have fixed the problem, what I did was set the event listener for winning on line 189 to hero as opposed  to stage, and inserted hero.removeEventListener(Event.ENTER_FRAME, greenwinZone) into the terminate function. your really helped me out with this one thanks!

[Ned Murphy]

You're welcome