Show an indeterimante progress bar in a JDialog in a thread and run a task in another thread concurrently

Question

When a user clicks a button, a long task of approximately 10 seconds will run. During this time I want to show a progress bar to the user. But the main thread has to wait for the worker thread to finish because the worker thread will set a variable that the main thread will use. If I don't wait the worker thread I will get a NullPointerException when using the variable. So after the worker thread finishes, I will also close the progress bar dialog.

When I wait for the worker thread using join() the progress bar dialog shows (interestingly without the progress bar though) and hangs there.

Thread runnable = new Thread() {

    public void run() {
        try {
            System.out.println("thread basladi");
            threadAddSlaveReturnMessage = request.addSlave(
                ipField.getText(), passField.getText(), 
                nicknameField.getText());
            System.out.println("thread bitti");

        } catch (LMCTagNotFoundException e) {
            e.printStackTrace();
        }

    }
};

Thread runnable_progress = new Thread() {

    public void run() {

        JTextArea msgLabel;
        JDialog dialog;
        JProgressBar progressBar;
        final int MAXIMUM = 100;
        JPanel panel;

        progressBar = new JProgressBar(0, MAXIMUM);
        progressBar.setIndeterminate(true);
        msgLabel = new JTextArea("deneme");
        msgLabel.setEditable(false);


        panel = new JPanel(new BorderLayout(5, 5));
        panel.add(msgLabel, BorderLayout.PAGE_START);
        panel.add(progressBar, BorderLayout.CENTER);
        panel.setBorder(BorderFactory.createEmptyBorder(11, 11, 11, 11));

        dialog = new JDialog(Frame.getFrames()[0], "baslik", true);
        dialog.getContentPane().add(panel);
        dialog.setResizable(false);
        dialog.pack();
        dialog.setSize(500, dialog.getHeight());
        dialog.setLocationRelativeTo(null);
        dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
        dialog.setAlwaysOnTop(false);
        dialog.setVisible(true);
        msgLabel.setBackground(panel.getBackground());
    }
};

runnable.start();
System.out.println("runnable start");
runnable_progress.start();
System.out.println("progress start");
runnable.join();
System.out.println("runnable join");
runnable_progress.join();
System.out.println("progress join");


if (threadAddSlaveReturnMessage.equalsIgnoreCase("OK")) {
    fillInventoryTable(inventoryTable);
    JOptionPane.showMessageDialog(this, messages.getString("centrum.addslavepanel.SUCCESS"), null, JOptionPane.INFORMATION_MESSAGE);
}

"progress join"

doesn't get printed.

Answer 1

You can use a SwingWorker here. A short example :

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package org.godel.nio;

import java.awt.BorderLayout;
import java.util.List;
import javax.swing.*;

/**
 *
 * @author internet_2
 */
public class Test {

    public static void main(String[] args) {
        new Test().doJob();
    }

    public void doJob() {

        JTextArea msgLabel;
        JProgressBar progressBar;
        final int MAXIMUM = 100;
        JPanel panel;

        progressBar = new JProgressBar(0, MAXIMUM);
        progressBar.setIndeterminate(true);
        msgLabel = new JTextArea("deneme");
        msgLabel.setEditable(false);

        panel = new JPanel(new BorderLayout(5, 5));
        panel.add(msgLabel, BorderLayout.PAGE_START);
        panel.add(progressBar, BorderLayout.CENTER);
        panel.setBorder(BorderFactory.createEmptyBorder(11, 11, 11, 11));

        final JDialog dialog = new JDialog();
        dialog.getContentPane().add(panel);
        dialog.setResizable(false);
        dialog.pack();
        dialog.setSize(500, dialog.getHeight());
        dialog.setLocationRelativeTo(null);
        dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
        dialog.setAlwaysOnTop(false);
        dialog.setVisible(true);
        msgLabel.setBackground(panel.getBackground());

        SwingWorker worker = new SwingWorker() {

            @Override
            protected void done() {
                // Close the dialog
                dialog.dispose();
            }

            @Override
            protected void process(List chunks) {
                // Here you can process the result of "doInBackGround()"
                // Set a variable in the dialog or etc.
            }

            @Override
            protected Object doInBackground() throws Exception {
                // Do the long running task here
                // Call "publish()" to pass the data to "process()"
                // return something meaningful
                return null;
            }
        };

        worker.execute();

    }
}

Edit : "publish()" should be called in "doInBackground()" to pass the data to "process()".