Question

I’m trying to implement a global loading dialog… I want to call some static function to show the dialog and some static function to close it. In the meanwhile I’m doing some work in the main thread or in a sub thread…

I tried following, but the dialog is not updating… Just once at the end, before hiding it again, it updates…

    private static Runnable getLoadingRunable()
{
    if (loadingRunnable != null)
    {
        loadingFrame.setLocationRelativeTo(null);
        loadingFrame.setVisible(true);  
        return loadingRunnable;
    }

    loadingFrame = new JFrame("Updating...");
    final JProgressBar progressBar = new JProgressBar();
    progressBar.setIndeterminate(true);
    final JPanel contentPane = new JPanel();
    contentPane.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
    contentPane.setLayout(new BorderLayout());
    contentPane.add(new JLabel("Updating..."), BorderLayout.NORTH);
    contentPane.add(progressBar, BorderLayout.CENTER);
    loadingFrame.setContentPane(contentPane);
    loadingFrame.pack();
    loadingFrame.setLocationRelativeTo(null);
    loadingFrame.setVisible(true);  

    loadingRunnable = new Runnable() {
        public void run() {

            try {
                while (running) {
                    Thread.sleep(100);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    loadingFrame.setVisible(false);
                }
            });
        }
    };
    return loadingRunnable;
}

public static void showLoadingBar() {
    System.out.println("showLoadingBar");
    running = true;

    threadLoadingBar = new Thread(getLoadingRunable());
    threadLoadingBar.start();
}

public static void hideLoadingBar() {
    System.out.println("hideLoadingBar");
    running = false;
    threadLoadingBar = null;
}

Answer 1

If it doesn’t animate, it means that you’re doing work in the event dispatch thread while the loading frame is displayed. This background work should be done in another thread.

Here’s a non-working example:

public static void main(String[] args) throws Exception {
    SwingUtilities.invokeLater(
        new Runnable() {
            @Override
            public void run() {
                try {
                    showLoadingBar();
                    Thread.sleep(10000L); // doing work in the EDT. Prevents the frame from animating
                    hideLoadingBar();
                }
                catch (InterruptedException e) {
                }
            }
        }
    );
}

Here’s a working example:

public static void main(String[] args) throws Exception {
    showLoadingBar();
    Thread.sleep(10000L); // doing work outside of the EDT. Everything works fine
    hideLoadingBar();
}

Side note: the code which instantiates, populates and makes the loading frame visible should be wrapped into SwingUtilities.invokeLater(), because it must be run in the EDT.