单击 canvas 后 KeyListener 停止工作

KeyListener stops working after clicking canvas

我很简单KeyHandler

public class KeyHandler implements KeyListener {
    private final Set<Integer> keyEvents = new LinkedHashSet<>();
    public Set<Integer> pressedKeys() {
        return keyEvents;
    }

    @Override
    public void keyPressed(KeyEvent e) {
        keyEvents.add(e.getKeyCode());
    }

    @Override
    public void keyReleased(KeyEvent e) {
        keyEvents.remove(e.getKeyCode());
    }

    @Override
    public void keyTyped(KeyEvent e) {

    }
}

添加到 JFrame
frame.addKeyListener(keyListener);

休息可能无关紧要,但我将相同的实例传递给 KeyBinder

public class KeyBinder {
    private final Map<Integer, GameEvent> bindings = new HashMap<>();
    private final KeyHandler keyHandler;

    public KeyBinder(KeyHandler keyHandler) {
        this.keyHandler = keyHandler;
        bindings.put(KeyEvent.VK_A, MoveEvent.MOVE_LEFT);
        bindings.put(KeyEvent.VK_D, MoveEvent.MOVE_RIGHT);
        bindings.put(KeyEvent.VK_S, MoveEvent.MOVE_DOWN);
        bindings.put(KeyEvent.VK_W, MoveEvent.MOVE_UP);
    }

    public List<GameEvent> mapEvents() {
        final var events = new ArrayList<GameEvent>();
        keyHandler.pressedKeys().forEach(key -> events.add(bindings.get(key)));
        return events;
    }
}

然后,我将那些 GameEvents 传递给 Player 实例让他移动

@Override
public void update(java.util.List<GameEvent> events) {
    events.forEach(this::handleEvent);
}

private void handleEvent(GameEvent event) {
    if (event instanceof MoveEvent) {
        updatePosition((MoveEvent) event);
    }
}

private void updatePosition(MoveEvent event) {
    switch (event) {
        case MOVE_UP -> position = new Position(position.getX(), position.getY() - speed);
        case MOVE_DOWN -> position = new Position(position.getX(), position.getY() + speed);
        case MOVE_RIGHT -> position = new Position(position.getX() + speed, position.getY());
        case MOVE_LEFT -> position = new Position(position.getX() - speed, position.getY());
    }
}

如果我是 运行我的应用程序的单个实例,它工作得很好。但是,因为那是打算成为在线游戏,所以我想同时 运行 2 个实例进行测试。不幸的是,我启动了第二个实例,我的 KeyHandler 在其中任何一个都不再工作,它只是不记录任何 KeyEvents。我知道我的应用程序仍在 运行ning,因为我的服务器应用程序一直在从两个客户端接收数据。

编辑:

我刚刚意识到还有其他问题。单击 canvas 后 KeyHandler 停止工作...我什至不需要我的应用程序的第二个实例。这是我用来画东西的 JFrameCanvas 的代码...

 public class Display {
        private JFrame frame;
        private Canvas canvas;
    
        public Display(KeyListener keyListener) {
            initFrame(keyListener);
            initCanvas();
            frame.add(canvas);
            frame.pack();
        }
    
        private void initFrame(KeyListener keyListener) {
            frame = new JFrame(GameConfig.TITLE);
            frame.setSize(GameConfig.SCREEN_WIDTH, GameConfig.SCREEN_HEIGHT);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setResizable(false);
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
            frame.addKeyListener(keyListener);
        }
    
        private void initCanvas() {
            canvas = new Canvas();
            canvas.setPreferredSize(new Dimension(GameConfig.SCREEN_WIDTH, GameConfig.SCREEN_HEIGHT));
            canvas.setMaximumSize(new Dimension(GameConfig.SCREEN_WIDTH, GameConfig.SCREEN_HEIGHT));
            canvas.setMinimumSize(new Dimension(GameConfig.SCREEN_WIDTH, GameConfig.SCREEN_HEIGHT));
        }
    
        public Canvas getCanvas() {
            return canvas;
        }
    }

您的键监听器没有监听任何键事件的原因是键监听器仅在组件具有焦点时才工作。好像当您单击 canvas 时,canvas 现在是焦点的所有者,因此框架不再聚焦。

一般来说,我建议为此使用键绑定。即使您的组件未获得焦点,键绑定也可以侦听键事件。但是如果你想继续使用KeyListeners,这里有两个解决方案:

Add a FocusListener to the frame.

    frame.addFocusListener(new FocusListener() {
            public void focusGained(FocusEvent e) {}
            public void focusLost(FocusEvent e) {frame.requestFocus();}
    });

Disable the focusability of canvas.

    canvas.setFocusable(false);

不推荐使用这些解决方案,但它应该适合您的情况。