Question

I have a multi threaded program and I’m trying to use a JTable to view the progress of each thread. Each thread is a row the JTable. I have posted a simplified and relevant code of what I have now. Each time I press start a new thread is started and the row is added to the JTable. But how do I update the “Column 2” which of the row which belongs to that thread from the running thread?

In main this is what I have

JTable table = new JTable(new DefaultTableModel(new Object[]{"Thread Name", "Progress"}, 0));

btnBegin.addActionListener(new ActionListener()
{
  public void actionPerformed(ActionEvent arg0)
  {
    Thread newThread = new Thread(new MyThreadClass(country, category));
    newThread.start();
    DefaultTableModel model = (DefaultTableModel) table.getModel();
    model.addRow(new Object[]{"Thread " + threadNumber, "Column 2"});
  }
});

Answer 1

If you can add a field tableModel to MyThreadClass (field+constructor argument), from this class, you can invoke the code @sedran was mentioning.

Example:

public class T {

static int threadNumber = 0;

public static void main(String[] args) throws Exception {

    final JTable table = new JTable(new DefaultTableModel(new Object[] { "Thread Name", "Progress" }, 0));

    JButton btnBegin = new JButton("Begin");
    btnBegin.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent arg0) {
            DefaultTableModel model = (DefaultTableModel) table.getModel();
            MyThreadClass newThread = new MyThreadClass(model, threadNumber++);
            newThread.start();

            model.addRow(new Object[] { "Thread " + threadNumber, "Column 2" });
        }
    });

    JFrame frame = new JFrame();
    frame.add(btnBegin, BorderLayout.NORTH);
    frame.add(table);
    frame.setSize(400, 400);
    frame.setVisible(true);
}

static class MyThreadClass extends Thread {
    private final DefaultTableModel model;
    private final int threadNumber;

    public MyThreadClass(DefaultTableModel model, int threadNumber) {
        super();
        this.model = model;
        this.threadNumber = threadNumber;
    }

    @Override
    public void run() {
        for (int i = 0; i <= 5; i++) {
            final int index = i;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            SwingUtilities.invokeLater(new Runnable() {

                @Override
                public void run() {
                    model.setValueAt(index * 20, threadNumber, 1);
                }
            });
        }
    }
}

}

Please note that the use of SwingUtilities.invokeLater is important as the view MUST be refreshed in the EDT.