按住KeyEvent时，如何仅一次? [英] How do I the KeyEvent only once when it is held down?

问题描述

我正在尝试以一定的速度射击导弹，但是目前您可以简单地按住发射按钮(太空)，它将连续制造一列导弹.

I am trying to shoot a missile at a certain rate but currently you can simple hold down the fire button (Space) and it will make a continuous line of missiles.

我相信这是因为KeyEvent是在您按住KeyEvent时触发的，而我要做的只是在按住它时触发一次.

I believe this is because the KeyEvent is being triggered when you hold it down when what I need it to do is only trigger once when you hold it down.

我如何使它检测到仅按下一次按钮就被按下?

How would I make it detect the holding down of a button as only pressing it once?

public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();
    if (key == KeyEvent.VK_SPACE) {
        fire();
    }

    if (key == KeyEvent.VK_A) {
        dx = -1;
    }

    if (key == KeyEvent.VK_D) {
        dx = 1;
    }
}

public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();
    if (key == KeyEvent.VK_SPACE) {

    }
    if (key == KeyEvent.VK_A) {
        dx = 0;
    }

    if (key == KeyEvent.VK_D) {
        dx = 0;
    }
}

推荐答案

只需添加一个检查以确保您已释放密钥，然后再允许自己启动即可.我使用 AtomicBoolean 以确保不会因触发不同事件而产生多线程问题.

Just add a check to make sure you've released the key before allowing yourself to fire again. I use AtomicBoolean to ensure there are no multithreading issues by the different events getting fired.

private final AtomicBoolean canShoot = new AtomicBoolean(true);

public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();

    if (key == KeyEvent.VK_SPACE) {
        if (canShoot.compareAndSet(true, false)) {
            fire();
        }
    }
    // snip
}

public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();

    if (key == KeyEvent.VK_SPACE) {
        canShoot.set(true);
    }
    // snip
}

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