JProgressBar not working properly

Question

So my JProgressBar I have set up doesn\'t work the way I want it. So whenever I run the program it just goes from 0 to 100 instantly. I tried using a Prog

Answer 1

Swing is a single threaded environment, that is, there is a single thread which is responsible for processing all the events that occur within the system, including repaint events. Should anything block this thread for any reason, it will prevent Swing from processing any new events, including, repaint events...

So all this ...

EventQueue.invokeLater(new Runnable() {
    @Override
    public void run() {
        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            Logger.getLogger(BandListGenerator.class.getName()).log(Level.SEVERE, null, ex);        }
        jProgressBar2.setValue(progress);
    }
});

Is constantly pausing the Event Dispatching Thread, preventing it from actually doing any updates (or at least spacing them randomly)...

It's also likely that your outer loop is been run from within the context of the EDT, meaning that until it exists, nothing in the Event Queue will be processed. All your repaint requests will be consolidated down to a single paint request and voila, instant filled progress bar...

You really should use a SwingWorker - I know you said you tried one, but you've not shown any code as to your attempt in this regards, so it's difficult to know why it didn't work, however...

• SwingWorker and JProgressBar example
• SwingWorker and JProgressBar example
• SwingWorker and JProgressBar example
• SwingWorker and JProgressBar example
• SwingWorker and dual welding JProgressBar example
• SwingWorker and JProgressBar example

And forgive me if we haven't said this a few times before :P

Answer 2

You are evoking Thread.sleep inside the EvokeLater which means that it is running on another thread than your for loop. i.e., your for loop is completing instantaneously (well, however long it takes to loop from 1 to 100, which is almost instantaneously).

Move Thread.sleep outside of EvokeLater and it should work as you intend.

    int max = 10;
    for (int i = 0; i <= max; i++) {
        final int progress = (int)Math.round(
            100.0 * ((double)i / (double)max)
        );

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                jProgressBar2.setValue(progress);
            }
        });
        try {
            Thread.sleep(1000);
        } catch (InterruptedException ex) {
            Logger.getLogger(BandListGenerator.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

Edit: agree with @MadProgrammer. It appears this is just an illustrative question, but you should make sure whatever you're trying to accomplish here you use a SwingWorker for.