我正在使用自定义像素引擎制作一个 rpg，当我尝试运行它时，我只得到一个 NullPointerException 并且我知道原因，但是当我尝试初始化该变量时，我在不同的位置得到另一个变量并修复了它现在它根本不会运行，我仍然得到一个 NullPointerException。这是出现错误的类，控制台告诉我错误出现在 screen.render(); 行。
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import sprites.SpriteSheetLoader;
public class Game extends Canvas implements Runnable{
private static final long serialVersionUID = 1L;
public static final int HEIGHT = 120;
public static final int WIDTH = 120;
public static final int SCALE = 3;
public static final String NAME = "TypicalRPG";
public SpriteSheetLoader loader;
private BufferedImage img = new BufferedImage(WIDTH * SCALE, HEIGHT * SCALE, BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt) img.getRaster().getDataBuffer()).getData();
private boolean running = false;
private Screen screen = new Screen(WIDTH, HEIGHT, loader);
Random random = new Random();
public void start(){
running = true;
new Thread(this).start();
}
public static void main(String args[]){
Game game = new Game();
game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
JFrame jf = new JFrame(NAME);
jf.add(game);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.pack();
jf.setVisible(true);
jf.setResizable(true);
game.start();
}
public void run(){
while(running){
tick();
render();
try{
Thread.sleep(5);
}
catch(InterruptedException e){ e.printStackTrace(); }
}
}
public void stop(){ running = false; }
public void tick(){
screen.render(0, 0, 0, 16, 16);
}
public void render(){
BufferStrategy bs = getBufferStrategy();
if(bs == null){
createBufferStrategy(3);
requestFocus();
return;
}
for(int i = 0; i < screen.pixels.length; i++){
pixels[i] = screen.pixels[i];
}
Graphics g = bs.getDrawGraphics();
g.drawImage(img, 0, 0, getWidth(), getHeight(), null);
g.dispose();
bs.show();
}
public void init(){
BufferedImage sheet = null;
try {
sheet = ImageIO.read(Game.class.getResourceAsStream("res/tiles.png"));
}
catch (IOException e) {
e.printStackTrace();
}
loader = new SpriteSheetLoader(sheet);
screen = new Screen(WIDTH, HEIGHT, loader);
}
}
这是具有 render() 的类：
import sprites.SpriteSheetLoader;
public class Screen{
public int[] pixels;
private SpriteSheetLoader loader;
private int w, h;
int xoff = 0, yoff = 0;
public Screen(int w, int h, SpriteSheetLoader loader){
this.loader = loader;
this.w = w;
this.h = h;
pixels = new int[w * h];
}
public void render(int xpos, int ypos, int tile, int width, int height){
loader.grabTile(tile, width, height);
xpos -= xoff;
ypos -= yoff;
for(int y = 0; y < height; y++){
if(ypos + y < 0 || ypos + y >= h) continue;
for(int x = 0; x < width; x++){
if(xpos + x < 0 || xpos + x >= w) continue;
int col = loader.pixels[x + (y * height)];
if(col != -65281) pixels[(x + xpos) + (y + ypos)] = col;
}
}
}
}