Java Swing注册页与主页窗口连接问题求助

开发适配特殊发票机的发票系统，采用JavaFX结合Swing技术。已完成连接SQLite数据库的注册页面（Invoice1.java），关联注册页与主页（Home.java）时出现异常：

• 点击注册页「创建账户」按钮，弹出「账户已创建」提示框；点击提示框「OK」后，注册页面板被隐藏，但弹出的主页窗口为空白。
• 要求手动编码实现页面跳转，禁止使用JForms（项目将其视为低代码）。

现有代码 #

Invoice1.java #

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package invoice1;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
 *
 * @author kate3
 */

public class Invoice1 extends Home {
    private static JLabel nameLabel;
    private static JTextField nameText;
    private static JLabel passwordLabel;
    private static JTextField passwordText;
    private static JButton button;
   
    /**
     * @param args the command line arguments
     */
 
    public static void main(String[] args) {
       
            /*Creating  the signup form, part of code used from: https://www.youtube.com/watch?v=iE8tZ0hn2Ws) 
            */ 
                JPanel panel = new JPanel();
                JFrame frame = new JFrame();
                frame.setSize(350, 200);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(panel);
                                
                panel.setLayout(null);
                
                nameLabel = new JLabel("Business Name");
                nameLabel.setBounds(10, 20, 80, 25);
                panel.add(nameLabel);
                
                nameText = new JTextField(40);
                nameText.setBounds(100, 20, 165, 25);
                panel.add(nameText);
                
                passwordLabel = new JLabel ("Create Password");
                passwordLabel.setBounds (10, 50, 80, 25);
                panel.add(passwordLabel);
                
                passwordText = new JTextField(20);
                passwordText.setBounds(100, 50, 165, 25);
                panel.add(passwordText);
               
                button = new JButton("Create Account");
                button.setBounds(130, 110, 80, 25);
                        frame.setVisible(true);
                button.addActionListener(new ActionListener(){
                    
                    @Override
                    public void actionPerformed(ActionEvent e){
                        String name = nameText.getText();
                        String password = passwordText.getText();
                        addToDB(name, password);
                        
                        
                        JOptionPane.showMessageDialog(frame, "Account Created!");
                        panel.setVisible(false);
                        Home.setVisible(true);
                    }
                });
                panel.add(button);
                frame.setVisible(true);
    }
    
    
    
    
    /* keeping in file in case needed in future
    
    public void buttonPerformed(ActionEvent e) {
        String name = nameText.getText();
        String password = passwordText.getText();
        
        if(name.equals("kate") && password.equals("password")){
            successful.setText("Login successful!");
        }
      
    }*/
    
    //adding data inputted to database
    public static void addToDB ( String un, String pass){
            Connection dbCon = null;
        
        String strUrl = "jdbc:sqlite:testDB.db";
        try{
            dbCon = DriverManager.getConnection(strUrl, "root", "root");
            System.out.println("Connected");
            
              Statement st = dbCon.createStatement();
              
              PreparedStatement stmt = dbCon.prepareStatement("Select * From loginDetails");
                st.executeUpdate("insert into loginDetails (username, password)"
                    + " values ('" + un + "' , '" + pass + "')");
                
            ResultSet rs = stmt.executeQuery();
            while(rs.next()){
                System.out.println(rs.getString(1));
                System.out.println(rs.getString(2));
            }
            
            
        }catch(SQLException e){
        
    }

}
  /*
    @Override
    public void actionPerformed(ActionEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
*/
 }

Home.java #

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package invoice1;

import java.awt.PopupMenu;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

/**
 *
 * @author kate3
 */
public class Home {
    private static JLabel homeLabel ;
    private static JButton invoiceButton;
    private static JButton invoiceHistory;
    private static JButton statementButton;
    private static JButton statementHistory;
    private static JButton productButton;
    private static JButton customerButton;
    
    
    public static void main(String[] args) {
        JPanel home = new JPanel();
        
        //linking Invoice1 JFrame
        Home.getInvoice1();
        
       // frame.setSize(350, 200);
        Home.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        home.setLayout(null);
        
        homeLabel = new JLabel("HOME");
        homeLabel.setBounds(100, 20, 80, 25);
        home.add(homeLabel);
        
        invoiceButton = new JButton("Create Invoice");
        invoiceButton.setBounds(100, 50, 80, 25);
        home.add(invoiceButton);
        
        statementButton = new JButton("Create Statement");
        statementButton.setBounds(100, 80, 80, 25);
        home.add(statementButton);
        
        invoiceHistory = new JButton("Invoice History");
        invoiceHistory.setBounds(100, 80, 80, 25);
        home.add(invoiceHistory);
        
        statementHistory = new JButton("Statement History");
        statementHistory.setBounds(100, 140, 80, 25);
        home.add(statementHistory);
        
        productButton = new JButton("Products");
        productButton.setBounds(100, 170, 80, 25);
        home.add(productButton);
        
        customerButton = new JButton("Customers");
        customerButton.setBounds(100, 200, 80, 25);
        home.add(customerButton);
        
        Home.setVisible(true);
    }

    private static void setDefaultCloseOperation(int EXIT_ON_CLOSE) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    static class Invoice1 extends Home {

        PopupMenu Invoice1;

        public Invoice1() {
        }
    }

    static void setVisible(boolean b) {
    }

    
    private static void getInvoice1() {
    }
    
}

问题根源 #

1. Home类结构错误：Home并非JFrame子类，没有实际创建窗口实例，静态方法setVisible为空实现，调用Home.setVisible(true)无法显示有效窗口。
2. 继承关系混乱：Invoice1继承Home无实际意义，且注册页仅隐藏面板而非关闭窗口。
3. SQL语句风险：注册数据插入采用字符串拼接，存在SQL注入风险。

修改后的代码 #

Home.java #

package invoice1;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Home extends JFrame {
    private JLabel homeLabel ;
    private JButton invoiceButton;
    private JButton invoiceHistory;
    private JButton statementButton;
    private JButton statementHistory;
    private JButton productButton;
    private JButton customerButton;
    
    public Home() {
        // 初始化窗口属性
        setTitle("Invoice System - Home");
        setSize(400, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null); // 居中显示
        
        JPanel homePanel = new JPanel();
        homePanel.setLayout(null);
        add(homePanel);
        
        // 添加主页组件
        homeLabel = new JLabel("HOME");
        homeLabel.setBounds(150, 20, 80, 25);
        homePanel.add(homeLabel);
        
        invoiceButton = new JButton("Create Invoice");
        invoiceButton.setBounds(120, 50, 150, 25);
        homePanel.add(invoiceButton);
        
        statementButton = new JButton("Create Statement");
        statementButton.setBounds(120, 80, 150, 25);
        homePanel.add(statementButton);
        
        invoiceHistory = new JButton("Invoice History");
        invoiceHistory.setBounds(120, 110, 150, 25);
        homePanel.add(invoiceHistory);
        
        statementHistory = new JButton("Statement History");
        statementHistory.setBounds(120, 140, 150, 25);
        homePanel.add(statementHistory);
        
        productButton = new JButton("Products");
        productButton.setBounds(120, 170, 150, 25);
        homePanel.add(productButton);
        
        customerButton = new JButton("Customers");
        customerButton.setBounds(120, 200, 150, 25);
        homePanel.add(customerButton);
    }
    
    public static void main(String[] args) {
        // 启动主页
        new Home().setVisible(true);
    }
}

Invoice1.java #

package invoice1;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Invoice1 {
    private static JLabel nameLabel;
    private static JTextField nameText;
    private static JLabel passwordLabel;
    private static JTextField passwordText;
    private static JButton button;
    private static JFrame frame; // 保存注册窗口实例
    
    public static void main(String[] args) {
        frame = new JFrame("Create Account");
        frame.setSize(350, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        
        JPanel panel = new JPanel();
        panel.setLayout(null);
        frame.add(panel);
        
        nameLabel = new JLabel("Business Name");
        nameLabel.setBounds(10, 20, 80, 25);
        panel.add(nameLabel);
        
        nameText = new JTextField(40);
        nameText.setBounds(100, 20, 165, 25);
        panel.add(nameText);
        
        passwordLabel = new JLabel ("Create Password");
        passwordLabel.setBounds (10, 50, 80, 25);
        panel.add(passwordLabel);
        
        passwordText = new JTextField(20);
        passwordText.setBounds(100, 50, 165, 25);
        panel.add(passwordText);
       
        button = new JButton("Create Account");
        button.setBounds(130, 110, 120, 25);
        button.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e){
                String name = nameText.getText();
                String password = passwordText.getText();
                
                if (name.isEmpty() || password.isEmpty()) {
                    JOptionPane.showMessageDialog(frame, "Please fill all fields");
                    return;
                }
                
                if (addToDB(name, password)) {
                    JOptionPane.showMessageDialog(frame, "Account Created!");
                    // 关闭注册窗口，启动主页
                    frame.dispose();
                    new Home().setVisible(true);
                } else {
                    JOptionPane.showMessageDialog(frame, "Failed to create account");
                }
            }
        });
        panel.add(button);
        frame.setVisible(true);
    }
    
    // 插入数据到数据库，返回操作结果
    public static boolean addToDB(String un, String pass){
        Connection dbCon = null;
        String strUrl = "jdbc:sqlite:testDB.db";
        
        try{
            dbCon = DriverManager.getConnection(strUrl); // SQLite无需用户名密码
            System.out.println("Connected to database");
            
            // 使用PreparedStatement防止SQL注入
            String insertSql = "INSERT INTO loginDetails (username, password) VALUES (?, ?)";
            PreparedStatement stmt = dbCon.prepareStatement(insertSql);
            stmt.setString(1, un);
            stmt.setString(2, pass);
            
            int affectedRows = stmt.executeUpdate();
            return affectedRows > 0;
            
        }catch(SQLException e){
            e.printStackTrace();
            return false;
        } finally {
            try {
                if (dbCon != null) dbCon.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

修改说明 #

1. Home类重构：改为继承JFrame，在构造方法中完成窗口和组件初始化，确保调用new Home().setVisible(true)能显示完整主页。
2. 注册页优化：移除不必要的继承关系，保存注册窗口实例，注册成功后直接关闭窗口并启动主页。
3. 数据库操作优化：使用PreparedStatement替代字符串拼接，避免SQL注入风险，同时返回操作结果以便判断注册是否成功。
4. 用户体验提升：增加空字段校验，窗口居中显示，按钮尺寸调整更合理。

内容的提问来源于stack exchange，提问作者Kate Murphy