线程“主”java.lang.StackOverflowError JPanel 中的异常

Question

当我尝试运行在框架内创建面板的程序时遇到此错误

我没有粘贴变量声明之类的部分代码，因为我没有太多空间！

Exception in thread "main" java.lang.StackOverflowError
    at java.util.HashMap.hash(HashMap.java:338)
        at java.util.HashMap.get(HashMap.java:556)
        at javax.swing.UIDefaults$TextAndMnemonicHashMap.get(UIDefaults.java:1244)
        at javax.swing.UIDefaults.getFromResourceBundle(UIDefaults.java:288)
        at javax.swing.UIDefaults.get(UIDefaults.java:162)
        at javax.swing.MultiUIDefaults.get(MultiUIDefaults.java:64)
        at javax.swing.UIDefaults.getUI(UIDefaults.java:753)
        at javax.swing.UIManager.getUI(UIManager.java:1016)
        at javax.swing.JPanel.updateUI(JPanel.java:126)
        at javax.swing.JPanel.<init>(JPanel.java:86)

LoginWindow.java:

创建主面板，分为包含标签、文本字段和按钮的子面板

public class LoginWindow extends JPanel {

    public LoginWindow() {

        LoginWindow p1 = new LoginWindow();
        LoginWindow p2 = new LoginWindow();
        LoginWindow p3 = new LoginWindow();
        LoginWindow p4 = new LoginWindow();
        LoginWindow p5 = new LoginWindow();
        LoginWindow p0 = new LoginWindow();

        p1.setLayout(new BorderLayout());
        p2.setLayout(new BorderLayout());
        p3.setLayout(new GridLayout(3, 1, 1, 1));
        p4.setLayout(new GridLayout(3, 1, 1, 1));
        p5.setLayout(new GridBagLayout());
        p0.setLayout(new BorderLayout());

        password = new JPasswordField();
        email = new JTextField();
        label_password = new JLabel("Password");
        label_email = new JLabel("Email");

        setLayout(new BorderLayout());

        add(p0,BorderLayout.NORTH);
        add(p1,BorderLayout.CENTER);
        add(p2,BorderLayout.SOUTH);

        sign_in = new JLabel("Sign in");
        sign_in.setFont(new Font("Serif", Font.PLAIN, 25));
        sign_in.setForeground(Color.red);
        p0.add(sign_in,BorderLayout.CENTER);

        p1.add(p3, BorderLayout.SOUTH);
        p1.add(p4, BorderLayout.NORTH);     

        p1.setBorder(BorderFactory.createLineBorder(Color.gray, 1, true));

        p4.add(label_email);
        p4.add(email);

        p3.add(label_password);
        p3.add(password);

        button = new Button("Create Account");
        button.setPreferredSize(new Dimension(120, 30));
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                if(blank.equals(password.getPassword().toString()) || blank.equals(email.getText())){
                    JOptionPane.showMessageDialog(null, "Email or password missing !");
                }else {
                    DataBase db = new DataBase();
                    db.insertData(password.getPassword().toString(), email.getText());
                }
            }
        });

        p5.add(button);
        p2.add(p5,BorderLayout.CENTER);
    }
}

window.java:

从窗口类创建一个对象，并将创建的面板添加到选项卡式窗格中，全部在主框架内

public class window extends JFrame {

    public window() {
        super("Window");
        setSize(300,230);
        setVisible(true);
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        //setResizable(false);
        setLocation(600, 100);

        JTabbedPane tabPane = new JTabbedPane();
        LoginWindow panel = new LoginWindow();
        tabPane.addTab("Sign in",panel );

        add(tabPane);
        //pack();
    }

    public static void main(String[] args) {
        window frame = new window();
    }
}

Answer 1

public class LoginWindow extends JPanel {

     public LoginWindow() {

                LoginWindow p1 = new LoginWindow();

您正在尝试在 LoginWindow 的构造函数中实例化 LoginWindow。因此递归。

可能你需要另一个类/面板并在这里使用它？

Answer 2

您正在为 LoginWindow 的构造函数中创建 6 个新的 LoginWindow。 这会导致无限循环。

这个循环一直循环下去，直到出现堆栈溢出：

public LoginWindow() {

            LoginWindow p1 = new LoginWindow();
            LoginWindow p2 = new LoginWindow();
            LoginWindow p3 = new LoginWindow();
            LoginWindow p4 = new LoginWindow();
            LoginWindow p5 = new LoginWindow();
            LoginWindow p0 = new LoginWindow();

根据您的代码尝试以下操作：

您所要做的就是添加适当的布局以正确定位您的元素：

class LoginWindow extends JFrame{


    public LoginWindow() {
        JPasswordField password = new JPasswordField();
        JTextField email = new JTextField();
        JLabel label_password = new JLabel("Password");
        JLabel label_email = new JLabel("Email");

        JLabel sign_in = new JLabel("Sign in");
        sign_in.setFont(new Font("Serif", Font.PLAIN, 25));
        sign_in.setForeground(Color.red);

        Button button = new Button("Create Account");
        button.setPreferredSize(new Dimension(120, 30));
        button.addActionListener(new ActionListener() {

        String blank = "";

            @Override
            public void actionPerformed(ActionEvent e) {
                if(blank.equals(password.getPassword().toString()) || blank.equals(email.getText())){
                    JOptionPane.showMessageDialog(null, "Email or password missing !");
                }else {

                }
            }
        });


        setVisible(true);
        setSize(300,230);
        setLocation(600, 100);

        JPanel panel = new JPanel();

        panel.add(label_email);
        email.setPreferredSize(new Dimension(100,20));
        panel.add(email);

        panel.add(label_password);
        password.setPreferredSize(new Dimension(100,20));
        panel.add(password);


        panel.add(button);

        this.getContentPane().add(panel);
        setDefaultCloseOperation(EXIT_ON_CLOSE);


    }

}

然后运行：

public static void main(String[] args) {
    LoginWindow frame = new LoginWindow();    
   }

Answer 3

我添加了一个新的构造函数：

public LoginWindow(LayoutManager l) {
    //Constructor for the main panel
}

public LoginWindow() {

    setLayout(new BorderLayout());

    LoginWindow p1 = new LoginWindow(new BorderLayout());
    LoginWindow p2 = new LoginWindow(new BorderLayout());
    LoginWindow p3 = new LoginWindow(new GridLayout(2, 1, 1, 1));
    LoginWindow p4 = new LoginWindow(new GridLayout(2, 1, 1, 1));
    LoginWindow p5 = new LoginWindow(new GridBagLayout());
    LoginWindow p0 = new LoginWindow(new BorderLayout());

...
}

当你在 window.java 中创建主面板时：

LoginWindow panel = new LoginWindow();