Java - Progress Bar Not Progressing

Question

All the coding runs, my only problem is that the progress bar doesn't display the value changes. I set the values, but if I run it the value set, doesn't display on the progress bar. (The bar doesn't fill up)

public void logIn() {
    try {
        while (true) {
            calculate();
            System.out.println(loadingProgress);
            if (loadingProgress < 100) {
                mGUI.pbLoading.setValue(loadingProgress);
                Thread.sleep(random.nextInt(5000) + 100);
            } else {
                mGUI.pbLoading.setValue(100);
                break;
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public void calculate() {
    random = new Random();
    loadingProgress = loadingProgress + random.nextInt(9) + 1;
}

Seems here you block `EDT`. Read [Concurrency in Swing](https://docs.oracle.com/javase/tutorial/uiswing/concurrency/), also you need to use [`SwingWorker`](https://docs.oracle.com/javase/tutorial/uiswing/concurrency/simple.html) for long background task. Examine that [example](http://stackoverflow.com/a/15710912/2894369). — alex2410, May 05 '15 at 09:09
Exactly the [same situation I faced](http://stackoverflow.com/questions/29727991/jprogressbar-does-not-update-within-the-loop). [Here](http://stackoverflow.com/questions/29817219/changing-the-default-cursor-to-busy-cursor-does-not-work-as-expected) is the fixed code. Use a SwingWorker. — Spikatrix, May 05 '15 at 11:22

derMrich · Accepted Answer · 2015-05-05T09:28:11.663

0

The calculation has to be done in an extra thread. This is because the currently running thread is blocking the repaint of the UI until the calculation is done.

edited May 05 '15 at 09:28

answered May 05 '15 at 09:10

derMrich

316
4
12

2

No, not really, the progress bar needs to be updated on the EDT, otherwise you violate the single thread nature of the api. The work needs to be done on a separate thread, so as not to block the EDT – MadProgrammer May 05 '15 at 09:14
Yes, you are right, i confused both and will update my post. – derMrich May 05 '15 at 09:27

score 0 · Answer 2 · answered May 05 '15 at 09:15

The problem is outside your posted code. I used your code to create a working example:

package snippet;

import java.util.Random;

public class Snippet {
    public class ValueAccepter {

        public void setValue(int loadingProgress) {
            System.out.println(loadingProgress);
        }

    }

    public class MGUI {

        public final ValueAccepter pbLoading = new ValueAccepter();

    }

    private int loadingProgress;
    private Random random;
    private MGUI mGUI = new MGUI();

    public static void main(String[] args) {
        new Snippet().logIn();
    }

    public void logIn() {
        try {
            while (true) {
                calculate();
                System.out.println(loadingProgress);
                if (loadingProgress < 100) {
                    mGUI.pbLoading.setValue(loadingProgress);
                    Thread.sleep(random.nextInt(5000) + 100);
                } else {
                    mGUI.pbLoading.setValue(100);
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void calculate() {
        random = new Random();
        loadingProgress = loadingProgress + random.nextInt(9) + 1;
    }
}

I think you have a problem with your swing-threads. Make sure, that mGUI.pbLoading.setValue is returning as expected.

No, it's not. The login method is been executed within the context of the EDT, where as yours isn't, violating the single thread rules of Swing — MadProgrammer, May 05 '15 at 09:19
@MadProgrammer You are right, if `pbLoading` is a Swing Component. In my example pbLoading is not a Swing Component - and everything works fine. If we had more code of Francois, we could tell whether the thread rules are violated. — slartidan, May 05 '15 at 10:23

BullyWiiPlaza · Answer 3 · 2015-05-05T09:30:26.187

0

You have to use SwingWorker to execute graphical user interface operations and calculations otherwise the event dispatch thread won't be able to repaint. Here is a progress bar demo code by Oracle.

edited May 05 '15 at 09:30

answered May 05 '15 at 09:19

BullyWiiPlaza

17,329
10
113
185

You don't "have" to, but it is probably the preferred method. But if I were the op, I'd be asking why? Which you've not explained – MadProgrammer May 05 '15 at 09:21

Java - Progress Bar Not Progressing

3 Answers3