我在 Java 游戏上的第一次尝试在我阅读图像时以 7 fps 的速度结束

Question

最近我一直在尝试用我在CS课上获得的知识来构建一个小游戏（2d，没什么大不了的）。在阅读了大约 2 周的那些图形相关类的文档后，我最终遇到了这种情况：我有一个正在运行的系统，以每秒 60 次游戏逻辑更新/每秒 60 帧的速度运行（:D，这个运行得很好）。作为第一个小测试，我想让图像在屏幕上移动。这是代码（部分是我的，部分来自一些教程）：

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.io.File;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class Game extends Canvas implements Runnable{
private static final long serialVersionUID = 1L;
public static final String NAME= "PokeCraft PRE-ALPHA";
public static final int HEIGHT=720;
public static final int WIDTH=HEIGHT*16/9;
public static final int SCALE=1;
private int fps=0;
private int tps=0;

private boolean running;
private int tickCount;
public void start(){
    running = true;
    new Thread(this).start();
}
public void stop(){
    running = false;
}
public void render(){
    BufferStrategy bufferStrategy =getBufferStrategy();
    if(bufferStrategy==null){
        this.createBufferStrategy(3);
        return;
    }
    /* render function */
      Graphics g = (Graphics) bufferStrategy.getDrawGraphics();
      g.clearRect(0, 0, super.getWidth(), super.getHeight());
      Image img = null;
      try{
          String imgPath = "data/MF.png";
          img = ImageIO.read(getClass().getResourceAsStream(imgPath));

      } catch(Exception e){
          System.out.println(e);
      }

        g.drawImage(img, tickCount, 0, null);
        Font font = new Font("Verdana",0,11);
        g.setFont(font);
        g.setColor(Color.RED);
        g.drawString(NAME+" / "+fps+" fps, "+tps+"tps", 5, 15);
      g.dispose();
      bufferStrategy.show();
}

public void run() {
    long lastTime= System.nanoTime();
    double unprocessed = 0;
    double nsPerTick = 1000000000.0/60.0;
    int frames = 0;
    int ticks = 0;
    long lastTimer1 = System.currentTimeMillis();
    while(running){
        long now = System.nanoTime();
        unprocessed += (now-lastTime)/nsPerTick;
        lastTime= now;
        boolean shouldRender= false;
        while(unprocessed >= 1){
            ticks++;
            tick();
            unprocessed -= 1;
            shouldRender = true;
        }
        if(shouldRender){
        frames++;
        render();
        }
        if(System.currentTimeMillis()-lastTimer1 > 1000){
            lastTimer1 += 1000;
            System.out.println(ticks+" ticks, "+frames + " fps");
            fps=frames;
            tps=ticks;
            ticks = 0;
            frames = 0;
        }
    }
}

public void tick(){
    tickCount++;
}
public static void main(String[] args){
    Game game= new Game();
    game.setPreferredSize(new Dimension(WIDTH*SCALE, HEIGHT*SCALE));
    game.setMinimumSize(new Dimension(WIDTH*SCALE, HEIGHT*SCALE));
    game.setMaximumSize(new Dimension(WIDTH*SCALE, HEIGHT*SCALE));

    JFrame frame = new JFrame(Game.NAME);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new BorderLayout());
    frame.add(game);
    frame.pack();
    frame.setResizable(true);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    game.start();
    }
}

ImageIO.read（...）确实对性能造成了很大的冲击（根据VisualVM，每次运行需要~200ms）。我该如何解决这个问题？

Answer 1

读取图像本身是一项成本高昂的操作。

因此，您应该在启动游戏时读取一次图像，并将其保存在内存中以便稍后访问。

Answer 2

避免在每次渲染图像时加载图像。使其成为类变量并仅加载一次。喜欢这个：

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.io.File;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Game extends Canvas implements Runnable {
    private static final long serialVersionUID = 1L;
    public static final String NAME = "PokeCraft PRE-ALPHA";
    public static final int HEIGHT = 720;
    public static final int WIDTH = HEIGHT * 16 / 9;
    public static final int SCALE = 1;
    private int fps = 0;
    private int tps = 0;
    private Image img = null;
    private boolean running;
    private int tickCount;
    public void start() {
        running = true;
        new Thread(this).start();
    }
    public void stop() {
        running = false;
    }
    public void render() {
        BufferStrategy bufferStrategy = getBufferStrategy();
        if (bufferStrategy == null) {
            this.createBufferStrategy(3);
            return;
        }
        /* render function */
        Graphics g = (Graphics) bufferStrategy.getDrawGraphics();
        g.clearRect(0, 0, super.getWidth(), super.getHeight());
        if (img == null) {
            try {
                String imgPath = "data/MF.png";
                img = ImageIO.read(getClass().getResourceAsStream(imgPath));
            } catch (Exception e) {
                System.out.println(e);
            }
        }
        g.drawImage(img, tickCount, 0, null);
        Font font = new Font("Verdana", 0, 11);
        g.setFont(font);
        g.setColor(Color.RED);
        g.drawString(NAME + " / " + fps + " fps, " + tps + "tps", 5, 15);
        g.dispose();
        bufferStrategy.show();
    }
    public void run() {
        long lastTime = System.nanoTime();
        double unprocessed = 0;
        double nsPerTick = 1000000000.0 / 60.0;
        int frames = 0;
        int ticks = 0;
        long lastTimer1 = System.currentTimeMillis();
        while (running) {
            long now = System.nanoTime();
            unprocessed += (now - lastTime) / nsPerTick;
            lastTime = now;
            boolean shouldRender = false;
            while (unprocessed >= 1) {
                ticks++;
                tick();
                unprocessed -= 1;
                shouldRender = true;
            }
            if (shouldRender) {
                frames++;
                render();
            }
            if (System.currentTimeMillis() - lastTimer1 > 1000) {
                lastTimer1 += 1000;
                System.out.println(ticks + " ticks, " + frames + " fps");
                fps = frames;
                tps = ticks;
                ticks = 0;
                frames = 0;
            }
        }
    }
    public void tick() {
        tickCount++;
    }
    public static void main(String[] args) {
        Game game = new Game();
        game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
        game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
        game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
        JFrame frame = new JFrame(Game.NAME);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(game);
        frame.pack();
        frame.setResizable(true);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        game.start();
    }
}

字体也是如此，尽管这可能不像图像加载那样影响性能。

Answer 3

磁盘操作非常慢，并且不需要每个循环访问文件，而这正是您当前正在执行的操作。使 img 变量成为类变量，并在 run（） 方法中进入 while（running） 循环之前对其进行实例化。