Greenfoot

2019/1/11

Moving Scenery NullPointerException

2019/1/11

This is the same project I have posted about recently: Click Here This time when I try to run it the greenfoot terminal pops up and throws an exception:

My World code is here:

import greenfoot.*;

public class OverWorld extends World
{
    public OverWorld()
    {    
        super(1200, 800, 1, false); //Creates a new world measuring 1200 x 800 cells with a cell size of 1x1 pixels and no boundaries.
        prepare();
    }
    private Jumper jumper;
    public Jumper getDidBumpHead() {
        return jumper;
    }
    public Jumper getIsOnSolidGround() {
        return jumper;
    }
    public Jumper getCanMoveLeft() {
        return jumper;
    }
    public Jumper getCanMoveRight() {
        return jumper;
    }
    private void prepare()
    {
        setPaintOrder(Jumper.class, Platform.class);
        Jumper jumper = new Jumper();
        addObject(jumper, 600, 400);
        Scenery scenery = new Scenery(3600, 2400);
        addObject(scenery, 600, 400);
        Platform platform = new Platform(50, 1200);
        addObject(platform, 1800, 400);
    }
}

My 'Scenery' code is here:

import greenfoot.*;

public class Scenery extends Actor
{
    private int step = 3;
    private boolean DBH = false;
    private boolean IOSG = false;
    private boolean CML = false;
    private boolean CMR = false;
    public void boolSet() {
        if(((OverWorld) getWorld()).getDidBumpHead().didBumpHead()) DBH = true;
        else if(!((OverWorld) getWorld()).getDidBumpHead().didBumpHead()) DBH = false;
        if(((OverWorld) getWorld()).getIsOnSolidGround().isOnSolidGround()) IOSG = true;
        else if(!((OverWorld) getWorld()).getIsOnSolidGround().isOnSolidGround()) IOSG = false;
        if(((OverWorld) getWorld()).getCanMoveLeft().canMoveLeft()) CML = true;
        else if(!((OverWorld) getWorld()).getCanMoveLeft().canMoveLeft()) CML = false;
        if(((OverWorld) getWorld()).getCanMoveRight().canMoveRight()) CMR = true;
        else if(!((OverWorld) getWorld()).getCanMoveRight().canMoveRight()) CMR = false;
        
    }
    public void Move() {
        int y = getY();
        int x = getX();
        if(Greenfoot.isKeyDown("w") && !DBH) y += step;  
        if(Greenfoot.isKeyDown("s") && !IOSG) y -= step;
        if(Greenfoot.isKeyDown("a") && CML) x += step;  
        if(Greenfoot.isKeyDown("d") && CMR) x -= step;
        setLocation(x, y);
        
    }
    public Scenery(int width, int height) {
        GreenfootImage image = getImage();
        image.scale(width, height);
        setImage(image);
    }
    public void act() 
    {
        boolSet();
        Move();
    }    
}

My 'Platform' code is here:

import greenfoot.*;

public class Platform extends Actor
{
    private int step = 3;
    private boolean DBH = false;
    private boolean IOSG = false;
    private boolean CML = false;
    private boolean CMR = false;
    
    public void boolSet() {
        if(((OverWorld) getWorld()).getDidBumpHead().didBumpHead()) DBH = true;
        else if(!((OverWorld) getWorld()).getDidBumpHead().didBumpHead()) DBH = false;
        if(((OverWorld) getWorld()).getIsOnSolidGround().isOnSolidGround()) IOSG = true;
        else if(!((OverWorld) getWorld()).getIsOnSolidGround().isOnSolidGround()) IOSG = false;
        if(((OverWorld) getWorld()).getCanMoveLeft().canMoveLeft()) CML = true;
        else if(!((OverWorld) getWorld()).getCanMoveLeft().canMoveLeft()) CML = false;
        if(((OverWorld) getWorld()).getCanMoveRight().canMoveRight()) CMR = true;
        else if(!((OverWorld) getWorld()).getCanMoveRight().canMoveRight()) CMR = false;
    }
    public Platform() {
        this(100, 25);
    }
    
    public void Move() 
    {
        int y = getY();
        int x = getX();
        if(Greenfoot.isKeyDown("w") && !DBH) y += step;  
        if(Greenfoot.isKeyDown("s") && !IOSG) y -= step;
        if(Greenfoot.isKeyDown("a") && CML) x += step;  
        if(Greenfoot.isKeyDown("d") && CMR) x -= step;
        setLocation(x, y);
        
    }
    public Platform(int width, int height) {
        GreenfootImage image = getImage();
        image.scale(width, height);
        setImage(image);
    }
    public void act() 
    {
        boolSet();
        Move();
    }    
}

And finally my 'Jumper' code is here: (I commented out my old fall, jump and move methods as this game doesn't require them)

import greenfoot.*;

public class Jumper extends Actor
{
    private final int GRAVITY = 1;
    private final int STEP = 5;
    private int velocity;
    private int aniTimeD = 0;
    private int aniTimeA = 0;
    private int aniTimeW = 0;
    private int aniTimeS = 0;
    private int imageHeight = 100;
    private int imageWidth = 75;
    
     
     public Jumper() {
        this(75, 100);
        velocity = 0;
    }
    
    public Jumper(int width, int height) {
        GreenfootImage image = getImage();
        image.scale(width, height);
        setImage(image);
     }
    
    public void act() 
    {
        /**fall();
        if (Greenfoot.isKeyDown("space") && isOnSolidGround()) jump();
        move();**/
        if(aniTimeD == 19) aniTimeD = 0;
        if(aniTimeA == 19) aniTimeA = 0;
        if(aniTimeW == 19) aniTimeW = 0;
        if(aniTimeS == 19) aniTimeS = 0;
        GreenfootImage image = getImage();
        if (Greenfoot.isKeyDown("w") && !Greenfoot.isKeyDown("a") && !Greenfoot.isKeyDown("s") && !Greenfoot.isKeyDown("d") && !didBumpHead())
        {
            aniTimeW = aniTimeW + 1;
            if (aniTimeW == 1) setImage(new GreenfootImage("GuyBack.png"));
            if (aniTimeW == 7) setImage(new GreenfootImage("GuyBack2.png"));
            if (aniTimeW == 13) setImage(new GreenfootImage("GuyBack3.png"));
        }
        if (!Greenfoot.isKeyDown("w") && !Greenfoot.isKeyDown("a") && Greenfoot.isKeyDown("s") && !Greenfoot.isKeyDown("d") && !isOnSolidGround())
        {
            aniTimeD = aniTimeD + 1;
            if (aniTimeD == 1) setImage(new GreenfootImage("GuyFront.png"));
            if (aniTimeD == 7) setImage(new GreenfootImage("GuyFront2.png"));
            if (aniTimeD == 13) setImage(new GreenfootImage("GuyFront3.png"));
        }    
        
        if (!Greenfoot.isKeyDown("w") && !Greenfoot.isKeyDown("a") && !Greenfoot.isKeyDown("s") && Greenfoot.isKeyDown("d") && canMoveRight())
        {
            aniTimeD = aniTimeD + 1;
            if (aniTimeD == 1) setImage(new GreenfootImage("GuyRight.png"));
            if (aniTimeD == 7) setImage(new GreenfootImage("GuyRight2.png"));
            if (aniTimeD == 13) setImage(new GreenfootImage("GuyRight3.png"));
        }
        if (!Greenfoot.isKeyDown("w") && Greenfoot.isKeyDown("a") && !Greenfoot.isKeyDown("s") && !Greenfoot.isKeyDown("d") && canMoveLeft())
        {
            aniTimeA = aniTimeA + 1;
            if (aniTimeA == 1) setImage(new GreenfootImage("GuyLeft.png"));
            if (aniTimeA == 7) setImage(new GreenfootImage("GuyLeft2.png"));
            if (aniTimeA == 13) setImage(new GreenfootImage("GuyLeft3.png"));
            
        }
    }    
    
    /**public void fall() {
        setLocation(getX(), getY() + velocity);
        if (isOnSolidGround()) {
            velocity = 0;
            
            while (isOnSolidGround()) {
                setLocation(getX(), getY() - 1);
            }
            setLocation(getX(), getY() + 1);
        }
        else if (velocity < 0 && didBumpHead()) {
            velocity = 0;
            
            while (didBumpHead()) {
                setLocation(getX(), getY() + 1);
            }
        }
        else velocity += GRAVITY;
    }**/
    
    public void jump() {
        velocity = -20;
    }
       
    /**public void move() {
        int y = getY();
        int x = getX();
        if(Greenfoot.isKeyDown("a") && canMoveLeft()) x -= STEP;  
        if(Greenfoot.isKeyDown("d") && canMoveRight()) x += STEP;
        setLocation(x, y);
    }**/
    
    public boolean isOnSolidGround() {
        boolean isOnGround = false;
        
        if (getY() > getWorld().getHeight() - 50) isOnGround = true;
        
        int imageWidth = getImage().getWidth();
        int imageHeight = getImage().getHeight();
        if(getOneObjectAtOffset(imageWidth / -2, imageHeight / 2, Platform.class) != null ||
            getOneObjectAtOffset(imageWidth / 2, imageHeight / 2, Platform.class) != null) 
            isOnGround = true;
        
        return isOnGround;
    }
    
    public boolean didBumpHead() {
        boolean bumpedHead = false;
        
        int imageWidth = getImage().getWidth();
        int imageHeight = getImage().getHeight();
        if(getOneObjectAtOffset(imageWidth / -2, imageHeight / -2, Platform.class) != null ||
            getOneObjectAtOffset(imageWidth / 2, imageHeight / -2, Platform.class) != null) 
            bumpedHead = true;
            
        return bumpedHead;
    }
    public boolean canMoveLeft() {
        boolean canMoveLeft = true;
        
        int imageWidth = getImage().getWidth();
        int imageHeight = getImage().getHeight();
        if(getOneObjectAtOffset(imageWidth / -2 - STEP, imageHeight / -2, Platform.class) != null ||
            getOneObjectAtOffset(imageWidth / -2 - STEP, imageHeight / 2 - 1, Platform.class) != null) 
            canMoveLeft = false;
            
        return canMoveLeft;
    }
    
    public boolean canMoveRight() {
        boolean canMoveRight = true;
        
        int imageWidth = getImage().getWidth();
        int imageHeight = getImage().getHeight();
        if(getOneObjectAtOffset(imageWidth / 2 + STEP, imageHeight / -2, Platform.class) != null ||
            getOneObjectAtOffset(imageWidth / 2 + STEP, imageHeight / 2 - 1, Platform.class) != null) 
            canMoveRight = false;
            
        return canMoveRight;
    }
}

Lastly there's a video summarising it (feel free to pause): Click Here

danpost

2019/1/11

The_Beast0007 wrote...

when I try to run it the greenfoot terminal pops up and throws an exception

Remove the first word, "Jumper ", from line 26 in your OverWorld class code.

The_Beast0007

2019/1/11

!AAARGH!! IS IT REALLY THAT SIMPLE I HAD BEEN TRYING TO FIGURE IT OUT FOR OVER 3 HOURS!!!!!!! YAY! But thank you once again danpost for saving me when I was going to uninstall greenfoot.

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Moving Scenery NullPointerException