Java 我的循环有什么问题？

所以我试图通过减少行数，使用大量循环来优化我的代码。但它一直……有问题

我只是想显示一串单选按钮，只显示两个按钮，两个按钮都不做任何事情

我只是想知道是否有人可以批评我的代码，告诉这个新手他哪里出了问题

感谢您的帮助：

import java.awt.event.*;
import javax.swing.*;  
import javax.swing.JOptionPane;
import javax.swing.JFrame;
import javax.swing.JLabel;
import java.awt.BorderLayout;
import java.awt.Color;


public class NewGame implements ActionListener {

    private final String[] premierLeagueClubs = {"Arsenal", "Bournemouth", "Burnley", "Chelsea", "Crystal Palace",
        "Everton", "Hull City", "Leicester City", "Liverpool", "Manchester United", "Manchester City", "Middlesborough",
        "Southampton", "Stoke City", "Sunderland", "Swansea City", "Tottenham Hotspur", "Watford", "West Brom", "West Ham"};
    private final JRadioButton[] rb = new JRadioButton[20];
    JFrame f3;
    private final JButton b, quit;
    String teamName;
    JLabel label1;
    private static JPanel chooseClubPanel;

    public NewGame() {
        f3 = new JFrame("Ballon d'or");
        f3.setExtendedState(JFrame.MAXIMIZED_BOTH);
        f3.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);

        chooseClubPanel = new JPanel();
        f3.add(chooseClubPanel, BorderLayout.CENTER);
        chooseClubPanel.setBackground(Color.GREEN);

        label1 = new JLabel("Please choose a team");
        chooseClubPanel.add(label1);

        ButtonGroup bg = new ButtonGroup();

        int startvalueBG;
        int endvalueBG = 19;
        for (startvalueBG = 0; startvalueBG <= endvalueBG; startvalueBG++) {
            bg.add(rb[startvalueBG]);
        }

        b = new JButton("OK");
        b.addActionListener(this);
        chooseClubPanel.add(b);

        quit = new JButton("Quit");
        quit.addActionListener(this);
        chooseClubPanel.add(quit);

        int startValueAddRB;
        int endValueAddRB = 19;
        for (startValueAddRB = 0; startValueAddRB <= endValueAddRB; startValueAddRB++) {
            f3.add(rb[startValueAddRB]);
        }

        int startRB;
        int endRB = 19;

        for (startRB = 0; endRB <= 19; startRB++) {
            for (int i = 0; i < premierLeagueClubs.length; i++) {
                rb[startRB] = new JRadioButton(premierLeagueClubs[i]);
                chooseClubPanel.add(rb[i]);
            }
        }
        f3.addWindowListener(new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent e) {
                if (JOptionPane.showConfirmDialog(f3, "Are you sure ?", "Warning", JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION) {
                    f3.setVisible(false);
                    f3.dispose();
                } else {

                    f3.setVisible(true);
                }
            }
        });
    }

    public void setFrame(JFrame f3) {
        this.f3 = f3;
    }

    public JFrame getFrame() {

        return f3;
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        int rbNumber;
        int rbNumberMax = 19;

        for (rbNumber = 0; rbNumber < rbNumberMax; rbNumber++) {
            if (rb[rbNumber].isSelected()) {
                teamName = rb[rbNumber].getText();
                f3.dispose();
                JOptionPane.showMessageDialog(f3, "You chose : " + rb[rbNumber].getText());

            }
        }

    }

}

---

>让我们看一下代码…< /P> 首先，您尝试将每个按钮添加到ButtonGroup，但实际上尚未创建任何可能的NullPointerException

然后，您尝试将按钮添加到chooseClubPanel，有效地从帧中删除，但索引都混乱不堪，您正在创建19x19个按钮，每个球杆都分配给所有19个，并且有效地替换为下一个球杆

int startRB;
int endRB = 19;

for (startRB = 0; endRB <= 19; startRB++) {
    for (int i = 0; i < premierLeagueClubs.length; i++) {
        rb[startRB] = new JRadioButton(premierLeagueClubs[i]);
        chooseClubPanel.add(rb[i]);
    }
}

在需要显示的某个时刻，最简单的解决方案是只添加您想要的任何容器，比如JFrame

---

通常我建议看一看，但在你的例子中，我认为看一看

会更实际，根据你提供的示例代码，你会遇到一个NullPointerException，因为rb实际上不包含任何Tanks，我已经修复了它，但我更感兴趣的是我循环的逻辑。单选按钮没有出现在我的gui中。如果我单独写每一行，我可以让它们出现，所以我认为这是我循环的逻辑。任何帮助都将不胜感激：您是否真的向容器中添加了任何按钮？是的，如果我逐行添加它们，单选按钮将显示在我的gui中。然而，与其写20行代码，不如尝试for循环。这段代码应该将单选按钮添加到我的JPanel中，是的，JPanel被添加到我的JFrame中；谢谢你，这让我想了很多。特别是，我将为我的其他类探讨只使用一个JFrame并像您一样扩展JPanel的概念。我的JFrame不会很快出现，我正在创建一个JFrame，执行一些操作，然后使用dispose方法删除JFrame并重复此过程数次。这是可行的，但即使是这个新手也能看出这远非理想。感谢您的反馈：

int startValueAddRB;
int endValueAddRB = 19;
for (startValueAddRB = 0; startValueAddRB <= endValueAddRB; startValueAddRB++) {
    f3.add(rb[startValueAddRB]);
}

int startRB;
int endRB = 19;

for (startRB = 0; endRB <= 19; startRB++) {
    for (int i = 0; i < premierLeagueClubs.length; i++) {
        rb[startRB] = new JRadioButton(premierLeagueClubs[i]);
        chooseClubPanel.add(rb[i]);
    }
}

public class NewGame extends JPanel implements ActionListener {

    private final String[] premierLeagueClubs = {"Arsenal", "Bournemouth", "Burnley", "Chelsea", "Crystal Palace",
                                                                                             "Everton", "Hull City", "Leicester City", "Liverpool", "Manchester United", "Manchester City", "Middlesborough",
                                                                                             "Southampton", "Stoke City", "Sunderland", "Swansea City", "Tottenham Hotspur", "Watford", "West Brom", "West Ham"};
    private final JRadioButton[] rb = new JRadioButton[20];
    private final JButton b, quit;
    String teamName;
    JLabel label1;

    ButtonGroup bg = new ButtonGroup();

    public NewGame() {
        setBackground(Color.GREEN);

        label1 = new JLabel("Please choose a team");
        add(label1);

        for (int i = 0; i < premierLeagueClubs.length; i++) {
            rb[i] = new JRadioButton(premierLeagueClubs[i]);
            rb[i].setActionCommand(premierLeagueClubs[i]);
            bg.add(rb[i]);
            add(rb[i]);
        }

        b = new JButton("OK");
        b.addActionListener(this);
        add(b);

        quit = new JButton("Quit");
        quit.addActionListener(this);
        add(quit);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("You have selected " + bg.getSelection().getActionCommand());
    }

}

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            JFrame frame = new JFrame("Title");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(new NewGame());
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }
    });
}