SwingWorkerExample.java Source code

Introduction

Here is the source code for SwingWorkerExample.java

Source

import javax.swing.*;
import java.awt.event.ActionEvent;

public class SwingWorkerExample extends JPanel {
    private JLabel statusArea;
    private DefaultListModel listModel;

    public SwingWorkerExample() {
        JButton button = new JButton(new LongRunningModelFillAction());
        add(button);

        JList list = new JList();
        this.listModel = new DefaultListModel();
        this.listModel.addElement("An Empty List Model");
        list.setModel(listModel);
        add(new JScrollPane(list));

        add(new JLabel("Status:"));
        this.statusArea = new JLabel();
        add(this.statusArea);
    }

    private class LongRunningModelFillAction extends AbstractAction {
        public LongRunningModelFillAction() {
            super("Fill Model");
        }

        public void actionPerformed(ActionEvent e) {
            PopulationWorker populationWorker = new PopulationWorker();
            populationWorker.start();
        }
    }

    private class PopulationWorker extends SwingWorker {
        public Object construct() {
            Object[] values = new Object[100];
            for (int i = 1; i <= 100; i++) {
                values[i - 1] = "Value" + i;

                if ((i % 10) == 0) {
                    final int progress = i;
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            SwingWorkerExample.this.statusArea.setText("Calculated " + progress);
                        }
                    });
                }
                try {
                    Thread.sleep(50);
                } catch (InterruptedException e) {
                }
            }
            return values;
        }

        public void start() {
            SwingWorkerExample.this.listModel.removeAllElements();
            SwingWorkerExample.this.listModel.addElement("Calculating...");
            super.start();
        }

        public void finished() {
            SwingWorkerExample.this.statusArea.setText("");
            SwingWorkerExample.this.listModel.removeAllElements();
            Object[] values = (Object[]) getValue();
            for (int i = 0; i < values.length; i++) {
                SwingWorkerExample.this.listModel.addElement(values[i]);
            }
        }
    }

    public static void main(String[] a) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(1);
        f.add(new SwingWorkerExample());
        f.pack();
        f.setVisible(true);
    }

}

/*
 * $Id: SwingWorker.java,v 1.1.1.1 2004/06/16 01:43:39 davidson1 Exp $
 *
 * Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 */

/**
 * 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.
 */
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();
        }
    }
}