Designing Graphical Interfaces - Beginning Java Programming: The Object-Oriented Approach - page 523

private SwingWorker<Boolean, Integer> backgroundTask = null;
public ProgressTrackingFrame() {
super();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Progress Tracker");
setLayout(new FlowLayout());
btn.addActionListener(this);
add(bar);
add(btn);
pack();
setVisible(true);
}
public SwingWorker<Boolean, Integer> makeBackgroundTask(final long total) {
SwingWorker<Boolean, Integer> task = new SwingWorker<Boolean, Integer>(){
@Override
protected Boolean doInBackground() throws Exception {
btn.setText("Stop Calculation");
for (long i = 0; i < total; i++) {
if (isCancelled()) {
bar.setValue(0);
return false;
}
int perc = (int)
(i * (bar.getMaximum() - bar.getMinimum())
/ total);
publish(perc);
}
return true;
}
@Override
protected void process(List<Integer> percs) {
for (int perc : percs)
if (bar.getValue() < perc)
bar.setValue(perc);
}
@Override
public void done() {
btn.setText("Start Calculation");
backgroundTask = null;
}
};
return task;
}
@Override
public void actionPerformed(ActionEvent arg0) {
if (backgroundTask == null) {
backgroundTask = makeBackgroundTask(1000000000);
backgroundTask.execute();
} else {
backgroundTask.cancel(true);
}