所以,首先这是我第一次发帖,我正在尝试用 java(1.8) 和 IntelliJ 制作一个自上而下的游戏,仅此而已。我的所有代码都已做好并已完成(用于显示精灵),我对其进行了测试,但它不断给我错误消息,指出某些部分无效。它应该在右上角的屏幕上显示一个图像(字符),这里是所有代码,请记住,我还没有完全完成:
游戏.java
package main;
import main$entities.Player;
import main$gfx.ImageLoader;
import main$gfx.SpriteSheet;
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.lang.*;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static final int WIDTH = 700, HEIGHT = 400, SCALE = 1;
public static boolean running = false;
public Thread gameThread;
private BufferedImage spriteSheet;
private Player player;
public void init(){
ImageLoader loader = new ImageLoader();
spriteSheet = loader.load("./spritesheet.png");
SpriteSheet ss = new SpriteSheet(spriteSheet);
player = new Player(0, 0, ss);
}
public synchronized void start(){
if(running)return;
running = true;
gameThread = new Thread(this);
gameThread.start();
}
public synchronized void stop(){
if(!running)return;
running = false;
try {
gameThread.join();
} catch (InterruptedException e) {e.printStackTrace();}
}
public void run(){
long lastTime = System.nanoTime();
final double amountOfTicks = 60D;
double ns = 1000000000 / amountOfTicks;
double delta = 0;
while(running){
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
if(delta >= 1){
tick();
delta--;
}
render();
}
stop();
}
public void tick(){
player.tick();
}
public void render(){
BufferStrategy bs = this.getBufferStrategy();
if(bs == null){
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
// Render Here
g.fillRect(0, 0, WIDTH * SCALE, HEIGHT * SCALE);
player.render(g);
// End Render
g.dispose();
bs.show();
}
public static void main(String[] args){
Game game = new Game();
game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
JFrame frame = new JFrame("Tile RPG");
frame.setSize(WIDTH *SCALE, HEIGHT * SCALE);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.add(game);
frame.setVisible(true);
game.start();
}
}
ImageLoader.java
package main$gfx;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
public class ImageLoader {
public BufferedImage load(String path){
try {
return ImageIO.read(getClass().getResource(path));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
SpriteSheet.java
package main$gfx;
import java.awt.image.BufferedImage;
public class SpriteSheet {
private BufferedImage sheet;
public SpriteSheet(BufferedImage sheet){
this.sheet = sheet;
}
public BufferedImage crop(int col, int row, int w, int h){
return sheet.getSubimage(col * 16, row * 16, w, h);
}
}
播放器.java
package main$entities;
import main.Game;
import main$gfx.SpriteSheet;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class Player implements KeyListener{
private int x, y;
private SpriteSheet ss;
private boolean up = false, dn = false, lt = false, rt = false;
private final int SPEED = 3;
public Player(int x, int y, SpriteSheet ss){
this.x = x;
this.y = y;
this.ss = ss;
}
public void tick(){
if(up){
y -= SPEED;
}
if(dn){
y += SPEED;
}
if(lt){
x -= SPEED;
}
if(rt){
x += SPEED;
}
}
public void render(Graphics g){
g.drawImage(ss.crop(0 ,0, 16, 16), x, y, 16 * Game.SCALE, 16 * Game.SCALE, null);
}
public void keyTyped(KeyEvent e) {}
public void keyPressed(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
}
错误消息(它给了我多条消息,每次都不一样 // = 那一行是什么,所以你不必通过计数找到它,欢迎您):
我第一次运行 Game.java:
Exception in thread "Thread-2" java.lang.NullPointerException
at main.Game.tick(Game.java:64) // player.tick();
at main.Game.run(Game.java:56) // tick();
at java.lang.Thread.run(Thread.java:745) // this is in the JDK itself
Process finished with exit code 0
我运行 Game.java 的第二次(以及所有这些)时间:
Exception in thread "Thread-2" java.lang.NullPointerException
at main.Game.render(Game.java:77) // player.render(g);
at main.Game.run(Game.java:59) // render();
at java.lang.Thread.run(Thread.java:745) // this is in the JDK itself
Process finished with exit code 0