Java密钥事件不起作用

Question

我正在尝试理解Java事件但我遇到了关键事件的问题。在我的代码中，关键事件不起作用。当我创建这一行add(button);时，会出现问题（我想是这样）。我该怎么办？

代码：

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;



public class KeyTest extends JFrame implements KeyListener {

    static JButton button;
    private int counter = 0;
    private String userInput = "";
    private final String secret = "secret";

    public KeyTest() {
        super("KeyListener Test");
        addKeyListener(this);
        ActionListener lol = new Akcja();
        button = new JButton("tura");
        button.addActionListener(lol);
        add(button);
        pack();
        Dimension dimension = new Dimension(400, 400);
        setPreferredSize(dimension);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    @Override
    public void keyPressed(KeyEvent evt) {
    }

    @Override
    public void keyReleased(KeyEvent evt) {
        char c = evt.getKeyChar();
        if(counter < secret.length())
            checkSecret(c);
    }

    @Override
    public void keyTyped(KeyEvent evt) {

    }

    private void checkSecret(char c) {
        if(c == secret.charAt(counter)) {
            counter++;
            userInput = userInput+c;
        }
        else {
            counter = 0;
            userInput = userInput+c;

        }


            setTitle(userInput);
    }
    static class Akcja implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent e) {

            //to-do
        }

    }
}