在Java GUI中更换卡时，KeyListener不工作

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class CardSwitchingExample {
    private JFrame frame;
    private JPanel cardPanel;
    private CardLayout cardLayout;

    public CardSwitchingExample() {
        frame = new JFrame("Card Switching Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        cardPanel = new JPanel();
        cardLayout = new CardLayout();
        cardPanel.setLayout(cardLayout);

        JPanel card1 = new JPanel();
        card1.add(new JLabel("Card 1"));
        JButton switchToCard2 = new JButton("Switch to Card 2");
        card1.add(switchToCard2);

        JPanel card2 = new JPanel();
        card2.add(new JLabel("Card 2"));
        JButton switchToCard1 = new JButton("Switch to Card 1");
        card2.add(switchToCard1);

        cardPanel.add(card1, "Card 1");
        cardPanel.add(card2, "Card 2");

        switchToCard2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                cardLayout.show(cardPanel, "Card 2");
                card2.requestFocus(); // 确保焦点转移到新的卡上
            }
        });

        switchToCard1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                cardLayout.show(cardPanel, "Card 1");
                card1.requestFocus(); // 确保焦点转移到新的卡上
            }
        });

        frame.add(cardPanel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new CardSwitchingExample();
            }
        });
    }
}