Swing 的 KeyListener 和同时按下的多个键 [英] Swing's KeyListener and multiple keys pressed at the same time

问题描述

当同时按下两个键盘键时，是否有任何传统的跟踪事件的摆动方式?我有几个想法，例如记住键和事件生成时间，以便我们可以在连续的事件处理程序调用中检查这两个事件之间的时间差并决定它是否是一个双按钮事件.但它看起来像一团糟.

is there any conventional way in swing of tracking down the events, when two keyboard keys are pressed at the same time? I have a couple of ideas e.g. remembering the key and event generation time so that we could in a consecutive event handler invocation check the time difference between these two events and decide, whether it's a two-button event or not. But it looks like a kludge.

推荐答案

使用集合来记住当前按下了哪些键，并检查每次按下一个键时是否按下了多个键.

Use a collection to remember which keys are currently pressed and check to see if more than one key is pressed every time a key is pressed.

class MultiKeyPressListener implements KeyListener {
    // Set of currently pressed keys
    private final Set<Integer> pressedKeys = new HashSet<>();

    @Override
    public synchronized void keyPressed(KeyEvent e) {
        pressed.add(e.getKeyCode());
        Point offset = new Point();
        if (!pressedKeys.isEmpty()) {
            for (Iterator<Integer> it = pressedKeys.iterator(); it.hasNext();) {
                switch (it.next()) {
                    case KeyEvent.VK_W:
                    case KeyEvent.VK_UP:
                        offset.y = -1;
                        break;
                    case KeyEvent.VK_A:
                    case KeyEvent.VK_LEFT:
                        offset.x = -1;
                        break;
                    case KeyEvent.VK_S:
                    case KeyEvent.VK_DOWN:
                        offset.y = 1;
                        break;
                    case KeyEvent.VK_D:
                    case KeyEvent.VK_RIGHT:
                        offset.x = 1;
                        break;
                }
            }
        }
        System.out.println(offset); // Do something with the offset.
    }

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

    @Override
    public void keyTyped(KeyEvent e) { /* Not used */ }
}

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