SwingWorker not responding

Question

What I am trying to do ?

At the click of the Start JButton, the SwingWorker will execute. Inside the doInBackground(

Answer 1

Amplifying on the other answers, don't update the GUI from your background thread, which blocks the EDT, and don't try to avoid the problem with invokeLater(). Instead, publish() the desired result and update both statusLabel and tArea in process(), as suggested below. For testing, Thread.sleep(100) simulates a small latency, but you can use Thread.yield(), as shown here. You can also update the GUI in a PropertyChangeListener, as shown here.

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.*;
import javax.swing.*;

public class SwingWorkerExample1 {

    private JLabel statusLabel;
    private JTextArea tArea;
    private JButton startButton;
    private JButton stopButton;
    private BackgroundTask backgroundTask;
    private ActionListener buttonActions = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            JButton source = (JButton) ae.getSource();
            if (source == startButton) {
                startButton.setEnabled(false);
                stopButton.setEnabled(true);
                backgroundTask = new BackgroundTask();
                backgroundTask.execute();
            } else if (source == stopButton) {
                backgroundTask.cancel(true);
                stopButton.setEnabled(false);
                startButton.setEnabled(true);
            }
        }
    };

    private void displayGUI() {
        JFrame frame = new JFrame("Swing Worker Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setBorder(
            BorderFactory.createEmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(5, 5));

        statusLabel = new JLabel("Status Bar", JLabel.CENTER);

        tArea = new JTextArea(20, 20);
        tArea.setWrapStyleWord(true);
        tArea.setLineWrap(true);
        JScrollPane textScroller = new JScrollPane();
        textScroller.setBorder(
            BorderFactory.createTitledBorder("Textual OUTPUT : "));
        textScroller.setViewportView(tArea);

        startButton = new JButton("Start");
        startButton.addActionListener(buttonActions);
        stopButton = new JButton("Stop");
        stopButton.setEnabled(false);
        stopButton.addActionListener(buttonActions);
        JPanel buttonPanel = new JPanel();
        buttonPanel.add(startButton);
        buttonPanel.add(stopButton);

        contentPane.add(statusLabel, BorderLayout.PAGE_START);
        contentPane.add(textScroller, BorderLayout.CENTER);
        contentPane.add(buttonPanel, BorderLayout.PAGE_END);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private class BackgroundTask extends SwingWorker {

        private int counter = 0;
        private String[] arrNames = {"US Rates Strategy Cash",
            "Pavan Wadhwa(1-212) 844-4597", "Srini Ramaswamy(1-212) 844-4983",
            "Meera Chandan(1-212) 855-4555", "Kimberly Harano(1-212) 823-4996",
            "Feng Deng(1-212) 855-2555", "US Rates Strategy Derivatives",
            "Srini Ramaswamy(1-212) 811-4999",
            "Alberto Iglesias(1-212) 898-5442",
            "Praveen Korapaty(1-212) 812-3444", "Feng Deng(1-212) 812-2456",
            "US Rates Strategy Derivatives", "Srini Ramaswamy(1-212) 822-4999",
            "Alberto Iglesias(1-212) 822-5098",
            "Praveen Korapaty(1-212) 812-3655", "Feng Deng(1-212) 899-2222"};

        public BackgroundTask() {
            statusLabel.setText((this.getState()).toString());
        }

        @Override
        protected Void doInBackground() {
            while (!isCancelled()) {
                counter %= arrNames.length;
                publish(arrNames[counter]);
                counter++;
                try {
                    Thread.sleep(100); // simulate latency
                } catch (InterruptedException ex) {
                    publish("Cancelled: " + isCancelled());
                }
            }
            return null;
        }

        @Override
        protected void process(java.util.List messages) {
            statusLabel.setText((this.getState()).toString());
            for (String message : messages) {
                tArea.append(String.format(message + "%n"));
            }
        }
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new SwingWorkerExample1().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}