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Tesseract42
Tesseract42 wrote ...

2016/1/11

Shooting a Laser

Tesseract42 Tesseract42

2016/1/11

#
I'm trying to make a game with a cat that shoots lasers. The cat is supposed to shoot a short laser segment when the spacebar is pressed that is created again and again until it hits a wall, then stops. I haven't yet written the code to make the laser disappear after it's shot, but I think it should still work. The game functions fine until the spacebar is pressed, then it freezes. I assume that I'm causing some kind of infinite loop where the laser doesn't realize that it hit a wall and keeps on going forever, but I can't figure out what's causing it. Can someone please help? LaserCat class:
?
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import greenfoot.*;
 
/**
 * Write a description of class LaserCat here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
 
 
public class LaserCat extends Actor
{
    private GreenfootImage Down1 = new GreenfootImage("KnightDog7.png");
    private GreenfootImage Down2 = new GreenfootImage("KnightDog8.png");
    private GreenfootImage Up1 = new GreenfootImage("KnightDog1.png");
    private GreenfootImage Up2 = new GreenfootImage("KnightDog2.png");
    private GreenfootImage Left1 = new GreenfootImage("KnightDog3.png");
    private GreenfootImage Left2 = new GreenfootImage("KnightDog4.png");
    private GreenfootImage Right1 = new GreenfootImage("KnightDog5.png");
    private GreenfootImage Right2 = new GreenfootImage("KnightDog6.png");
    private int animationSpeed = 10;
    private int frame = 1;
    private int direction;
    private int timer = 0;
    int catDirection = 2;
    public void act()
    {
        checkKey();
        checkFire();
    }   
    private int speed = 1;
    public void checkKey()
    {
        if (Greenfoot.isKeyDown("down"))
        {
            catDirection = 2;
            goDown();
        }
        if (Greenfoot.isKeyDown("up"))
        {
            catDirection = 1;
            goUp();
        }
        if (Greenfoot.isKeyDown("left"))
        {
            catDirection = 3;
            goLeft();
        }
        if (Greenfoot.isKeyDown("right"))
        {
            catDirection = 4;
            goRight();
        }
    }
    public void goDown()
    {
        timer++;
        setLocation(getX(),getY() + speed);
        if (frame == 1 && timer % 5 == 0)
        {
            setImage(Down1);
            frame = 2;
        }
        else if (frame == 2 && timer % 5 == 0)
        {
            setImage(Down2);
            frame = 1;
        }
    }
        public void goUp()
    {
        timer++;
        setLocation(getX(),getY() - speed);
        if (frame == 1 && timer % 5 == 0)
        {
            setImage(Up1);
            frame = 2;
        }
        else if (frame == 2 && timer % 5 == 0)
        {
            setImage(Up2);
            frame = 1;
        }
    }
        public void goRight()
    {
        timer++;
        setLocation(getX() + speed,getY());
        if (Greenfoot.isKeyDown("down") == false && Greenfoot.isKeyDown("left") == false && Greenfoot.isKeyDown("up") == false)
        {
            if (frame == 1 && timer % 5 == 0)
            {
                setImage(Right1);
                frame = 2;
            }
            else if (frame == 2 && timer % 5 == 0)
            {
                setImage(Right2);
                frame = 1;
            }
        }
    }
        public void goLeft()
    {
        timer++;
        setLocation(getX() - speed,getY());
        if (Greenfoot.isKeyDown("down") == false && Greenfoot.isKeyDown("right") == false && Greenfoot.isKeyDown("up") == false)
        {
            if (frame == 1 && timer % 5 == 0)
            {
                setImage(Left1);
                frame = 2;
            }
            else if (frame == 2 && timer % 5 == 0)
            {
                setImage(Left2);
                frame = 1;
            }
        }
    }
    public void checkFire()
    {
        if(Greenfoot.getKey() == "space")
        {
            shootLaser();
        }
    }
    public int getDirection()
    {
        return catDirection;
    }
    private int laserLength = 0;
    public void shootLaser()
    {
        while (Laser.noWallDetected == true)
        {
            getWorld().addObject(new Laser(this), getX(), getY() + laserLength);
            laserLength += 2;
        }
        laserLength = 0;
    }
}
Laser class:
?
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import greenfoot.*;
 
/**
 * Write a description of class Laser here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class Laser extends Actor
{
    private LaserCat myCat;
    private boolean checkedForWall = false;
    public static boolean noWallDetected = true;
    public Laser(LaserCat myCat)
    {
        this.myCat = myCat;
    }
    public void act()
    { 
        if (checkedForWall == false)
        {
            if (wallDetected())
                noWallDetected = false;
            else
                noWallDetected = true;
            checkedForWall = true;
        }
    }
    public boolean wallDetected()
    {
        Actor a = getOneIntersectingObject(Wall.class);
        if(this.isAtEdge() || a != null)
            return true;
        else
            return false;
    }
}
danpost danpost

2016/1/11

#
By using a 'while' loop in the LaserCat class, code execution stays in the 'shootLaser' method and does not allow the 'act' method of the Laser class to execute. This prevents the value of 'noWallDetected' to not have a chance to change; thereby, locking the exeecutiion within the loop. In greenfoot, code your objects for what they need to do during each instance in time -- not for what they need to do in the long run.
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