我正在关注来自ChernoProject的教程，但是在第22集中，我一直在尝试从精灵渲染像素数组时得到nullPointerException？
错误：
Exception in thread "Game" java.lang.ExceptionInInitializerError
at com.santec.game.learning.thecherno.graphics.Screen.render(Screen.java:40)
at com.santec.game.learning.thecherno.Game.render(Game.java:109)
at com.santec.game.learning.thecherno.Game.run(Game.java:78)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at com.santec.game.learning.thecherno.graphics.Sprite.load(Sprite.java:23)
at com.santec.game.learning.thecherno.graphics.Sprite.<init>(Sprite.java:17)
at com.santec.game.learning.thecherno.graphics.Sprite.<clinit>(Sprite.java:10)
... 4 more
课程：
Game.java：
package com.santec.game.learning.thecherno;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
import com.santec.game.learning.thecherno.graphics.Screen;
import com.santec.game.learning.thecherno.input.Keyboard;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static int width = 300;
public static int height = width / 16 * 9;
public static int scale = 3;
public static String title = "Rain";
private Thread thread;
private JFrame frame;
private boolean running = false;
private Screen screen;
private Keyboard key;
private BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
public Game() {
Dimension size = new Dimension(width * scale, height * scale);
setPreferredSize(size);
screen = new Screen(width, height);
frame = new JFrame();
key = new Keyboard();
addKeyListener(key);
}
public synchronized void start() {
running = true;
thread = new Thread(this, "Game");
thread.start();
}
public synchronized void stop() {
running = false;
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void run() {
long lastTime = System.nanoTime();
long timer = System.currentTimeMillis();
final double ns = 1000000000.0 / 60.0;
double delta = 0;
int frames = 0;
int updates = 0;
while(running) {
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
while(delta >= 1) {
update();
updates++;
delta--;
}
render();
frames++;
if(System.currentTimeMillis() - timer > 1000) {
timer += 1000;
frame.setTitle(title + ": " + updates + " ups | " + frames + " fps");
updates = 0;
frames = 0;
}
}
stop();
}
int x = 0, y = 0;
public void update() {
key.update();
if(key.up) y--;
if(key.down) y++;
if(key.right) x++;
if(key.left) x--;
}
public void render() {
BufferStrategy bs = getBufferStrategy();
if(bs == null) {
createBufferStrategy(3);
return;
}
screen.clear();
screen.render(x, y);
for(int i = 0; i < pixels.length; i++) {
pixels[i] = screen.pixels[i];
}
Graphics g = bs.getDrawGraphics();
{
g.setColor(Color.cyan);
g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
}
g.dispose();
bs.show();
}
public static void main(String[] args) {
Game game = new Game();
game.frame.setResizable(false);
game.frame.setTitle(game.title);
game.frame.add(game);
game.frame.pack();
game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
game.frame.setLocationRelativeTo(null);
game.frame.setVisible(true);
game.start();
}
}
graphics / SpriteSheet.java：
package com.santec.game.learning.thecherno.graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
public class SpriteSheet {
private String path;
public final int SIZE;
public int[] pixels;
// Spritesheets
public static SpriteSheet terrain = new SpriteSheet("/textures/terrain.png", 96);
public SpriteSheet(String path, int size) {
this.path = path;
SIZE = size;
pixels = new int[SIZE * SIZE];
load();
}
private void load() {
try {
BufferedImage image = ImageIO.read(SpriteSheet.class.getResource(path));
int w = image.getWidth();
int h = image.getHeight();
image.getRGB(0, 0, w, h, pixels, 0, w);
} catch (IOException e) {
e.printStackTrace();
}
}
}
graphics / Screen.java：
package com.santec.game.learning.thecherno.graphics;
import java.util.Random;
public class Screen {
private int width, height;
public int[] pixels;
public final int MAP_SIZE = 8;
public final int MAP_SIZE_MASK = MAP_SIZE - 1;
public int[] tiles = new int[MAP_SIZE * MAP_SIZE];
private Random random = new Random();
public Screen(int width, int height) {
this.width = width;
this.height = height;
pixels = new int[width * height];
for(int i = 0; i < MAP_SIZE * MAP_SIZE; i++) {
tiles[i] = random.nextInt(0xffffff);
tiles[0] = 0;
}
}
public void clear() {
for(int i = 0; i < pixels.length; i++) {
pixels[i] = 0;
}
}
public void render(int xOffset, int yOffset) {
for(int y = 0; y < height; y++) {
int yy = y + yOffset;
if(yy >= height || yy < 0) break;
for(int x = 0; x < width; x++) {
int xx = x + xOffset;
if(xx >= width || xx < 0) break;
int tileIndex = ((xx >> 4) & MAP_SIZE_MASK) + ((yy >> 4) & MAP_SIZE_MASK) * 8;
pixels[x + y * width] = Sprite.grass.pixels[(xx & 15) + (yy & 15) * Sprite.grass.SIZE];
}
}
}
}
graphics / Sprite.java：
package com.santec.game.learning.thecherno.graphics;
public class Sprite {
public final int SIZE;
private int x, y;
public int[] pixels;
private SpriteSheet sheet;
public static Sprite grass = new Sprite(16, 0, 1, SpriteSheet.terrain);
public Sprite(int size, int x, int y, SpriteSheet sheet) {
SIZE = size;
this.x = x * size;
this.y = y * size;
this.sheet = sheet;
load();
}
private void load() {
for(int y = 0; y < SIZE; y++) {
for(int x = 0; x < SIZE; x++) {
pixels[x + y * SIZE] = sheet.pixels[(x + this.x) + (y + this.y) * sheet.SIZE];
}
}
}
}
答案 0 :(得分：1)
您永远不会初始化pixels数组。
添加
this.pixels = new int[SIZE*SIZE]; // assuming that's the desired length or that array
到load方法的开头。