Java ActionListener 显示错误输出

Question

我在 Java (Eclipse) 中的 ActionListener 有问题。该程序应该问你关于数学中不同主题的问题。这是代码的一部分，其中包含问题：

public Frame () {
    c = getContentPane();
    c.setLayout(new BorderLayout());

    menuBar = new JMenuBar();
    menu = new JMenu("Test");
    menu.setMnemonic(KeyEvent.VK_A);        
    addition = new JMenuItem("Addition");
    addition.setMnemonic(KeyEvent.VK_B);
    menu.add(addition);     
    minus = new JMenuItem("Subtraction");
    minus.setMnemonic(KeyEvent.VK_C);
    menu.add(minus);        
    setJMenuBar(menuBar);
    menuBar.add(menu);

    answer = new JButton("Answer");
    c.add(answer, BorderLayout.SOUTH);

    next = new JButton("Next");
    c.add(next, BorderLayout.EAST);

    back = new JButton("Back");
    c.add(back, BorderLayout.WEST);

    beschriftung = new JLabel();
    beschriftung.setText("Welcome! Please choose your desired operation at the top.");
    beschriftung.setVerticalTextPosition(JLabel.CENTER);
    beschriftung.setHorizontalAlignment(JLabel.CENTER);
    c.add(beschriftung,BorderLayout.CENTER);    

    next.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            i = 1+dice.nextInt(99);
            j = 1+dice.nextInt(99);
            k = i + j;
            beschriftung.setText("Next Question: " + i + "+" + j);
        }
    });


addition.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent a) {
        beschriftung.setText("Addition Questions!");    
        c.remove(nextminus);
        next = new JButton("Next");
        c.add(next, BorderLayout.EAST); 

        next.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent b) {
                i = 1+dice.nextInt(99);
                j = 1+dice.nextInt(99);
                k = i + j;
                beschriftung.setText("Next Question: " + i + "+" + j);

            }
        });

        answer2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent d) {
                beschriftung.setText(i + "+" + j + "= " + k);
            }
        });

    }
});

minus.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        beschriftung.setText("Subtraction Questions!"); 
        c.remove(next);
        nextminus = new JButton("Next!");
        c.add(nextminus, BorderLayout.EAST);

        nextminus.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent f) {
                i = 1+dice.nextInt(99);
                j = 1+dice.nextInt(99);
                k = i - j;
                beschriftung.setText("Next Question: " + i + "-" + j);
            }
        });

        answer.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent g) {
                beschriftung.setText(i + "-" + j + "= " + k);
             }
        });
    }
});

}

当我在添加选项卡中单击 JButton "answer" 时，它没有输出任何内容。

有人知道解决方案吗？

Answer 1

您似乎将动作侦听器设置到了错误的按钮。尝试在添加菜单栏项的动作侦听器中使用 answer.addActionListener() 而不是 answer2.addActionListener()。

Java ActionListener 显示错误输出

Java ActionListener displaying false output

java

actionlistener