Problem making a JProgressBar update values in Loop (Threaded)

java, multithreading, progress-bar, swing, swingworker

Solution

Here's some basis for you to look at, if you can study it and understand why every piece of code is there then I think it will help. Feel free to ask questions in a comment (although I'm going to bed right now!)

Example:

public class ProgressBarDemo extends JFrame {
    private final JProgressBar progressBar = new JProgressBar(0, 100);
    private int progressCounter = 0;

    public ProgressBarDemo() {
        setContentPane(progressBar);
        setPreferredSize(new Dimension(100, 100));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        new Thread(new Runnable() {
            public void run() {
                while (progressCounter <= 100) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            progressBar.setValue(progressCounter++);
                        }
                    });
                    try { Thread.sleep(500); } catch (InterruptedException e) {}
                }
            }
        }).start();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ProgressBarDemo().setVisible(true);
            }
        });
    }
}

Two different ways to approach the problem, using SwingWorker instead:

SwingWorker Example 1:

    ....
    public ProgressBarDemo() {
        setContentPane(progressBar);
        setPreferredSize(new Dimension(100, 100));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();

        SwingWorker<Integer, Void> worker = new SwingWorker<Integer,Void>() {
            public Integer doInBackground() {
                while (progressCounter <= 100) {
                    setProgress(progressCounter++);
                    try { Thread.sleep(500); } catch (InterruptedException e) {}
                }
                return 0;
            }
        };
        worker.addPropertyChangeListener(new PropertyChangeListener() {
            public void propertyChange(PropertyChangeEvent event) {
                if ("progress".equals(event.getPropertyName())) {
                    progressBar.setValue((Integer)event.getNewValue());
                }
            }
        });
        worker.execute();
    }
    ....

SwingWorker Example 2 (not so nice, but interesting nonetheless):

    ....
    public ProgressBarDemo() {
        setContentPane(progressBar);
        setPreferredSize(new Dimension(100, 100));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();

        new SwingWorker<Integer,Integer>() {
            public Integer doInBackground() { 
                while (progressCounter <= 100) {
                    publish(progressCounter++);
                    try { Thread.sleep(500); } catch (InterruptedException e) {}                    
                }
                return 0;
            }
            public void process(List<Integer> progresses) {
                Integer maxProgress = null;
                for (int progress : progresses) {
                    if (maxProgress == null || progress > maxProgress) {
                        maxProgress = progress;
                    }
                }
                progressBar.setValue(maxProgress);
            }
        }.execute();
    }
    ....

Problem

Am trying to get my program to update the progress bar values constantly within a method while performing some operations. However this does not happen until the end, and the UI freezes. After looking around to similar questions with my problems, I tried to implement the accepted solutions (Using threads) however I cannot get it to work correctly. Is just like if they where not there. My program contains several classes, the `Main` being the one automatically created by netbeans on the JFrame Design mode, so there are certain things such as the `static void main` and the `public Main` that am not really sure of some of its contents. Under i will put the snippets of those methods, together with my thread implementation. ``` public class Main extends javax.swing.JFrame implements ActionListener, Runnable{ // I added implements ActLis, Runn..... ... static Main _this; // I included this variable ... public static void main(String args[]) { Main m = new Main(); // Added by me new Thread(m).start(); // Added by me java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new Main().setVisible(true); } }); } ... public Main() { initComponents(); _this = this; // Added by me } ... // I also included these 2 methods in the class public void actionPerformed(ActionEvent e) { synchronized(this){ notifyAll(); } } public void run() { try{synchronized(this){wait();}} catch (InterruptedException e){} progressBar.setValue(50); } ... private void buttonPressed(java.awt.event.MouseEvent evt) { for(int i=0; i<=100; i++) { for(int j=0; j<=5; j++) { // does some work } run(); } } ``` All the things that I commented as `I added...` are things that I putted according to tutorials and answers I have seen online, but nothing seems to work and it feels like I have tried close to a million different combinations... Thanks in advance for helping out.

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