JProgressBar Doesn't Start Until Try-catch finishes

Question

I am writing a program which uses Random.ORG api. When I click calculate button, JProgressBar starts right after the opeartion is being done and stay freezed until this moment.

I tried extra try-catch clauses, if statements and bool-gates. None of them worked, how could I fix it?

kazananiBelirleButon.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                progressBar.setVisible(true);
                progressBar.setIndeterminate(true);

                try {

                    HashMap<String, Object> randoms = randSonuc.generateSignedIntegers(5, 0, 10);
                    System.out.println(randoms.toString());
                    String test = randoms.toString().substring(randoms.toString().indexOf("{r")+1, randoms.toString().indexOf(", da")).replace("random=", "{\"random\":") + "}";


                    System.out.println(tarihiYazdir(test,14));
                    cekilisTarihiTextPane.setText(tarihiYazdir(test,2).toString());
                    sonucPane.setText("\n"+sonuclariYazdir(test,0));



                } catch (RandomOrgSendTimeoutException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (RandomOrgKeyNotRunningError e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (RandomOrgInsufficientRequestsError e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (RandomOrgInsufficientBitsError e1) {
                    System.out.print("lol");
                    e1.printStackTrace();
                } catch (RandomOrgBadHTTPResponseException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (RandomOrgRANDOMORGError e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (RandomOrgJSONRPCError e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (MalformedURLException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
        });

Answer 1

Swing is single threaded. Calling listeners, painting/updating UI all happen on a single thread called the Event Dispatch Thread (EDT).

Since you do all your work in the event handler code, the Swing UI cannot be updated until you return from your method (actionPerformed()).

Read this tutorial: Concurrency in Swing

What you should do is do your time-consuming work in a separate thread and only do short tasks in the EDT (e.g. UI updates).

Also check out the SwingWorker class which is designed to perform lengthy GUI-interaction tasks in a background thread.

Answer 2

Try using swing worker in your method. Swing Worker

Here is an example from old version of swing worker. Firs you need to add SwingWorker class to your project:

import javax.swing.SwingUtilities;

/**
 * This is the 3rd version of SwingWorker (also known as
 * SwingWorker 3), an abstract class that you subclass to
 * perform GUI-related work in a dedicated thread.  For
 * instructions on using this class, see:
 *
 * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
 *
 * Note that the API changed slightly in the 3rd version:
 * You must now invoke start() on the SwingWorker after
 * creating it.
 */
public abstract class SwingWorker
{

    private Object value;  // see getValue(), setValue()
    private Thread thread;

    /**
     * Class to maintain reference to current worker thread
     * under separate synchronization control.
     */
    private static class ThreadVar
    {

        private Thread thread;

        ThreadVar(Thread t)
        {
            thread = t;
        }

        synchronized Thread get()
        {
            return thread;
        }

        synchronized void clear()
        {
            thread = null;
        }
    }
    private ThreadVar threadVar;

    /**
     * Get the value produced by the worker thread, or null if it
     * hasn't been constructed yet.
     */
    protected synchronized Object getValue()
    {
        return value;
    }

    /**
     * Set the value produced by worker thread
     */
    private synchronized void setValue(Object x)
    {
        value = x;
    }

    /**
     * Compute the value to be returned by the <code>get</code> method.
     */
    public abstract Object construct();

    /**
     * Called on the event dispatching thread (not on the worker thread)
     * after the <code>construct</code> method has returned.
     */
    public void finished()
    {
    }

    /**
     * A new method that interrupts the worker thread.  Call this method
     * to force the worker to stop what it's doing.
     */
    public void interrupt()
    {
        Thread t = threadVar.get();
        if (t != null)
        {
            t.interrupt();
        }
        threadVar.clear();
    }

    /**
     * Return the value created by the <code>construct</code> method.
     * Returns null if either the constructing thread or the current
     * thread was interrupted before a value was produced.
     *
     * @return the value created by the <code>construct</code> method
     */
    public Object get()
    {
        while (true)
        {
            Thread t = threadVar.get();
            if (t == null)
            {
                return getValue();
            }
            try
            {
                t.join();
            }
            catch (InterruptedException e)
            {
                Thread.currentThread().interrupt(); // propagate
                return null;
            }
        }
    }

    /**
     * Start a thread that will call the <code>construct</code> method
     * and then exit.
     */
    public SwingWorker()
    {
        final Runnable doFinished = new Runnable()
        {

            public void run()
            {
                finished();
            }
        };

        Runnable doConstruct = new Runnable()
        {

            public void run()
            {
                try
                {
                    setValue(construct());
                }
                finally
                {
                    threadVar.clear();
                }

                SwingUtilities.invokeLater(doFinished);
            }
        };

        Thread t = new Thread(doConstruct);
        threadVar = new ThreadVar(t);
    }

    /**
     * Start the worker thread.
     */
    public void start()
    {
        Thread t = threadVar.get();
        if (t != null)
        {
            t.start();
        }
    }
}

Then add your logic inside:

SwingWorker worker = new SwingWorker() {
    @Override
    public Object construct() {
        // add your code here
        progressBar.setVisible(true);
        progressBar.setIndeterminate(true);
        // and so on...

        return 0;
    }
};
worker.start();

So the end resuld should look like this (Note that this is untested code):

kazananiBelirleButon.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                SwingWorker worker = new SwingWorker() {

                    @Override
                    public Object construct() {
                        progressBar.setVisible(true);
                        progressBar.setIndeterminate(true);

                        try {

                            HashMap<String, Object> randoms = randSonuc.generateSignedIntegers(5, 0, 10);
                            System.out.println(randoms.toString());
                            String test = randoms.toString().substring(randoms.toString().indexOf("{r")+1, randoms.toString().indexOf(", da")).replace("random=", "{\"random\":") + "}";

                            System.out.println(tarihiYazdir(test,14));
                            cekilisTarihiTextPane.setText(tarihiYazdir(test,2).toString());
                            sonucPane.setText("\n"+sonuclariYazdir(test,0));

                        } catch (RandomOrgSendTimeoutException e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (RandomOrgKeyNotRunningError e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (RandomOrgInsufficientRequestsError e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (RandomOrgInsufficientBitsError e1) {
                            System.out.print("lol");
                            e1.printStackTrace();
                        } catch (RandomOrgBadHTTPResponseException e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (RandomOrgRANDOMORGError e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (RandomOrgJSONRPCError e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (MalformedURLException e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        } catch (IOException e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        }
                    }
                     return 0;
                }
            };
            worker.start();
        });