[SOLVED] Loading .gif images - url = null trouble

Newbie & Debugging Questions
#1

Hello all!

[quote]Oh…
Another quick question:

Am I referencing the images correctly? Am I supposed to start the reference as if I’m in the src (“sprites/alien.gif”) folder or somewhere else (in which case, where)?
I can’t reference any of the gifs (getting the fail msg I’ve implemented) Sad

ref = “sprites/homer.gif”

but when it gets to assigning URL, url = null
-_-
[/quote]
I am thoroughly annoyed with my current problem. I’m attempting to load an image and display it on screen (simple, huh?), but I can’t figure out what I’m doing wrong. To explain the code real quick - Screen class creates a JFrame and initiates everything. Sprite class is a wrapper for Image, contains a reference to an Image, a constructor and a draw method. SpriteStore is a singleton class for managing Sprite - mainly, I don’t want to load the same Sprite (Image) more than once. Thus - each unique sprite is stored in a HashMap (hashing is done according to the reference), upon requesting a Sprite, the HashMap is checked first. If the Sprite is already is the HashMap, I return the Sprite, otherwise, I load the sprite via the reference, store it in the HashMap and return it. Pretty simple and well understood.

Then, I decide to test it out, and load a random (.gif) image and draw it anywhere on the JFrame. The code breaks at:

Sprite testSprite = spriteStore.getSprite("sprites/homer2.gif");

at the screen init. The error is:

Exception in thread "main" java.lang.NullPointerException
	at Screen.<init>(Screen.java:17)
	at Screen.main(Screen.java:70)

I have no idea whats going on. The sprites/homer2.gif is located in my src folder. (I’m using Eclipse, if its relevant)

Here are three simple test classes:

import java.awt.Canvas;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Dimension;
import java.awt.image.BufferStrategy;
import java.awt.Graphics2D;
import java.awt.Color;

public class Screen extends Canvas {
	private BufferStrategy strategy;
	private JFrame frame;
	private JPanel mainPanel;
	private boolean working;
	private SpriteStore spriteStore = SpriteStore.get();
	
	
	Sprite testSprite = spriteStore.getSprite("sprites/homer2.gif");	
	
	private Screen() {
		frame = new JFrame("Accelerated Graphics Testing");		
		mainPanel = (JPanel)frame.getContentPane();
		mainPanel.setPreferredSize(new Dimension(800,600));
		mainPanel.setLayout(null);
		
		this.setBounds(0, 0, 800, 600);
		mainPanel.add(this);
		
		frame.pack();
		frame.setResizable(false);
		frame.setVisible(true);
		
		this.createBufferStrategy(2);
		strategy = this.getBufferStrategy();
		
		//initEntity();
		working = true;
		
		runningLoop();
	}

	/*private void initiateTestSprite(String ref) {
		testSprite = spriteStore.getSprite(ref);
	}*/
	
	private void runningLoop() {
		long lastLoopTime = System.currentTimeMillis(), delta;
		//initiateTestSprite("sprites/alien.gif");
		while(working) {
			delta = System.currentTimeMillis() - lastLoopTime;
			lastLoopTime = System.currentTimeMillis();
			
			Graphics2D g = (Graphics2D)strategy.getDrawGraphics();
			g.setColor(Color.CYAN);
			g.fillRect(0, 0, 800, 600);
			//
			testSprite.draw(g, 400, 200);
			//
			g.dispose();
			
			strategy.show();
			
			try {
				Thread.sleep(500);
			} catch(InterruptedException e) {}
			
		}
	}
	
	public static void main(String[] args) {
		new Screen();
	}
}


import java.awt.Graphics;
import java.awt.Image;

public class Sprite {
	private Image image;
	
	public Sprite(Image image) {
		this.image = image;
	}
	
	public int getWidth() {
		return image.getWidth(null);
	}
	
	public int getHeight() {
		return image.getHeight(null);
	}
	
	public void draw(Graphics g, int x, int y) {
		g.drawImage(image, x, y, null);
	}
	
}


import java.util.HashMap;
import java.awt.GraphicsEnvironment;
import java.awt.image.BufferedImage;
import java.net.URL;
import java.awt.GraphicsConfiguration;
import java.awt.Transparency;
import java.awt.Image;
import java.io.IOException;

import javax.imageio.ImageIO;

public class SpriteStore {
	// singleton logic
	private static SpriteStore single;
	
	public static SpriteStore get() {
		return single;
	}
	
	// 
	
	private HashMap sprites = new HashMap();
	
	public Sprite getSprite(String ref) {
		// if referenced .gif is loaded, return according sprite 
		if(sprites.get(ref) != null)
			return (Sprite)sprites.get(ref);
		
		// otherwise, load the referenced sprite, insert it into the HashMap and return the newly inserted sprite
		BufferedImage sourceImage = null;
		try {
			URL url = this.getClass().getClassLoader().getResource(ref);
			if(url == null)
				fail("Can't find that :( " + ref);
			sourceImage = ImageIO.read(url);			
		} catch(IOException e) {
			fail("Failed to load :( " + ref);
		}
		
		// accelerated graphics memory allocation
		GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
		Image image = gc.createCompatibleImage(sourceImage.getWidth(), sourceImage.getHeight(), Transparency.BITMASK);
		
		image.getGraphics().drawImage(sourceImage,0,0,null);
		
		Sprite sprite = new Sprite(image);
		sprites.put(ref, sprite);
		
		return sprite;
	}
	
	private void fail(String msg) {
		System.err.println(msg);
		System.exit(0);
	}
	
	
	
}

In case it’s relevant, I was following this tutorial.

Thanks in advance,
Regards :slight_smile: