Refreshing data in a JTable

[Chris Brandon]

Hi All

I am quite new to Java and have been trying to learn a bit about JTables for a project I want to undertake. I have created a new JFrame in netbeans and added a button. Onclicking the button I want add some data to a JTable model and then output the JTable with the data. When I click the button again I want the same process to happen again and overwrite the previous table being displayed.

I have written the following code below:

import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;


public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        initComponents();
    }

    /**
     * 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() {

        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jButton1)
                .addContainerGap(529, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(22, 22, 22)
                .addComponent(jButton1)
                .addContainerGap(423, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    
    model = new DefaultTableModel();
    outputTable = new JTable();
    //outputTable.setModel(model);
    
   model.setRowCount(0);
   model.setColumnCount(0);
     
   System.out.println("Counter = " + counter);
    if(counter > 0)
    {
        
      
     model.addColumn("Description");
     model.addColumn ("From");
     model.addColumn ("To");
     model.addColumn ("Message Type");
     model.addColumn ("Area");
        
     model.addRow(new Object[]{"1","2","2","3","6"});
     model.addRow(new Object[]{"54","5","5","5","6"});
     model.addRow(new Object[]{"","","","",""});
     model.addRow(new Object[]{"","","","",""});
     model.addRow(new Object[]{"","","","",""});
     
     Object value = model.getValueAt(1,0);
     System.out.println(value);
        
     System.out.println("Should be Normal headings");
    
    }
    else
    {
      model.addColumn("2");
      model.addColumn ("2");
      model.addColumn ("2");
      model.addColumn ("2");
      model.addColumn ("2");
        
        
      model.addRow(new Object[]{"","","","",""});
      model.addRow(new Object[]{"","","","",""});
      model.addRow(new Object[]{"","","","",""});
      model.addRow(new Object[]{"","","","",""});
      model.addRow(new Object[]{"","","","",""});
        
     Object value = model.getValueAt(1,0);
     System.out.println(value);
     System.out.println("Should be number headings");
        
    }
    
    outputTable.setModel(model);
    outputTable.setBackground(Color.white);
    outputTable.setAlignmentX(50);
    outputTable.setAlignmentY(150);
    
    outputTable.setMinimumSize(new Dimension(300,300));
    outputTable.setSize(500,500);
    tableScrollPane = new JScrollPane(outputTable);
    tableScrollPane.setSize(500, 500);
    tableScrollPane.setLocation(50, 150); 
     
    this.add(tableScrollPane);
     
    counter ++;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * Set the Nimbus look and feel
         */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the
         * default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    // End of variables declaration
    JTable outputTable;
    JScrollPane tableScrollPane;
    int counter = 0;
    DefaultTableModel model;


}

The problem I have is that when I click the button for a second time the table stays on the screen exactly as it did following the first click. I can see that the data in the model is changing so I am not sure why a new JTable is not drawn. Can anyone shed any light on where I am going wrong?

Thanks.

Chris.

[Campbell Ritchie]

Welcome to the Ranch

I know precious little about JTables myself, but have you checked the Java Tutorials? I don't know whether the parts about data listeners and change listeners will help you.

We usually discuss tables in the GUIs forum; I shall move you there.

[Stevens Miller]

Looks to me like each button click is creating a new default table model at Line 59, and installing it into the table at Line 110. That's always going to result in the code from Lines 91 through 102 being run once for each new table you create upon each click of the button, with the end result being you are getting an identical (albeit new) table each time.

[Chris Brandon]

Thanks Stevens Miller. That solved my problem perfectly!

[Stevens Miller]

Glad to help. Good luck with whatever you are doing.