使用 Rob Camick 的 ListTableModel，但 JTable 没有显示

Question

我正在使用 Camick 的 ListTableModel 和 RowTableModel 从这里 http://tips4java.wordpress.com/2009/03/12/table-from-database/

但是，JTable 没有显示。有谁知道为什么？我没有收到任何错误。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;

public class AddressBook {

    JLabel name, address, phone, email;
    JTextField nameField, addressField, phoneField, emailField;
    JButton addPerson, addEntry, cancelEntry;
    JTable table;
    ListTableModel model;
    JDialog addEntryDialog;
    String[] headings = {"Name", "Address", "Phone #", "Email"};

    AddressBook() {
        try {
            Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
        } catch (ClassNotFoundException e) {
            System.out.println(e);
        }

        try {
            Connection con = DriverManager.getConnection("jdbc:derby://localhost:1527/AddressBook", "addressbook", "addressbook");
            Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);

            ResultSet rs = stmt.executeQuery("SELECT * FROM APP.ADDRESSBOOK");
            ListTableModel model = ListTableModel.createModelFromResultSet(rs);

            rs.close();
            //resultset.close();
            stmt.close();
            con.close();

        } catch(SQLException e){
            System.err.println(e);
        }

        JFrame frame = new JFrame("Address Book");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);
        frame.getContentPane().setLayout(new FlowLayout());

        ButtonListener listener = new ButtonListener();

        addPerson = new JButton("New Entry");
        addPerson.addActionListener(listener);

        table = new JTable(model);
        JScrollPane scroll = new JScrollPane(table);
        scroll.setPreferredSize(new Dimension(500, 490));

        //Add a person Dialog

        name = new JLabel("Name:");
        address = new JLabel("Address:");
        phone = new JLabel("Phone:");
        email = new JLabel("Email:");

        nameField = new JTextField(8);
        addressField = new JTextField(8);
        phoneField = new JTextField(8);
        emailField = new JTextField(8);

        addEntry = new JButton("Save");
        addEntry.addActionListener(listener);
        cancelEntry = new JButton("Cancel");
        cancelEntry.addActionListener(listener);

        addEntryDialog = new JDialog(frame, "Add a Person");
        addEntryDialog.setSize(190, 300);
        addEntryDialog.getContentPane().setLayout(new FlowLayout());

        addEntryDialog.getContentPane().add(name);
        addEntryDialog.getContentPane().add(nameField);
        addEntryDialog.getContentPane().add(address);
        addEntryDialog.getContentPane().add(addressField);
        addEntryDialog.getContentPane().add(phone);
        addEntryDialog.getContentPane().add(phoneField);
        addEntryDialog.getContentPane().add(email);
        addEntryDialog.getContentPane().add(emailField);
        addEntryDialog.getContentPane().add(cancelEntry);
        addEntryDialog.getContentPane().add(addEntry);

        //end of Add a person dialog

        frame.getContentPane().add(addPerson);
        frame.getContentPane().add(table);
        frame.setVisible(true);
    }

    class ButtonListener implements ActionListener {

        public void actionPerformed(ActionEvent event) {
            JButton source = (JButton) event.getSource();

            if (source == addPerson) {
                addEntryDialog.setVisible(true);
            }
            if (source == addEntry) {
                //add to db
            }
            if (source == cancelEntry) {
                addEntryDialog.setVisible(false);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                new AddressBook();
            }
        });
    }
}

Answer 1

再看一下您的代码，问题在于您已将“模型”变量定义为类变量和实例变量。实例变量包含来自 ResultSet 的数据。用于创建表的类变量为 null。代码应该是：

//ListTableModel model = ListTableModel.createModelFromResultSet(rs); 
model = ListTableModel.createModelFromResultSet(rs); 

Answer 2

好吧，您将其添加到滚动窗格，而不是将滚动窗格添加到内容窗格。您只是添加表格。

如果没有滚动窗格，您将不会有任何列标题。如果没有任何数据，表的首选大小是否为 0x0？

    frame.getContentPane().add(addPerson); 
    frame.getContentPane().add(**scroll**); 
    frame.setVisible(true);