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Thread: Jtable only updates at the end of a buton event.

  1. #1
    Junior Member
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    Apr 2013
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    Default Jtable only updates at the end of a buton event.

    My problem is the following :

    I have a jtable that displays some data in the rows.
    I have a button whose event is to loop slowly through the rows of this table and change the values of the data - in this case flip true/false .. and slowly is due to a sleep (The actual problem I have is a lengthy calculation)
    I would like the table to update after each change, as it currently only updates at the end of the button event.
    What am i doing wrong ? I have tried all sorts of combinations.

    The (self contained) code that demonstrates the problem is below -
    I have adapted the TableDemo example for the orcale/java How to Use Tables tutorial

     * TableDemo is just like SimpleTableDemo, except that it
     * uses a custom TableModel.
    public class TableDemo extends JPanel {
        private JButton looper;
        JTable table;
        MyTableModel mdl;
        private static JFrame frame;
        public TableDemo() {
            super(new GridLayout(2,0));
            looper = new JButton();
            looper.setText("Hit Me to loop thru table and flip vegetarian preference");
            looper.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent evt) {
            mdl = new MyTableModel();       
            table = new JTable(mdl);
            table.setPreferredScrollableViewportSize(new Dimension(500, 70));
            //Create the scroll pane and add the table to it.
            JScrollPane scrollPane = new JScrollPane(table);
            //Add the scroll pane to this panel.
            //add button
        public void HitButtonActionPerformed(ActionEvent e) {
            for (int row=0; row<table.getRowCount();row++)
                try {
                    Thread.currentThread().sleep(1000);//sleep for 1000 ms
                    System.out.println("one more flip");
                    Object p = table.getValueAt(row, 4);
                    table.setValueAt( !((Boolean)p), row, 4);
                    /* no hope
                    ( (AbstractTableModel)table.getModel()).fireTableCellUpdated(row, 4);
                    mdl.fireTableCellUpdated(row, 4);
                } catch (InterruptedException ex) {
                    Logger.getLogger(TableDemo.class.getName()).log(Level.SEVERE, null, ex);
        class MyTableModel extends AbstractTableModel {
            private String[] columnNames = {"First Name",
                                            "Last Name",
                                            "# of Years",
            private Object[][] data = {
            {"Kathy", "Smith","Snowboarding", new Integer(5), false},
            {"John", "Doe","Rowing", new Integer(3), true},
            {"Sue", "Black", "Knitting", new Integer(2), false},
            {"Jane", "White", "Speed reading", new Integer(20), true},
            {"Joe", "Brown","Pool", new Integer(10), false}
            public int getColumnCount() {
                return columnNames.length;
            public int getRowCount() {
                return data.length;
            public String getColumnName(int col) {
                return columnNames[col];
            public Object getValueAt(int row, int col) {
                return data[row][col];
             * JTable uses this method to determine the default renderer/
             * editor for each cell.  If we didn't implement this method,
             * then the last column would contain text ("true"/"false"),
             * rather than a check box.
            public Class getColumnClass(int c) {
                return getValueAt(0, c).getClass();
             * Don't need to implement this method unless your table's
             * editable.
            public boolean isCellEditable(int row, int col) {
                //Note that the data/cell address is constant,
                //no matter where the cell appears onscreen.
                if (col < 2) {
                    return false;
                } else {
                    return true;
             * Don't need to implement this method unless your table's
             * data can change.
            public void setValueAt(Object value, int row, int col) {          
                data[row][col] = value;
                fireTableCellUpdated(row, col);
         * Create the GUI and show it.  For thread safety,
         * this method should be invoked from the
         * event-dispatching thread.
        private static void createAndShowGUI() {
            //Create and set up the window.
            frame = new JFrame("TableDemo");
            //Create and set up the content pane.
            TableDemo newContentPane = new TableDemo();
            newContentPane.setOpaque(true); //content panes must be opaque
            //Display the window.
        public static void main(String[] args) {
            //Schedule a job for the event-dispatching thread:
            //creating and showing this application's GUI.
            javax.swing.SwingUtilities.invokeLater(new Runnable() {
                public void run() {

  2. #2
    Administrator copeg's Avatar
    Join Date
    Oct 2009
    Thanked 833 Times in 772 Posts
    Blog Entries

    Default Re: Jtable only updates at the end of a buton event.

    Use a Thread or a SwingWorker - any long running tasks placed on the EDT will clog up the UI.
    Worker Threads and SwingWorker (The Java™ Tutorials > Creating a GUI With JFC/Swing > Concurrency in Swing)

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