java - Java 游戏中不显示背景图像

Question

这是我之前的一个问题的后续问题。我正在制作一个java游戏，它基本上是一个带有角色图像的JFrame，一些由fillRect()组成的健康栏，它们都位于背景图像的顶部。问题是生命条和角色出现了，但背景图像没有出现。

这是 Game 类的简化版本，其中包含 main() 和 render() 方法:

public class Game extends Canvas implements Runnable{

    public static boolean running = false;
    public Thread gameThread;

    private BufferedImage playerSpriteSheet;
    private ImageManager im;

    private static Player player;
    private static HealthBar healthBars;
    private static BackgroundImage backgroundImage;

    public void init(){
        ImageLoader loader = new ImageLoader();
        playerSpriteSheet = loader.load("/spriteSheet.png");
        SpriteSheet pss = new SpriteSheet(playerSpriteSheet);

        im = new ImageManager(pss);

        backgroundImage = new BackgroundImage("/background.png");
        player = new Player(800, 250, im);
        healthBars = new HealthBar(200, 200);

        this.addKeyListener(new KeyManager());
    }

    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) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void run() {
        init();
        long lastTime = System.nanoTime();
        final double amountOfTicks = 60D;
        double ns = 1_000_000_000/amountOfTicks;
        double delta = 0;
        long now = System.nanoTime();

        while(running)
        {
            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); //Use 5 at most
            return;
        }
        Graphics g = bs.getDrawGraphics();

        //RENDER HERE
        backgroundImage.render(g);
        player.render(g);
        healthBars.render(g);


        //END RENDER
        g.dispose();
        bs.show();
    }

    public static void main(String[] args)
    {
        JLabel backgroundImage;
        JLabel controlKeyPanel;
        JLabel statusLabel;

        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("Title");
        frame.setResizable(false);
        frame.setSize(WIDTH * SCALE, HEIGHT * SCALE);
        frame.setLayout(new BorderLayout());

        backgroundImage = new JLabel(new ImageIcon("/background.png"));

        String htmlButtonGuide = "words";
        controlKeyPanel = new JLabel(htmlButtonGuide);

        statusLabel = new JLabel("label");


        frame.add(backgroundImage, BorderLayout.CENTER);
        frame.add(controlKeyPanel, BorderLayout.EAST);
        frame.add(statusLabel, BorderLayout.SOUTH);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(game);

        frame.setVisible(true);

        game.start();
        //Program seems to continue running after ESC
    }

    public static Player getPlayer() {
        return player;
    }

}

这是 BackGroundImage 类:

public class BackgroundImage {

    private Image background = null;


    public BackgroundImage(String s) {
        if(s == null)
        {
            background = getImage(s);
        }
    }

    public void render(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        g2.drawImage(background, 0, 0, 1200, 600, null);
    }

    public Image getImage(String path) {

        Image tempImage = null;

        File image2 = new File(path);
        try {
            tempImage = ImageIO.read(image2);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return tempImage;
    }
}

我关心 render() 方法重用“g”Graphics 对象将所有 3 个东西添加到屏幕上。有人告诉我不要将轻量级的 Swing 生命值条与厚重的 AWT 背景和角色结合起来？谁能指出我正确的方向来显示背景？渲染方法是否应该不考虑背景？我只需要把背景放一次。它不需要像生命条和角色那样不断更新，对吗？

Answer 1

让我们从...开始

backgroundImage = new BackgroundImage("/background.png");

这变成了...

File image2 = new File(path);

或

File image2 = new File("/background.png");

所以你可以看到它...你能看出这个有问题吗？这是请求一个位于当前驱动器根位置的文件...这并不是我认为您想要的...

The images are stored in a folder called "res" in the main project folder

这表明您想要使用...

backgroundImage = new BackgroundImage("res/background.png");

假设图像不是嵌入资源......

下一步...

public BackgroundImage(String s) {
    if (s == null) {
        background = getImage(s);
    }
}

因此，您只想在引用为 null 时尝试加载图像？？？

旁注...

frame.setSize(WIDTH * SCALE, HEIGHT * SCALE); 是一个坏主意，因为框架的边框占据了框架本身内部的空间。

最好重写 Canvas 的 getPreferredSize 方法并提供您要使用的默认大小值，然后在框架上调用 pack 。这将计算框架的大小作为其内容的首选大小加上框架边框要求...

你的“游戏循环”正在疯狂运行......

while (running) {
    delta += (now - lastTime) / ns;
    lastTime = now;
    if (delta >= 1) {
        tick();
        delta--;
    }
    render();
}

基本上，这将尽可能快地运行，并将减少其他线程运行的机会，最终使您的游戏(可能还有您的电脑)崩溃

这是运行循环的“简单”概念......

public void run() {
    init();
    final long amountOfTicks = 60;
    long ns = Math.round(1_000_000_000 / (double)amountOfTicks);

    int frames = 0;
    long frameStart = System.currentTimeMillis();

    while (running) {
        long startedAt = System.nanoTime();
        tick();
        render();
        long completedAt = System.nanoTime();
        long duration = completedAt - startedAt;

        long frameEnd = System.currentTimeMillis();
        if (frameEnd - frameStart >= 1000) {
            System.out.println(frames);
            frames = 0;
            frameStart = System.currentTimeMillis();
        } else {
            frames++;
        }

        long rest = ns - duration;
        if (rest > 0) {
            rest = TimeUnit.MILLISECONDS.convert(rest, TimeUnit.NANOSECONDS);
            try {
                Thread.sleep(rest);
            } catch (InterruptedException ex) {
            }
        }
    }
    stop();
}

基本上，它会尝试确保每次迭代之间有足够的延迟，以维持您试图达到的 60fps 目标...而不会让系统挨饿...