布尔变量不会更改为 true

Question

我正在编写一个类来在屏幕上移动一个圆圈，但主要问题是布尔变量没有更改为true，尽管我试图使它们更改为true。我不知道我做错了什么。请帮忙。谢谢。

public class Restart extends Panel implements KeyListener {
    static final int left = 37;
    static final int right = 39;
    static final int down = 40;
    static final int up = 38;
    static boolean leftPress = false;
    static boolean rightPress = false;
    static boolean upPress = false;
    static boolean downPress = false;
    static int x1 = 0;
    static int y1 = 0;
    Restart(int width, int length, int minusBy) {
        super(width, length, minusBy);
    }
    public static void main(String args[]) throws InterruptedException {
        Restart panel = new Restart(500, 500, 9);
        JFrame frame = new JFrame("Fishy");
        frame.add(panel);
        Frame.showFrame(frame);
        while (true) {
            if (upPress) {
                y1--;
            }
            if (downPress) {
                y1++;
            }
            if (leftPress) {
                x1--;
            }
            if (rightPress) {
                x1++;
            }
            Thread.sleep(1);
            frame.repaint();
        }
    }
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.fillOval(x1, y1, 50, 50);
    }
    @Override
    public void keyPressed(KeyEvent e) {
        if (up == e.getKeyCode()) {
            upPress = true;
        }
        if (down == e.getKeyCode()) {
            downPress = true;
        }
        if (left == e.getKeyCode()) {
            leftPress = true;
        }
        if (right == e.getKeyCode()) {
            rightPress = true;
        }
    }
    @Override
    public void keyReleased(KeyEvent e) {
        if (up == e.getKeyCode()) {
            upPress = false;
        }
        if (down == e.getKeyCode()) {
            downPress = false;
        }
        if (left == e.getKeyCode()) {
            leftPress = false;
        }
        if (right == e.getKeyCode()) {
            rightPress = false;
        }
    }
    /* NOT USING */
    @Override
    public void keyTyped(KeyEvent e) {
    }
}

Answer 1

从不将密钥侦听器添加到任何组件。因此，您不会获得任何输入。通过调用 someComponent.addKeyListener(this) 将重新启动作为密钥侦听器添加到某些Component（JPanel和其他一些可能需要使用 setFocusable(true) 使某些可聚焦）。我建议您将侦听器添加到Restart实例本身。