NetBeans jTable不显示

Question

I am relatively new to java and netBeans. I have created table in a database ad want to display this table on a jTable. I have written the following code to do so:

package db_con;

import java.sql.*;
import javax.swing.*;
import net.proteanit.sql.DbUtils;

public class scores extends javax.swing.JPanel {

    Connection conn = null;
    ResultSet re = null;
    PreparedStatement pst = null;
    public scores() {
        initComponents();
        conn = simple.db_connection();
        update_table();
    }

    public void update_table()
    {
        try
        {
            String sql = "SELECT * FROM SINGLE_MATCH";
            pst = conn.prepareStatement(sql);
            re = pst.executeQuery();
            myTable.setModel(DbUtils.resultSetToTableModel(re));
            myTable.getColumnModel().getColumn(0).setPreferredWidth(15);
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null, e);
        }
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        myTable = new javax.swing.JTable();

        myTable.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        jScrollPane1.setViewportView(myTable);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 375, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(15, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(14, Short.MAX_VALUE)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 275, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap())
        );
    }// </editor-fold>                        


    // Variables declaration - do not modify                     
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable myTable;
    // End of variables declaration                   
}

And I am calling this class in the main like so:

new scores().update_table();

But when I run my code the table won't pop up at all. I am getting no errors either, hence the confusion. Any ideas why this could be happening?

Answer 1

Based on you snippets of out-of-context code, it would appear that your either not adding scores to a displayable container, like JFrame or the one you are updating isn't the one which has been added to a displayable container.

Take a look at How to Make Frames (Main Windows) for more details

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Main {

    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                scores theScores = new scores();
                theScores.updateTable();

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(scores);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

You might also like to have a read through Code Conventions for the Java TM Programming Language , it will make it easier for people to read your code and for you to read others