线程与键绑定
我是新来的Java图形和线程，我试图做一个游戏（具体来说，庞）。 这个想法是，两个人可以在同一个键盘上玩（即有两个通过不同的键控制的桨）。 目前，双方球员不能同时移动他们的桨。
有没有解决这个问题？ 是单独的线程的答案？
如果可能，我希望桨能够同时移动（至少看起来）。
更新：好像使用Set<Integer>来存储按下的键是最好的选择。 我已经这样做了（而且它的工作原理），但我想知道是否有任何代码不在事件调度线程（EDT），如果我需要使用SwingUtilities.invokeLater(); 。 这是必要的代码：
private Set<Integer> keysDown = Collections.synchronizedSet(new HashSet<Integer>()); public void keyPressed(KeyEvent e) { keysDown.add(e.getKeyCode()); } public void keyReleased(KeyEvent e) { keysDown.remove(e.getKeyCode()); } public void updatePaddlePositions() { if (keysDown.contains(KeyEvent.VK_W)) paddleOne.move(-PADDLE_MOVE_INCREMENT); if (keysDown.contains(KeyEvent.VK_S)) paddleOne.move(PADDLE_MOVE_INCREMENT); if (keysDown.contains(KeyEvent.VK_UP)) paddleTwo.move(-PADDLE_MOVE_INCREMENT); if (keysDown.contains(KeyEvent.VK_DOWN)) paddleTwo.move(PADDLE_MOVE_INCREMENT); try { Thread.sleep(DELAY); } catch (InterruptedException e) { System.out.println("You Interrupted the game!"); } canvas.repaint(); }
这是canvas对象的paintComponent方法：
public void paintComponent(Graphics g) { super.paintComponent(g); paddleOne.paint(g); paddleTwo.paint(g); updatePaddlePositions(); // Does this need to be SwingUtilities.invokeLater(this)? // And should updatePaddlePositions() be run() as a result? }
这里是paddleOne和paddleTwo对象的paint方法：
public void paint(Graphics g) { g.setColor(Color.BLACK); g.fillRect(x, y, PADDLE_WIDTH, PADDLE_HEIGHT); }
随意评论我的设计，如果任何东西弹出“坏”给你。 最后， Collections.synchronizedSet(new HashSet<Integer>())意味着什么？
更新＃2：似乎键绑定是要走的路（即使他们需要更多的代码，在这种情况下）。 什么使键绑定更好？ 它是否与其他一切分开工作（并且不需要像关键听众那样的窗口焦点）？
另外，我明白HashSet<Integer>只是Set<Integer>的子类，但Collections.synchronizedSet(...)的目的是什么？ 我假设它与线程有关，但我不知道为什么它需要在这个程序（如果是的话）。
首先，使用Swing KeyBinding s除此之外，我还没有看到多线程的真正需求，除非你希望你的游戏是多线程的。
澄清问题是你需要能够让2名玩家按不同的键？
如果是这样：
解：
只需使用boolean s来标记一个键是否被按下，当键被释放时，你当然必须重置该标志。
在你的游戏逻辑中，你将检查状态，如果布尔和适当的行为。
看我下面的例子（两个桨可以独立移动使用W和S和UP和DOWN键）：
public class GameLogic { public GameLogic() { initComponents(); } private void initComponents() { JFrame frame = new JFrame("Game Test"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //create the gamepanel final GamePanel gp = new GamePanel(600, 500); //create panel to hold buttons to start pause and stop the game JPanel buttonPanel = new JPanel(); buttonPanel.setOpaque(false); final JButton startButton = new JButton("Start"); final JButton pauseButton = new JButton("Pause"); final JButton stopButton = new JButton("Stop"); pauseButton.setEnabled(false); stopButton.setEnabled(false); //add listeners to buttons (most of the actions - excuse the pun - takes palce here :) startButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent ae) { //clear enitites currently in array gp.clearEntities(); ArrayList<BufferedImage> ballEntityImages = new ArrayList<>(); ArrayList<Long> ballEntityTimings = new ArrayList<>(); ballEntityImages.add(createColouredImage("white", 50, 50, true)); ballEntityTimings.add(500l); Entity ballEntity = new Entity(gp.getWidth() / 2, gp.getHeight() / 2, ballEntityImages, ballEntityTimings); ballEntity.RIGHT = true; //create images for entities ArrayList<BufferedImage> advEntityImages = new ArrayList<>(); ArrayList<Long> advEntityTimings = new ArrayList<>(); advEntityImages.add(createColouredImage("orange", 10, 100, false)); advEntityTimings.add(500l); advEntityImages.add(createColouredImage("blue", 10, 100, false)); advEntityTimings.add(500l); //create entities AdvancedSpritesEntity player1Entity = new AdvancedSpritesEntity(0, 100, advEntityImages, advEntityTimings); ArrayList<BufferedImage> entityImages = new ArrayList<>(); ArrayList<Long> entityTimings = new ArrayList<>(); entityImages.add(createColouredImage("red", 10, 100, false)); entityTimings.add(500l);//as its the only image it doesnt really matter what time we put we could use 0l //entityImages.add(createColouredImage("magenta", 100, 100)); //entityTimings.add(500l); Entity player2Entity = new Entity(gp.getWidth() - 10, 200, entityImages, entityTimings); gp.addEntity(player1Entity); gp.addEntity(player2Entity);//just a standing still Entity for testing gp.addEntity(ballEntity);//just a standing still Entity for testing //create Keybingings for gamepanel GameKeyBindings gameKeyBindings = new GameKeyBindings(gp, player1Entity, player2Entity); GamePanel.running.set(true); //start the game loop which will repaint the screen runGameLoop(gp); startButton.setEnabled(false); pauseButton.setEnabled(true); stopButton.setEnabled(true); } }); pauseButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent ae) { boolean b = GamePanel.paused.get(); GamePanel.paused.set(!b);//set it to the opposite of what it was ie paused to unpaused and vice versa if (pauseButton.getText().equals("Pause")) { pauseButton.setText("Un-pause"); } else { pauseButton.setText("Pause"); } } }); stopButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent ae) { GamePanel.running.set(false); GamePanel.paused.set(false); /* if we want enitites to be cleared and a blank panel shown gp.clearEntities(); gp.repaint(); */ if (!pauseButton.getText().equals("Pause")) { pauseButton.setText("Pause"); } startButton.setEnabled(true); pauseButton.setEnabled(false); stopButton.setEnabled(false); } }); //add buttons to panel buttonPanel.add(startButton); buttonPanel.add(pauseButton); buttonPanel.add(stopButton); //add gamepanel to jframe and button panel frame.add(gp); frame.add(buttonPanel, BorderLayout.SOUTH); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } //Simply used for testing (to simulate sprites) can create different colored images public static BufferedImage createColouredImage(String color, int w, int h, boolean circular) { BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); Graphics2D g2 = img.createGraphics(); switch (color.toLowerCase()) { case "green": g2.setColor(Color.GREEN); break; case "magenta": g2.setColor(Color.MAGENTA); break; case "red": g2.setColor(Color.RED); break; case "yellow": g2.setColor(Color.YELLOW); break; case "blue": g2.setColor(Color.BLUE); break; case "orange": g2.setColor(Color.ORANGE); break; case "cyan": g2.setColor(Color.CYAN); break; case "gray": g2.setColor(Color.GRAY); break; default: g2.setColor(Color.WHITE); break; } if (!circular) { g2.fillRect(0, 0, img.getWidth(), img.getHeight()); } else { g2.fillOval(0, 0, img.getWidth(), img.getHeight()); } g2.dispose(); return img; } //Starts a new thread and runs the game loop in it. private void runGameLoop(final GamePanel gp) { Thread loop = new Thread(new Runnable() { @Override public void run() { gp.gameLoop(); } }); loop.start(); } //Code starts here public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { try {//attempt to set look and feel to nimbus Java 7 and up for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) { if ("Nimbus".equals(info.getName())) { UIManager.setLookAndFeel(info.getClassName()); break; } } } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { } GameLogic gameLogic = new GameLogic(); } }); } } class GameKeyBindings { public GameKeyBindings(JComponent gp, final Entity entity, final Entity entity2) { gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0, false), "W pressed"); gp.getActionMap().put("W pressed", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity.UP = true; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0, true), "W released"); gp.getActionMap().put("W released", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity.UP = false; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_S, 0, false), "S pressed"); gp.getActionMap().put("S pressed", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity.DOWN = true; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_S, 0, true), "S released"); gp.getActionMap().put("S released", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity.DOWN = false; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false), "down pressed"); gp.getActionMap().put("down pressed", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity2.DOWN = true; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "down released"); gp.getActionMap().put("down released", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity2.DOWN = false; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false), "up pressed"); gp.getActionMap().put("up pressed", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity2.UP = true; } }); gp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true), "up released"); gp.getActionMap().put("up released", new AbstractAction() { @Override public void actionPerformed(ActionEvent ae) { entity2.UP = false; } }); } } class AdvancedSpritesEntity extends Entity { public AdvancedSpritesEntity(int x, int y, ArrayList<BufferedImage> images, ArrayList<Long> timings) { super(x, y, images, timings); } void setAnimation(ArrayList<BufferedImage> images, ArrayList<Long> timings) { reset();//reset variables of animator class setFrames(images, timings);//set new frames for animation } } class Entity extends Animator { private int speed = 5; public boolean UP = false, DOWN = false, LEFT = false, RIGHT = false, visible; private Rectangle2D.Double rect; public Entity(int x, int y, ArrayList<BufferedImage> images, ArrayList<Long> timings) { super(images, timings); UP = false; DOWN = false; LEFT = false; RIGHT = false; visible = true; rect = new Rectangle2D.Double(x, y, getCurrentImage().getWidth(), getCurrentImage().getHeight()); } public void setSpeed(int speed) { this.speed = speed; } public int getSpeed() { return speed; } public boolean isVisible() { return visible; } public void setVisible(boolean visible) { this.visible = visible; } public HashSet<String> getMask(Entity e) { HashSet<String> mask = new HashSet<>(); int pixel, a; BufferedImage bi = e.getCurrentImage();//gets the current image being shown for (int i = 0; i < bi.getWidth(); i++) { // for every (x,y) component in the given box, for (int j = 0; j < bi.getHeight(); j++) { pixel = bi.getRGB(i, j); // get the RGB value of the pixel a = (pixel >> 24) & 0xff; if (a != 0) { // if the alpha is not 0, it must be something other than transparent mask.add((e.getX() + i) + "," + (e.getY() - j)); // add the absolute x and absolute y coordinates to our set } } } return mask; //return our set } // Returns true if there is a collision between object a and object b public boolean checkPerPixelCollision(Entity b) { // This method detects to see if the images overlap at all. If they do, collision is possible int ax1 = (int) getX(); int ay1 = (int) getY(); int ax2 = ax1 + (int) getWidth(); int ay2 = ay1 + (int) getHeight(); int bx1 = (int) b.getX(); int by1 = (int) b.getY(); int bx2 = bx1 + (int) b.getWidth(); int by2 = by1 + (int) b.getHeight(); if (by2 < ay1 || ay2 < by1 || bx2 < ax1 || ax2 < bx1) { return false; // Collision is impossible. } else { // Collision is possible. // get the masks for both images HashSet<String> maskPlayer1 = getMask(this); HashSet<String> maskPlayer2 = getMask(b); maskPlayer1.retainAll(maskPlayer2); // Check to see if any pixels in maskPlayer2 are the same as those in maskPlayer1 if (maskPlayer1.size() > 0) { // if so, than there exists at least one pixel that is the same in both images, thus return true; } } return false; } public void move() { if (UP) { rect.y -= speed; } if (DOWN) { rect.y += speed; } if (LEFT) { rect.x -= speed; } if (RIGHT) { rect.x += speed; } } @Override public void update(long elapsedTime) { super.update(elapsedTime); getWidth();//set the rectangles height accordingly after image update getHeight();//set rectangles height accordingle after update } public boolean intersects(Entity e) { return rect.intersects(e.rect); } public double getX() { return rect.x; } public double getY() { return rect.y; } public double getWidth() { if (getCurrentImage() == null) {//there might be no image (which is unwanted ofcourse but we must not get NPE so we check for null and return 0 return rect.width = 0; } return rect.width = getCurrentImage().getWidth(); } public double getHeight() { if (getCurrentImage() == null) { return rect.height = 0; } return rect.height = getCurrentImage().getHeight(); } } class Animator { private ArrayList<BufferedImage> frames; private ArrayList<Long> timings; private int currIndex; private long animationTime; private long totalAnimationDuration; private AtomicBoolean done;//used to keep track if a single set of frames/ an animtion has finished its loop public Animator(ArrayList<BufferedImage> frames, ArrayList< Long> timings) { currIndex = 0; animationTime = 0; totalAnimationDuration = 0; done = new AtomicBoolean(false); this.frames = new ArrayList<>(); this.timings = new ArrayList<>(); setFrames(frames, timings); } public boolean isDone() { return done.get(); } public void reset() { totalAnimationDuration = 0; done.getAndSet(false); } public void update(long elapsedTime) { if (frames.size() > 1) { animationTime += elapsedTime; if (animationTime >= totalAnimationDuration) { animationTime = animationTime % totalAnimationDuration; currIndex = 0; done.getAndSet(true); } while (animationTime > timings.get(currIndex)) { currIndex++; } } } public BufferedImage getCurrentImage() { if (frames.isEmpty()) { return null; } else { try { return frames.get(currIndex); } catch (Exception ex) {//images might have been altered so we reset the index and return first image of the new frames/animation currIndex = 0; return frames.get(currIndex); } } } public void setFrames(ArrayList<BufferedImage> frames, ArrayList< Long> timings) { if (frames == null || timings == null) {//so that constructor super(null,null) cause this to throw NullPointerException return; } this.frames = frames; this.timings.clear(); for (long animTime : timings) { totalAnimationDuration += animTime; this.timings.add(totalAnimationDuration); } } } class GamePanel extends JPanel { private final static RenderingHints textRenderHints = new RenderingHints(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON); private final static RenderingHints imageRenderHints = new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); private final static RenderingHints colorRenderHints = new RenderingHints(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY); private final static RenderingHints interpolationRenderHints = new RenderingHints(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC); private final static RenderingHints renderHints = new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY); public static AtomicBoolean running = new AtomicBoolean(false), paused = new AtomicBoolean(false); private int width, height, frameCount = 0, fps = 0; private ArrayList<Entity> entities = new ArrayList<>(); private final Random random = new Random(); public GamePanel(int w, int h) { super(true);//make sure double buffering is enabled setIgnoreRepaint(true);//mustnt repaint itself the gameloop will do that width = w; height = h; } @Override public Dimension getPreferredSize() { return new Dimension(width, height); } public void addEntity(Entity e) { entities.add(e); } void clearEntities() { entities.clear(); } //Only run this in another Thread! public void gameLoop() { //This value would probably be stored elsewhere. final double GAME_HERTZ = 30.0; //Calculate how many ns each frame should take for our target game hertz. final double TIME_BETWEEN_UPDATES = 1000000000 / GAME_HERTZ; //At the very most we will update the game this many times before a new render. //If you're worried about visual hitches more than perfect timing, set this to 1. final int MAX_UPDATES_BEFORE_RENDER = 5; //We will need the last update time. double lastUpdateTime = System.nanoTime(); //Store the last time we rendered. double lastRenderTime = System.nanoTime(); //If we are able to get as high as this FPS, don't render again. final double TARGET_FPS = 60; final double TARGET_TIME_BETWEEN_RENDERS = 1000000000 / TARGET_FPS; //Simple way of finding FPS. int lastSecondTime = (int) (lastUpdateTime / 1000000000); //store the time we started this will be used for updating map and charcter animations long currTime = System.currentTimeMillis(); while (running.get()) { if (!paused.get()) { double now = System.nanoTime(); long elapsedTime = System.currentTimeMillis() - currTime; currTime += elapsedTime; int updateCount = 0; //Do as many game updates as we need to, potentially playing catchup. while (now - lastUpdateTime > TIME_BETWEEN_UPDATES && updateCount < MAX_UPDATES_BEFORE_RENDER) { updateGame(elapsedTime);//Update the entity movements and collision checks etc (all has to do with updating the games status ie call move() on Enitites) lastUpdateTime += TIME_BETWEEN_UPDATES; updateCount++; } //If for some reason an update takes forever, we don't want to do an insane number of catchups. //If you were doing some sort of game that needed to keep EXACT time, you would get rid of this. if (now - lastUpdateTime > TIME_BETWEEN_UPDATES) { lastUpdateTime = now - TIME_BETWEEN_UPDATES; } drawGame();//draw the game by invokeing repaint (which will call paintComponent) on this JPanel lastRenderTime = now; //Update the frames we got. int thisSecond = (int) (lastUpdateTime / 1000000000); if (thisSecond > lastSecondTime) { //System.out.println("NEW SECOND " + thisSecond + " " + frameCount); fps = frameCount; frameCount = 0; lastSecondTime = thisSecond; } //Yield until it has been at least the target time between renders. This saves the CPU from hogging. while (now - lastRenderTime < TARGET_TIME_BETWEEN_RENDERS && now - lastUpdateTime < TIME_BETWEEN_UPDATES) { //allow the threading system to play threads that are waiting to run. Thread.yield(); //This stops the app from consuming all your CPU. It makes this slightly less accurate, but is worth it. //You can remove this line and it will still work (better), your CPU just climbs on certain OSes. //FYI on some OS's this can cause pretty bad stuttering. Scroll down and have a look at different peoples' solutions to this. //On my OS(Windows 7 x64 intel i3) it does not allow for time to make enityt etc move thus all stands still try { Thread.sleep(1); } catch (Exception e) { } now = System.nanoTime(); } } } fps = 0;//no more running set fps to 0 } private void drawGame() { //Both revalidate and repaint are thread-safe — you need not invoke them from the event-dispatching thread. http://docs.oracle.com/javase/tutorial/uiswing/layout/howLayoutWorks.html repaint(); } private void updateGame(long elapsedTime) { updateEntityMovements(elapsedTime); checkForCollisions(); } private void checkForCollisions() { if (entities.get(0).intersects(entities.get(2)) || entities.get(1).intersects(entities.get(2))) { if (entities.get(2).LEFT) { entities.get(2).RIGHT = true; entities.get(2).LEFT = false; } else { entities.get(2).LEFT = true; entities.get(2).RIGHT = false; } System.out.println("Intersecting"); } /* //This is best used when images have transparent and non-transparent pixels (only detects pixel collisions of non-transparent pixels) if (entities.get(0).checkPerPixelCollision(entities.get(2)) | entities.get(1).checkPerPixelCollision(entities.get(2))) { if (entities.get(2).LEFT) { entities.get(2).RIGHT = true; entities.get(2).LEFT = false; } else { entities.get(2).LEFT = true; entities.get(2).RIGHT = false; } System.out.println("Intersecting"); } */ } private void updateEntityMovements(long elapsedTime) { for (Entity e : entities) { e.update(elapsedTime); e.move(); } } @Override protected void paintComponent(Graphics grphcs) { super.paintComponent(grphcs); Graphics2D g2d = (Graphics2D) grphcs; applyRenderHints(g2d); drawBackground(g2d); drawEntitiesToScreen(g2d); drawFpsCounter(g2d); frameCount++; } public static void applyRenderHints(Graphics2D g2d) { g2d.setRenderingHints(textRenderHints); g2d.setRenderingHints(imageRenderHints); g2d.setRenderingHints(colorRenderHints); g2d.setRenderingHints(interpolationRenderHints); g2d.setRenderingHints(renderHints); } private void drawEntitiesToScreen(Graphics2D g2d) { for (Entity e : entities) { if (e.isVisible()) { g2d.drawImage(e.getCurrentImage(), (int) e.getX(), (int) e.getY(), null); } } } private void drawFpsCounter(Graphics2D g2d) { g2d.setColor(Color.WHITE); g2d.drawString("FPS: " + fps, 5, 10); } private void drawBackground(Graphics2D g2d) { g2d.setColor(Color.BLACK); g2d.fillRect(0, 0, getWidth(), getHeight()); //thanks to trashgod for lovely testing background :) http://stackoverflow.com/questions/3256269/jtextfields-on-top-of-active-drawing-on-jpanel-threading-problems/3256941#3256941 g2d.setColor(Color.BLACK); for (int i = 0; i < 128; i++) { g2d.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));//random color g2d.drawLine(getWidth() / 2, getHeight() / 2, random.nextInt(getWidth()), random.nextInt(getHeight())); } } }
这对于提供给KeyListener的低级访问可能是合法的用例。 请参阅如何编写密钥监听器和KeyEventDemo ; 不要忘记requestFocusInWindow() 。 另外考虑提供一个播放器的键盘控制和另一个播放器的鼠标控制。
附录：@David Kroukamp使用键绑定提出了一个吸引人的反例 。 作为参考， 这里引用的例子说明了一种管理密钥偏好的方法。
