Why does my shark not get damaged when colliding with other sharks? - actionscript-3

Question

I also get errors on my output such as:
TypeError: Error #1009: Cannot access a property or method of a null
object reference. at
AttackonSharkwithMovement_fla::MainTimeline/fl_AnimateHorizontally()
TypeError: Error #1009: Cannot access a property or method of a null
object reference. at
AttackonSharkwithMovement_fla::MainTimeline/fl_AnimateHorizontally_2()
TypeError: Error #1009: Cannot access a property or method of a null
object reference. at
AttackonSharkwithMovement_fla::MainTimeline/fl_EnterFrameHandler_2()[
Scene 1 - Main Menu
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
import flash.display.MovieClip;
import flash.events.Event;
import flash.display.Stage;
import flash.system.fscommand
import flash.events.MouseEvent
stop();
//Button Scripts
Play_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene);
function fl_ClickToGoToScene(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Game");
}
Instructions_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndStopAtFrame_10);
function fl_ClickToGoToAndStopAtFrame_10(event:MouseEvent):void
{
gotoAndStop(6);
}
function quit (event:MouseEvent):void
{
fscommand ("quit");
}
Quit_Button.addEventListener(MouseEvent.MOUSE_DOWN,quit);
Scene 2 - Game
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
import flash.display.MovieClip;
import flash.events.Event;
import flash.display.Stage;
import flash.system.fscommand;
import flash.events.TimerEvent;
import flash.utils.Timer;
stop();
//Variables
var rightPressed:Boolean = new Boolean(false);
var leftPressed:Boolean = new Boolean(false);
var upPressed:Boolean = new Boolean(false);
var downPressed:Boolean = new Boolean(false);
var sharkSpeed:Number = 10;
var score1:Number = 0;
var maxHP:int = 100;
var currentHP:int = maxHP;
var percentHP:Number = currentHP / maxHP;
//Health Script
function updateHealthBar():void
{
percentHP = currentHP / maxHP;
healthBar.barColor.scaleX = percentHP;
}
//Button Scripts
MainMenu_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene_2);
function fl_ClickToGoToScene_2(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Main Menu");
}
Instructions_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToNextScene_2);
function fl_ClickToGoToNextScene_2(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(6, "Main Menu");
}
//Keyboard Movement
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
stage.addEventListener(KeyboardEvent.KEY_UP, keyUpHandler);
stage.addEventListener(Event.ENTER_FRAME, gameLoop);
function keyDownHandler(KeyEvent:KeyboardEvent):void
{
if (KeyEvent.keyCode == Keyboard.RIGHT)
{
rightPressed = true;
}
else if (KeyEvent.keyCode == Keyboard.LEFT)
{
leftPressed = true;
}
else if (KeyEvent.keyCode == Keyboard.DOWN)
{
downPressed = true;
}
else if (KeyEvent.keyCode == Keyboard.UP)
{
upPressed = true;
}
}
function keyUpHandler(keyEvent:KeyboardEvent):void
{
if (keyEvent.keyCode == Keyboard.RIGHT)
{
rightPressed = false;
}
else if (keyEvent.keyCode == Keyboard.LEFT)
{
leftPressed = false;
}
else if (keyEvent.keyCode == Keyboard.DOWN)
{
downPressed = false;
}
else if (keyEvent.keyCode == Keyboard.UP)
{
upPressed = false;
}
}
function gameLoop(loopEvent:Event):void
{
if (rightPressed)
{
shark.x += sharkSpeed;
}
else if (leftPressed)
{
shark.x -= sharkSpeed;
}
else if (downPressed)
{
shark.y += sharkSpeed;
}
else if (upPressed)
{
shark.y -= sharkSpeed;
}
}
//AI Movement
addEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally);
function fl_AnimateHorizontally(event:Event)
{
enemy1.x += 2;
enemy2.x += 2;
enemy3.x += 2;
enemy4.x += 2;
enemy5.x += 2;
enemy6.x += 2;
megaladon.x += 2;
}
addEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally_2);
function fl_AnimateHorizontally_2(event:Event)
{
fishes.x += 1.5;
}
//Colission
function hitsTheObject(e:Event)
{
if (shark.hitTestObject(enemy1))
{
trace("player collided with enemy");
currentHP -= 50;
if (currentHP <= 0)
{
currentHP = 0;
trace("You died!");
MovieClip(this.root).gotoAndPlay(1, "Game Over");
}
updateHealthBar();
}
}
//Score Script
addEventListener(Event.ENTER_FRAME, fl_EnterFrameHandler_2);
function fl_EnterFrameHandler_2(event:Event):void
{
gameScore.text = String(score1);
score1 += 1;
trace("gameScore.text is : " + gameScore.text);
trace("score1 is : " + score1);
}
//Timer Script
var myTimer:Timer = new Timer(1000,50);
myTimer.addEventListener(TimerEvent.TIMER, onTimer);
myTimer.addEventListener(TimerEvent.TIMER_COMPLETE, onComplete);
myTimer.start();
function onTimer(e: TimerEvent):void
{
myText_txt.text = String(myTimer.repeatCount - myTimer.currentCount);
}
function onComplete(e: TimerEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "You Survived");
}
Scene 3 - You Survived
stop();
//Button Scripts
MainMenu_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene_4);
function fl_ClickToGoToScene_4(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Main Menu");
}
PlayAgain_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene_12);
function fl_ClickToGoToScene_12(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Game");
}Scene 4 - Game Over
stop();
//Button Scripts
MainMenu_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene_9);
function fl_ClickToGoToScene_9(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Main Menu");
}
PlayAgain_Button.addEventListener(MouseEvent.CLICK, fl_ClickToGoToScene_11);
function fl_ClickToGoToScene_11(event:MouseEvent):void
{
MovieClip(this.root).gotoAndPlay(1, "Game");
}

Answer 1

As identified in the comments, you need to remove the eventListener which you can achieve with:
removeEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally);.
I would suggest implementing the following line whenever you bind to a frame event such as Event.ENTER_FRAME
this.addEventListener(Event.REMOVED_FROM_STAGE, function(){
try{
removeEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally);
}catch(error){
//error handling optional in this case.
}
});
This will get called ONCE only right before the object is destroyed/removed from the stage i.e. when you call MovieClip(this.root).gotoAndPlay(1, "Game");
Note: You can just put all of your 'global' events into the try area - you don't need this call every time you add an event.
Additionally, you don't need this whatsoever for movieclips as all of your events will get cleaned up automatically once they are removed from the stage via the garbage collector.