JButton上的ActionListener不执行任何操作

Question

我的Actionlistener有一个小问题,当我点击按钮没有任何反应？我没有看到问题所在,所以另一双眼睛可以帮助我:)

 public class GameOptions extends JPanel implements ActionListener{ 
    public GameOptions(){
        System.out.println("GameOptions Class test blabla");

        easyButton().addActionListener(this);
        mediumButton().addActionListener(this);
        hardButton().addActionListener(this);

        JPanel center = new JPanel(new GridLayout(4,1,10,10));
        center.add(new JLabel("Chose Difficulty Level"));
        center.add(easyButton());
        center.add(mediumButton());
        center.add(hardButton());

        this.add(center, BorderLayout.CENTER);
        this.setPreferredSize(this.getPreferredSize()); 
        this.setFocusable(true);
        this.requestFocusInWindow();
    }
    private JButton easyButton(){
        JButton levelEasy = new JButton("Easy");
        return levelEasy;
    }
    private JButton mediumButton(){
        JButton levelMedium = new JButton("Medium");
        return levelMedium;
    }
    private JButton hardButton(){
        JButton levelHard = new JButton("Hard");
        return levelHard;
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        Object src = e.getSource();
        if(src == easyButton()){
            System.out.println("Easy");
        }
        else if(src == mediumButton()){
            System.out.println("Medium");
        }
        else if(src == hardButton()){
            System.out.println("Hard");
        }
        else{

        }
      }
    }

Answer 1

您的xxxButton()方法每次都会创建新的JButton,因此您将ActionListener添加到新创建的JButton中,然后丢弃该按钮,然后添加一个完全不同的JButton,一个没有ActionListener的JButton到GUI.

建议:创建JButtons,为它们设置变量,添加ActionListener,并将相同的按钮添加到GUI.

所以不是这样的:

easyButton().addActionListener(this);  // creates one JButton

center.add(easyButton());   // creates a completey different JButton

做这个:

JButton easyButton = easyButton();
easyButton.addActionListener(this);

center.add(easyButton);

注意,如果这是我的代码,我不确定我是否会使用JButtons.相反,也许我会使用JRadioButtons或JComboBox.