为什么我的鲨鱼在与其他鲨鱼相撞时不会受伤？

Question

我的输出也出现错误，例如：

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()[

场景 1 - 主菜单

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);

场景 2 - 游戏

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");
}

场景 3 - 你活下来了

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");

}场景 4 - 游戏结束

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

如评论中所述，您需要删除可以通过以下方式实现的 eventListener：

removeEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally);。

我建议您在绑定到 Event.ENTER_FRAME

等框架事件时执行以下行

this.addEventListener(Event.REMOVED_FROM_STAGE, function(){
    try{
         removeEventListener(Event.ENTER_FRAME, fl_AnimateHorizontally);
    }catch(error){
         //error handling optional in this case.
    }
});

这只会在对象从舞台 destroyed/removed 之前调用一次，即当您调用 MovieClip(this.root).gotoAndPlay(1, "Game");

时

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.

为什么我的鲨鱼在与其他鲨鱼相撞时不会受伤？

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

flash

actionscript-3