Java渲染循环和逻辑循环

Question

我一直在开发一款通用的 2d 瓷砖风格游戏。目前在我的主线程中，我有一个尽可能快的循环，并调用另一个处理游戏内容的类中的 JPanel 的重绘方法。它看起来像这样：

public class Main {
    public static void main(String[] args) {
        Island test = new Island();
        while(true) {
            test.getCanvas().requestFocus();
            test.getCanvas().repaint();
        }
    }
}

getCanvas() 只返回 JPanel。

目前这已经完成了我想要的，现在我已经开始为一名球员添加移动，显然我不想尽可能快地让他在屏幕上移动。所以我的 Island 类中有一个输入图和动作图，它检测按键的按下和释放，并告诉我的玩家类正在持有哪些键。然后，我使用每 10 毫秒调用一次的挥杆计时器在玩家类中移动我的玩家。所以我想这就像我的游戏滴答声，我的游戏将尽可能快地制作帧，然后游戏每秒执行 100 次所有逻辑内容，我当然会在游戏逻辑中添加更多内容，而不仅仅是运动。

在做了一些研究之后，似乎摇摆计时器并不是最好的方法，因为它是为执行小任务和摇摆任务而设计的。所以我想我的问题是，按照我的主要方法制作我的帧是否明智，以及让我的游戏每 10 毫秒可靠地运行一次的好方法是什么？我有一些想法，比如也许我应该创建一个新线程来处理游戏逻辑并使用 System.getnanotime 或任何它调用的东西来测量做一个滴答所需的时间，然后做一个小线程.sleep很长，直到我们达到 10 毫秒，然后重复。

如果您愿意，我很乐意发布更多代码 :)，提前致谢。

Answer 1

执行此操作的标准方法是在线程中。这是一个标准的游戏准系统游戏线程

public class GameThread implements Runnable {
    private Thread runThread;
    private boolean running = false;
    private boolean paused = false;
    public GameThread() {
    }

    public void start() {
        running = true;
        paused = false;
        if(runThread == null || !runThread.isAlive())
            runThread = new Thread(this);
        else if(runThread.isAlive())
            throw new IllegalStateException("Thread already started.");
        runThread.start();
    }

    public void stop() {
        if(runThread == null)
            throw new IllegalStateException("Thread not started.");
        synchronized (runThread) {
            try {
                running = false;
                runThread.notify();
                runThread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void pause() {
        if(runThread == null)
            throw new IllegalStateException("Thread not started.");
        synchronized (runThread) {
            paused = true;
        }
    }

    public void resume() {
        if(runThread == null)
            throw new IllegalStateException("Thread not started.");
        synchronized (runThread) {
            paused = false;
            runThread.notify();
        }
    }

    public void run() {
        long sleep = 0, before;
        while(running) {
            // get the time before we do our game logic
            before = System.currentTimeMillis();
            // move player and do all game logic
            try {
                // sleep for 100 - how long it took us to do our game logic
                sleep = 100-(System.currentTimeMillis()-before);
                Thread.sleep(sleep > 0 ? sleep : 0);
            } catch (InterruptedException ex) {
            }
            synchronized (runThread) {
                if(paused) {
                    try {
                        runThread.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        paused = false;
    }
}

请注意，您需要调用 gameThead.start() 来开始您的游戏！

Answer 2

在不消耗 100% CPU 的情况下创建一个好的（窗口应用程序）游戏循环实际上是一项非常棘手的任务。 Sidescroll 以恒定速度为 sprite 设置动画很容易引入急动，如果可以看到的话。

在运行了几个想法之后，这是最好的，横向滚动大部分时间都是黄油光滑的。 VSYNCing 是一种在窗口模式下是否有效的东西，我在不同的机器和操作系统上发现了不同的结果。

测试应用没有使用 SwingUI，因为大多数游戏都不需要它。 Gameloop 是一个活跃的更新-渲染循环，没有外部线程，使事情更容易编程。使用 keyPressed 回调更新 firePressed=true 等 标志变量并在循环中使用值。

运行测试应用 c:> java -cp ./classes GameLoop2 "fullscreen=false" "fps=60" "vsync=true"

//http://www.javagaming.org/index.php/topic,19971.0.html
//http://fivedots.coe.psu.ac.th/~ad/jg/ch1/ch1.pdf

import java.util.*;

import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferStrategy;

import java.awt.DisplayMode; // for full-screen mode

public class GameLoop2 implements KeyListener {
    Frame mainFrame;

    private static final long NANO_IN_MILLI = 1000000L; 

    // num of iterations with a sleep delay of 0ms before
    // game loop yields to other threads.
    private static final int NO_DELAYS_PER_YIELD = 16;

    // max num of renderings that can be skipped in one game loop,
    // game's internal state is updated but not rendered on screen.
    private static int MAX_RENDER_SKIPS = 5;

    private static int TARGET_FPS = 60;

    //private long prevStatsTime;
    private long gameStartTime;
    private long curRenderTime;
    private long rendersSkipped = 0L;
    private long period; // period between rendering in nanosecs

    long fps;
    long frameCounter;
    long lastFpsTime;

    Rectangle2D rect, rect2, rect3;

    /**
     * Create a new GameLoop that will use the specified GraphicsDevice.
     * 
     * @param device
     */
    public GameLoop2(Map<String,String> args, GraphicsDevice device) {
        try {
            if (args.containsKey("fps"))
              TARGET_FPS = Integer.parseInt(args.get("fps"));


            // Setup the frame
            GraphicsConfiguration gc = device.getDefaultConfiguration();

            mainFrame = new Frame(gc);
            //mainFrame.setUndecorated(true);
            mainFrame.setIgnoreRepaint(true);
            mainFrame.setVisible(true);
            mainFrame.setSize(640, 480);
            //mainFrame.setLocationRelativeTo();
            mainFrame.setLocation(700,100);
            mainFrame.createBufferStrategy(2);
            mainFrame.addKeyListener(this);

            if ("true".equalsIgnoreCase(args.get("fullscreen"))) {
              device.setFullScreenWindow(mainFrame);
              device.setDisplayMode(new DisplayMode(640, 480, 8, DisplayMode.REFRESH_RATE_UNKNOWN));
            }

            final boolean VSYNC = "true".equalsIgnoreCase(args.get("vsync"));

            // Cache the buffer strategy and create a rectangle to move
            BufferStrategy bufferStrategy = mainFrame.getBufferStrategy();

            rect = new Rectangle2D.Float(0,100, 64,64);
            rect2 = new Rectangle2D.Float(0,200, 32,32);
            rect3 = new Rectangle2D.Float(500,300, 128,128);

            // loop initialization
            long beforeTime, afterTime, timeDiff, sleepTime;
            long overSleepTime = 0L;
            int noDelays = 0;
            long excess = 0L;
            gameStartTime = System.nanoTime();
            //prevStatsTime = gameStartTime;
            beforeTime = gameStartTime;

            period = (1000L*NANO_IN_MILLI)/TARGET_FPS;  // rendering FPS (nanosecs/targetFPS)
            System.out.println("FPS: " + TARGET_FPS + ", vsync=" + VSYNC);
            System.out.println("FPS period: " + period);


            // Main loop
            while(true) {
               // **2) execute physics
               updateWorld(0);                  

               // **1) execute drawing
               Graphics g = bufferStrategy.getDrawGraphics();
               drawScreen(g);
               g.dispose();

               // Synchronise with the display hardware. Note that on
               // Windows Vista this method may cause your screen to flash.
               // If that bothers you, just comment it out.
               if (VSYNC) Toolkit.getDefaultToolkit().sync();

               // Flip the buffer
               if( !bufferStrategy.contentsLost() )
                   bufferStrategy.show();

               afterTime = System.nanoTime();
               curRenderTime = afterTime;
               calculateFramesPerSecond();

               timeDiff = afterTime - beforeTime;
               sleepTime = (period-timeDiff) - overSleepTime;
               if (sleepTime > 0) { // time left in cycle
                  //System.out.println("sleepTime: " + (sleepTime/NANO_IN_MILLI));
                  try {
                     Thread.sleep(sleepTime/NANO_IN_MILLI);//nano->ms
                  } catch(InterruptedException ex){}
                  overSleepTime = (System.nanoTime()-afterTime) - sleepTime;
               } else { // sleepTime <= 0;
                  System.out.println("Rendering too slow");
                  // this cycle took longer than period
                  excess -= sleepTime;
                  // store excess time value
                  overSleepTime = 0L;
                  if (++noDelays >= NO_DELAYS_PER_YIELD) {
                     Thread.yield();
                     // give another thread a chance to run
                     noDelays = 0;
                  }
               }

               beforeTime = System.nanoTime();

               /* If the rendering is taking too long, then
                  update the game state without rendering
                  it, to get the UPS nearer to the
                  required frame rate. */
               int skips = 0;
               while((excess > period) && (skips < MAX_RENDER_SKIPS)) {
                  // update state but don’t render
                  System.out.println("Skip renderFPS, run updateFPS");
                  excess -= period;
                  updateWorld(0);
                  skips++;
               }
               rendersSkipped += skips;
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            device.setFullScreenWindow(null);
        }
    }

    private void updateWorld(long elapsedTime) {
        // speed: 150 pixels per second
        //double xMov = (140f/(NANO_IN_MILLI*1000)) * elapsedTime;
        double posX = rect.getX() + (140f / TARGET_FPS);
    if (posX > mainFrame.getWidth())
        posX = -rect.getWidth();    
    rect.setRect(posX, rect.getY(), rect.getWidth(), rect.getHeight());

        posX = rect2.getX() + (190f / TARGET_FPS);
    if (posX > mainFrame.getWidth())
        posX = -rect2.getWidth();   
    rect2.setRect(posX, rect2.getY(), rect2.getWidth(), rect2.getHeight());         

        posX = rect3.getX() - (300f / TARGET_FPS);
    if (posX < -rect3.getWidth())
        posX = mainFrame.getWidth();
    rect3.setRect(posX, rect3.getY(), rect3.getWidth(), rect3.getHeight());         

    }

    private void drawScreen(Graphics g) {
        g.setColor(Color.BLACK);
        g.fillRect(0, 0, mainFrame.getWidth(), mainFrame.getHeight());
        g.setColor(Color.WHITE);
        g.drawString("FPS: " + fps, 40, 50);

        g.setColor(Color.RED);
        g.fillRect((int)rect.getX(), (int)rect.getY(), (int)rect.getWidth(), (int)rect.getHeight());

        g.setColor(Color.GREEN);
        g.fillRect((int)rect2.getX(), (int)rect2.getY(), (int)rect2.getWidth(), (int)rect2.getHeight());

        g.setColor(Color.BLUE);
        g.fillRect((int)rect3.getX(), (int)rect3.getY(), (int)rect3.getWidth(), (int)rect3.getHeight());
    }

    private void calculateFramesPerSecond() {
        if( curRenderTime - lastFpsTime >= NANO_IN_MILLI*1000 ) {
            fps = frameCounter;
            frameCounter = 0;
            lastFpsTime = curRenderTime;
        }
        frameCounter++;
    }

    public void keyPressed(KeyEvent e) {
        if( e.getKeyCode() == KeyEvent.VK_ESCAPE ) {
            System.exit(0);
        }
    }

    public void keyReleased(KeyEvent e) { }
    public void keyTyped(KeyEvent e) { }

    public static void main(String[] args) {
        try {
        Map<String,String> mapArgs = parseArguments(args);

            GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
            GraphicsDevice device = env.getDefaultScreenDevice();
            new GameLoop2(mapArgs, device);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }


    /**
     * Parse commandline arguments, each parameter is a name-value pair.
     * Example: java.exe MyApp "key1=value1" "key2=value2"
     */
    private static Map<String,String> parseArguments(String[] args) {
        Map<String,String> mapArgs = new HashMap<String,String>();

        for(int idx=0; idx < args.length; idx++) {
            String val = args[idx];
            int delimIdx = val.indexOf('=');
            if (delimIdx < 0) {
                mapArgs.put(val, null);
            } else if (delimIdx == 0) {
                mapArgs.put("", val.substring(1));
            } else {
                mapArgs.put(
                    val.substring(0, delimIdx).trim(),
                    val.substring(delimIdx+1)
                );
            }
        }

        return mapArgs;
    }

}

Gameloop 逻辑可能看起来很疯狂，但相信我，它运行得非常好。试一试。 编辑： 同时运行 TaskManager 会在流畅的动画中产生抖动我猜更新检测统计数据会带来沉重的打击。