FULL PRODUCT VERSION :
java version "1.6.0_10"
Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
Java HotSpot(TM) Client VM (build 11.0-b15, mixed mode, sharing)
ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]
A DESCRIPTION OF THE PROBLEM :
According to the API documentation for SwingWorker, 'protected void done()' is "Executed on the Event Dispatch Thread after the doInBackground method is finished."
This works as described when SwingWorker finishes normally.
But when the SwingWorker is cancelled using 'boolean cancel(boolean)' and properly handled inside doInBackground(), done() method gets executed on the EDT before doInBackground() returns.
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Please see 'Source code for an executable test case'.
EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The done() method should get executed on the EDT after doInBackground() returns.
ACTUAL -
When SwingWorker is cancelled, done() method gets executed on the EDT as soon as cancel(boolean) is called and not just after doInBackground() returns.
REPRODUCIBILITY :
This bug can be reproduced always.
---------- BEGIN SOURCE ----------
/*
* MainFrame.java
*
* Created on March 14, 2009, 8:37 AM
*/
package test;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import javax.swing.AbstractListModel;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class MainFrame extends javax.swing.JFrame {
private IntegerListModel listModel = null;
private NumberLister lister = null;
private void initialize() {
listModel = new IntegerListModel();
lstNumbers.setModel(listModel);
btnStart.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String text = txtLoopCount.getText().trim();
int loopCount;
try {
loopCount = Integer.parseInt(text);
lister = new NumberLister(loopCount);
WaiterDialog waiter = new WaiterDialog(MainFrame.this,
lister);
lister.execute();
} catch (NumberFormatException nfe) {
JOptionPane.showMessageDialog(MainFrame.this,
"An integer is required!", "Error",
JOptionPane.ERROR_MESSAGE);
}
}
});
showCount(0);
setLocationRelativeTo(null);
}
private void showCount(int count) {
lblCount.setText( String.format("Count: %d", count) );
}
private void whenStopped() {
if (lister != null) {
lister.cancel(false);
}
}
private void whenDone() {
if (lister != null) {
lister.displayResult();
}
}
private class WaiterDialog extends JDialog {
private SwingWorker worker = null;
private PropertyChangeListener workerStateListener = null;
public WaiterDialog(JFrame parent, SwingWorker worker) {
super(parent, "Please wait!", true);
JLabel lblMessage = new JLabel("Loading...");
JProgressBar prgbrStatus = new JProgressBar();
prgbrStatus.setIndeterminate(true);
JButton btnStop = new JButton("Stop");
btnStop.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
whenStopped();
}
});
Box hBox1 = new Box(BoxLayout.LINE_AXIS);
hBox1.add(lblMessage);
hBox1.add(Box.createHorizontalGlue());
Box hBox2 = new Box(BoxLayout.LINE_AXIS);
hBox2.add(prgbrStatus);
hBox2.add(Box.createHorizontalStrut(5));
hBox2.add(btnStop);
Box vBox = new Box(BoxLayout.PAGE_AXIS);
vBox.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
vBox.add(hBox1);
vBox.add(hBox2);
getContentPane().add(vBox);
pack();
setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
setResizable(false);
setLocationRelativeTo(parent);
workerStateListener = new PropertyChangeListener() {
public void propertyChange(PropertyChangeEvent e) {
Object value = e.getNewValue();
if ( value == SwingWorker.StateValue.STARTED ) {
setVisible(true);
} else if ( value == SwingWorker.StateValue.DONE ) {
whenDone();
setVisible(false);
}
}
};
worker.addPropertyChangeListener(workerStateListener);
}
}
private class NumberLister extends SwingWorker<Void, Void> {
private int loopCount;
private List<Integer> integerList = null;
public NumberLister(int loopCount) {
this.loopCount = loopCount;
}
protected Void doInBackground() throws Exception {
Random random = new Random();
integerList = new ArrayList<Integer>();
int i = 0, count = 0;
while (!isCancelled()) {
if (i >= loopCount) {
break;
}
for (int j = 0; j < 100000; j++) {
int value = random.nextInt();
if (value >= 0) {
integerList.add(value);
count++;
System.out.printf("Count = %d%n", count);
}
}
try {
Thread.sleep(200);
} catch (InterruptedException ie) {}
i++;
}
Collections.sort(integerList);
return null;
}
@Override
protected void done() {
System.out.printf("Done; IsEventDispatchThread = %s%n",
SwingUtilities.isEventDispatchThread());
}
public void displayResult() {
if (integerList != null) {
listModel.clearList();
listModel.addItems(integerList);
showCount(listModel.getSize());
}
}
}
private class IntegerListModel extends AbstractListModel {
private List<Integer> list = null;
public IntegerListModel() {
list = new ArrayList<Integer>();
}
public void clearList() {
int lastIndex = list.size() - 1;
if (lastIndex >= 0) {
list.clear();
fireIntervalRemoved(this, 0, lastIndex);
}
}
public void addItems(Collection<Integer> collection) {
if (collection.size() != 0) {
int startIndex = list.size();
list.addAll(collection);
int endIndex = list.size() - 1;
fireIntervalAdded(this, startIndex, endIndex);
}
}
public int getSize() {
return list.size();
}
public Object getElementAt(int i) {
return list.get(i);
}
}
private JButton btnStart;
private JLabel lblCount;
private JLabel lblLoopCount;
private JList lstNumbers;
private JTextField txtLoopCount;
/**
* Initialize all the components in the frame.
*/
private void initComponents() {
lstNumbers = new JList();
lstNumbers.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
lblLoopCount = new JLabel("Loop Count:");
txtLoopCount = new JTextField();
btnStart = new JButton("Start");
lblCount = new JLabel("Count");
Box vbox = new Box(BoxLayout.Y_AXIS);
Box hbox1 = new Box(BoxLayout.X_AXIS);
Box hbox2 = new Box(BoxLayout.X_AXIS);
hbox1.add(lblLoopCount);
hbox1.add(Box.createHorizontalStrut(5));
hbox1.add(txtLoopCount);
hbox1.setMaximumSize(new Dimension(Integer.MAX_VALUE,
txtLoopCount.getPreferredSize().height) );
hbox2.add(lblCount);
hbox2.add(Box.createHorizontalGlue());
hbox2.add(btnStart);
JScrollPane listScroller = new JScrollPane(lstNumbers);
listScroller.setPreferredSize(new Dimension(200, 220));
vbox.add(listScroller);
vbox.add(Box.createVerticalStrut(5));
vbox.add(hbox1);
vbox.add(Box.createVerticalStrut(5));
vbox.add(hbox2);
vbox.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
getContentPane().add(vbox);
setTitle("SwingWorker Fails");
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
pack();
}
/** Creates new form MainFrame */
public MainFrame() {
initComponents();
initialize();
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MainFrame().setVisible(true);
}
});
}
}
// -- The End --
---------- END SOURCE ----------
CUSTOMER SUBMITTED WORKAROUND :
The following is not tested yet.
Completely refrain from using 'protected void done()' and explicitly using SwingUtilities.invokeLater(Runnable) just before returning from doInBackground(), to call a method on the EDT to notify the completion of the SwingWorker.