NullPointerException

En anden gang må du gerne poste hele dit stacktrace

Har du husket at oprette en instans af SpriteCache? Det kunne godt se ud til, at variablen spriteCache er null

Det her er et stacktrace ikk?
Exception in thread "main" java.lang.NullPointerException
at tankWars.Actor.paint(Actor.java:37)
at tankWars.TankWars.paintWorld(TankWars.java:71)
at tankWars.TankWars.game(TankWars.java:78)
at tankWars.TankWars.main(TankWars.java:92)

Vis jeg splitter spriteCache.getSprite(spriteName) op i flere linjer således:

SpriteCache.
getSprite(
spriteName);

er det den anden linje den siger fejlen er i, men jeg ved ikke om det har nogen betydnign.

spriteCache bliver først oprettet i klassen TankWars constructor:

spriteCache = new SpriteCache();

der bliver oprettet en instans of TankWars i main metoden. Main metoden ligger også i TankWars.

TankWars game = new TankWars();

i Actor objectet hvor metoden public void paint(Graphics2D) ligger bliver spriteCache initaliseret således:

public Actor(TankWars tw) {
		game = tw;
		spriteCache = game.getSpriteCache();
		frameSpeed = 1;
		currentFrame = 1;
		spriteName = "tankSheet.gif";
	}

TankWars.getSpriteCache() ser sådan her ud:

public SpriteCache getSpriteCache() {return spriteCache;}

Så for mig ser det ud som om spriteCache indeholder et SpriteCache objekt...

her er hele koden til spillet (fylder ikke så meget endu):

//TankWars
package tankWars;

import java.awt.*;
import java.awt.image.BufferStrategy;
import java.util.Iterator;
import java.util.Vector;

import javax.swing.JFrame;
import javax.swing.JPanel;

import game.KeyboardInput;

public class TankWars extends Canvas {
	public static final int PLAY_HEIGHT = 400;
	public static final int HEIGHT = 440;
	public static final int WIDTH = 600;
	public static final int SPEED = 10;
	
	private boolean done;
	
	private KeyboardInput keyboard;
	private Vector actors;
	private BufferStrategy strategy;
	private SpriteCache spriteCache;
	
	private Actor a1;
	
	public TankWars() {
		a1 = new Actor(this);
		a1.setXPos(3);
		a1.setYPos(3);
		a1.setSpriteName("tankSheet.gif");
		a1.setWidth(24);
		a1.setHeight(32);
		
		setBounds(0, 0, TankWars.WIDTH, TankWars.HEIGHT);
		
		JFrame vindue = new JFrame();
		vindue.setTitle("Tank Wars");
		vindue.setBounds(0, 0, TankWars.WIDTH, TankWars.HEIGHT);
		vindue.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		vindue.setResizable(false);
		
		JPanel panel = (JPanel)vindue.getContentPane();
		panel.setPreferredSize(new Dimension(TankWars.WIDTH, TankWars.HEIGHT));
		panel.setLayout(null);
		panel.add(this);
		
		this.setBackground(new Color(0, 255, 0));
		
		vindue.setVisible(true);
		
		done = false;
		keyboard = new KeyboardInput();
		actors = new Vector();
		spriteCache = new SpriteCache();
		createBufferStrategy(2);
		strategy = getBufferStrategy();
	}
	
	public void updateWorld() {
		for(Iterator i = actors.iterator(); i.hasNext();) {
			Actor a = (Actor)i.next();
			a.act();
		}
		a1.act();
	}
	
	public void paintWorld() {
		Graphics2D g = (Graphics2D)strategy.getDrawGraphics();
		a1.paint(g);
		strategy.show();
	}
	
	public void game() {
		while(!done) {
			updateWorld();
			paintWorld();
			try {
				Thread.sleep(SPEED);
			} 
			catch (InterruptedException e) {
				System.out.println(e + "");
			}
		}
	}
	
	public SpriteCache getSpriteCache() {return spriteCache;}
	
	public static void main(String[] args) {
		TankWars game = new TankWars();
		game.game();
	}
}

//SpriteCache
package tankWars;

import java.awt.image.BufferedImage;
import java.io.File;
import java.net.URL;
import java.util.HashMap;

import javax.imageio.ImageIO;

public class SpriteCache {
	private HashMap sprites;
	
	public SpriteCache() {
		sprites = new HashMap();
	}
	
	private BufferedImage loadImage(String image) {
		URL url=null;
		try {
			url = getClass().getResource(image);
			return ImageIO.read(url);
		} 
		catch (Exception e) {
			System.out.println(e);
			System.exit(0);
			return null;
		}
	}
	
	public BufferedImage getSprite(String image) {
		BufferedImage img = (BufferedImage)sprites.get(image);
		if(img == null) {
			img = loadImage("res\\" + image);
			sprites.put(image, img);
		}
		return img;
	}
}

//Actor
package spaceInvaders1;

import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;

public class Actor {
	protected int x, y;
	protected int width, height;
	protected String[] spriteNames;
	protected int currentFrame;
	protected Stage stage;
	protected SpriteCache spriteCache;
	protected int frameSpeed;
	protected int t;
	protected boolean markedForRemoval;
	
	
	public Actor(Stage stage) {
		this.stage = stage;
		spriteCache = stage.getSpriteCache();
		currentFrame = 0;
		frameSpeed = 1;
		t = 0;
	}
	
	public void act() {
		t++;
		
		if(t % frameSpeed == 0) {
			currentFrame = currentFrame + 1;
			if(currentFrame >= spriteNames.length) {
				currentFrame = 0;
			}
		}
	}
		
	public void paint(Graphics2D g) {
		g.drawImage(spriteCache.getSprite(spriteNames[currentFrame]), x, y, stage);
	}
	
	public void collision(Actor a) {}
	
	public void remove() {
		markedForRemoval = true;
	}
	
	public boolean isMarkedForRemoval() {
		return markedForRemoval;
	}
	
	public Rectangle getBounds() {
		return new Rectangle(x, y, height, width);
	}
	
	public int getX() {return x;}
	public void setX(int i) {x = i;}
	
	public int getY() {return y;}
	public void setY(int i) {y = i;}
	
	public int getFrameSpeed() {return frameSpeed;}
	public void setFrameSpeed(int i) {frameSpeed = i;}
	
	public int getWidth() {return width;}
	public void setWidth(int i) {width = i;}
	
	public int getHeight() {return height;}
	public void setHeight(int i) {height = i;}
	
	public void setSpriteNames(String[] names) {
		spriteNames = names;
		width = 0;
		height = 0;
		for(int i = 0; i < spriteNames.length; i++) {
			BufferedImage image = spriteCache.getSprite(spriteNames[i]);
				width = Math.max(width, image.getWidth());
				height = Math.max(height, image.getHeight());
		}
	}
}

har selv ordent det
jeg initaliserede først spriteCache efter jeg brugte get sprite til at fortælle min actor hvilke billeder han skulle have.

Nu er jeg så stødt ind i et nyt problem... men jeg tror godt jeg kan løse det selv

.:Edit:.
Og nu fik jeg så også løst det...

hvorfor bruger du ikke den typeparametriserede hashmap?
så kan du undgå (manuelt) at lave typecasts.

mvh
Troels

hvorfor bruger du ikke den typeparametriserede hashmap?
så kan du undgå (manuelt) at lave typecasts.

mvh
Troels

Fordi SpriteCache er næsten 100% kopieret fra en tutorial, og jeg ikke har tænkt på at lave det om endu.

Men tak fordi du mindede mig om det