Question

我正在制作一个程序，特定的游戏，所以我从基本的东西开始，但是当我尝试测试它时，它会删除代码中没有出现的奇怪错误，所以我想我的代码很好，但是我不知道是什么原因引起的。：（

这是错误：

Exception in thread "main" java.lang.NullPointerException
    at java.awt.image.BufferedImage.<init>(Unknown Source)
    at ca.hawk.game.Game.<init>(Game.java:33)
    at ca.hawk.game.Game.main(Game.java:126)

这是代码（包）：

package ca.hawk.game;

import java.awt.BorderLayout;
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 java.awt.image.IndexColorModel;

import javax.swing.JFrame;

public class Game extends Canvas implements Runnable{

    private static final long serialVersionUID = 1L;

    public static final int WIDTH = 160;
    public static final int HEIGHT = WIDTH / 12 * 9;
    public static final int SCALE = 3;
    public static final String NAME = "Game";

    private static final int BufferedImage = 0;

    private static final IndexColorModel TYPE_INT_RGB = null;

    private JFrame frame;

    public boolean running = false;
    public int tickCount = 0;

    private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage, TYPE_INT_RGB);
    private int[] pixels = ((DataBufferInt) image.getRaster().getDataBuffer()).getData();

    public Game(){
        setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
        setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
        setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));

        frame = new JFrame(NAME);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());

        frame.add(this, BorderLayout.CENTER);
        frame.pack();

        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public synchronized void start() {
        running = true;
        new Thread(this).start();
    }

    private synchronized void stop(){
        running = false;
    }

    public void run() { 
        long lastTime = System.nanoTime();
        double nsPerTick = 1000000000D/60D;

        int ticks = 0;
        int frames = 0;

        long lastTimer = System.currentTimeMillis();
        double delta = 0;
        while (running){
            long now = System.nanoTime();
            delta += (now - lastTime) / nsPerTick;
            lastTime = now;
            boolean shouldRender = true;

            while (delta >= 1){
                ticks++;
                tick();
                delta -= 1;
                shouldRender = true;
            }
            try {
                Thread.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            if (shouldRender){
                frames++;
                render();
            }

            if (System.currentTimeMillis() - lastTimer > 1000){
                lastTimer += 1000;
                System.out.println(frames +", "+ ticks);
                frames = 0;
                ticks = 0;
            }
        }
    }

    public void tick(){
        tickCount++;
    }

    public void render(){
        BufferStrategy bs = getBufferStrategy();
        if (bs == null){
            createBufferStrategy(3);
            return;
        }

        Graphics g = bs.getDrawGraphics();

        g.setColor(Color.BLACK);
        g.fillRect(0, 0, getWidth(), getHeight());

        g.drawImage(image, 0, 0, getWidth(), getHeight(), null);

        g.dispose();
        bs.show();
    }

    public static void main(String[] args){
        new Game().start();
    }
}

Answer 1

改变：

private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage, TYPE_INT_RGB);

为：

private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage, BufferedImage.TYPE_INT_ARGB);

您设置的变量TYPE_INT_RGB为null，因此当您创建缓冲图像时，它会抛出空指针异常。

TYPE_INT_RGB是public static final上的BufferedImage变量。 Public表示您可以在object中访问它，static表示其class变量不是object变量而final表示其始终为{}相同的值，例如，如果它的10将始终为10.

BufferedImage.TYPE_INT_RGB您可以访问它。

Java - Eclipse IDE，程序由指针异常错误终止

1 个答案: