How to add a progress bar?

Maybe I can help you with some example code:

public class SwingProgressBarExample extends JPanel {

  JProgressBar pbar;

  static final int MY_MINIMUM = 0;

  static final int MY_MAXIMUM = 100;

  public SwingProgressBarExample() {
    // initialize Progress Bar
    pbar = new JProgressBar();
    pbar.setMinimum(MY_MINIMUM);
    pbar.setMaximum(MY_MAXIMUM);
    // add to JPanel
    add(pbar);
  }

  public void updateBar(int newValue) {
    pbar.setValue(newValue);
  }

  public static void main(String args[]) {

    final SwingProgressBarExample it = new SwingProgressBarExample();

    JFrame frame = new JFrame("Progress Bar Example");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(it);
    frame.pack();
    frame.setVisible(true);

    // run a loop to demonstrate raising
    for (int i = MY_MINIMUM; i <= MY_MAXIMUM; i++) {
      final int percent = i;
      try {
        SwingUtilities.invokeLater(new Runnable() {
          public void run() {
            it.updateBar(percent);
          }
        });
        java.lang.Thread.sleep(100);
      } catch (InterruptedException e) {
        ;
      }
    }
  }
}

Your question is a bit vague, but it sounds to me like you want the progress bar to show progress for a specific running method, which I'll call the "work()" method. Unfortunately, there's no way to just pass a reference to your method to a progress bar - your method needs to explicitly tell the progress bar what to display. Here's what I would do:

1. Make the progress bar's reference available to work() - either pass it in as an argument to work(), or provide an accessor method that your code in work() can call to get a reference to the progress bar.

2. Inside work(), after you've obtained a reference to the progress bar (which I'll call "pb", call pb.setMinimum(0) and pb.setMaximum(n) where n is the number of steps your method has to get through.

3. As your method completes each step, call pb.setValue(pb.getValue()+1);

4. At the end of your method, call pb.setValue(0); to reset the progress bar prior to returning.

Also, if you want your progress bar to display a String message, you first have to call pb.setStringPainted(true), then subsequent calls to pb.setString(string) will show up on the progress bar.

See my answer on another SO question which includes an example of a JProgressBar which gets updated by using a SwingWorker. The SwingWorker is used to execute a long running task in the background (in case of the example it is just a regular Thread.sleep) and report on progress at certain intervals.

I would also strongly suggest to take a look at the Swing concurrency tutorial for more background info on why you should use a SwingWorker when performing long-running tasks which interfere with the UI.

A similar example as the one I posted is available in the Swing tutorial about JProgressBars, which it also worth looking at