I have a ProgressMonitor pm and a SwingWorker sw. I want to cancel the SwingWorker when I press the cancel-button on pm. I guess this shouldnt be too hard, and I read some tutorials about SwingWorker and ProgressMonitor, but I can't get this to work.
final ProgressMonitor pm = new ProgressMonitor(frame, "checking", "...", 0, 100);
final SwingWorker sw = new SwingWorker()
{
protected Object doInBackground() throws Exception
{
doSomethingAndUpdateProgress();
}
};
sw.addPropertyChangeListener(new PropertyChangeListener()
{
public void propertyChange(PropertyChangeEvent evt)
{
if(evt.getPropertyName().equals("progress"))
{
updateProgress();
}
if(pm.isCanceled())
{
cancelAction();
}
if(pm.isDone())
{
doneAction();
}
}
});
sw.execute();
Progress updating is working just fine, but pm.isCanceled() is never true. I suppose I need a propertyChangeListener for the ProgressMonitor, but I dont know how I would add one there.
During the execution of your long running task, you want to periodically check if the ProgressMonitor was canceled. It's your job to check that at points where it makes sense to cancel the task - otherwise who knows what resources you could leave hanging.
So basically, you want to change your doSomethingAndUpdateProgress() method so that it also checks if the ProgressMonitor was canceled.
Here's a demo that shows how this works:
import java.awt.*;
import javax.swing.*;
public class TempProject extends Box{
public TempProject(){
super(BoxLayout.Y_AXIS);
final ProgressMonitor pm = new ProgressMonitor(this, "checking", "...", 0, 100);
final SwingWorker sw = new SwingWorker<Integer, Integer>()
{
protected Integer doInBackground() throws Exception
{
int i = 0;
//While still doing work and progress monitor wasn't canceled
while (i++ < 100 && !pm.isCanceled()) {
System.out.println(i);
publish(i);
Thread.sleep(100);
}
return null;
}
@Override
protected void process(java.util.List<Integer> chunks) {
for (int number : chunks) {
pm.setProgress(number);
}
}
};
sw.execute();
}
public static void main(String args[])
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setContentPane(new TempProject());
frame.pack();
frame.setVisible(true);
}
});
}
}
and I read some tutorials about SwingWorker and ProgressMonitor, but I can't get this to work.
canceling always invoked an InteruptedExeption,
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
public class SwingWorkerExample extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
private final JButton startButton, stopButton;
private JScrollPane scrollPane = new JScrollPane();
private JList listBox = null;
private DefaultListModel listModel = new DefaultListModel();
private final JProgressBar progressBar;
private mySwingWorker swingWorker;
public SwingWorkerExample() {
super("SwingWorkerExample");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setLayout(new GridLayout(2, 2));
startButton = makeButton("Start");
stopButton = makeButton("Stop");
stopButton.setEnabled(false);
progressBar = makeProgressBar(0, 99);
listBox = new JList(listModel);
scrollPane.setViewportView(listBox);
getContentPane().add(scrollPane);
//Display the window.
pack();
setVisible(true);
}
//Class SwingWorker<T,V> T - the result type returned by this SwingWorker's doInBackground
//and get methods V - the type used for carrying out intermediate results by this SwingWorker's
//publish and process methods
private class mySwingWorker extends javax.swing.SwingWorker<ArrayList<Integer>, Integer> {
//The first template argument, in this case, ArrayList<Integer>, is what s returned by doInBackground(),
//and by get(). The second template argument, in this case, Integer, is what is published with the
//publish method. It is also the data type which is stored by the java.util.List that is the parameter
//for the process method, which recieves the information published by the publish method.
@Override
protected ArrayList<Integer> doInBackground() {
//Returns items of the type given as the first template argument to the SwingWorker class.
if (javax.swing.SwingUtilities.isEventDispatchThread()) {
System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() returned true.");
}
Integer tmpValue = new Integer(1);
ArrayList<Integer> list = new ArrayList<Integer>();
for (int i = 0; i < 100; i++) {
for (int j = 0; j < 100; j++) { //find every 100th prime, just to make it slower
tmpValue = FindNextPrime(tmpValue.intValue());
//isCancelled() returns true if the cancel() method is invoked on this class. That is the proper way
//to stop this thread. See the actionPerformed method.
if (isCancelled()) {
System.out.println("SwingWorker - isCancelled");
return list;
}
}
//Successive calls to publish are coalesced into a java.util.List, which is what is received by process,
//which in this case, isused to update the JProgressBar. Thus, the values passed to publish range from
//1 to 100.
publish(new Integer(i));
list.add(tmpValue);
}
return list;
}//Note, always use java.util.List here, or it will use the wrong list.
@Override
protected void process(java.util.List<Integer> progressList) {
//This method is processing a java.util.List of items given as successive arguments to the publish method.
//Note that these calls are coalesced into a java.util.List. This list holds items of the type given as the
//second template parameter type to SwingWorker. Note that the get method below has nothing to do with the
//SwingWorker get method; it is the List's get method. This would be a good place to update a progress bar.
if (!javax.swing.SwingUtilities.isEventDispatchThread()) {
System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() + returned false.");
}
Integer percentComplete = progressList.get(progressList.size() - 1);
progressBar.setValue(percentComplete.intValue());
}
@Override
protected void done() {
System.out.println("doInBackground is complete");
if (!javax.swing.SwingUtilities.isEventDispatchThread()) {
System.out.println("javax.swing.SwingUtilities.isEventDispatchThread() + returned false.");
}
try {
//Here, the SwingWorker's get method returns an item of the same type as specified as the first type parameter
//given to the SwingWorker class.
ArrayList<Integer> results = get();
for (Integer i : results) {
listModel.addElement(i.toString());
}
} catch (Exception e) {
System.out.println("Caught an exception: " + e);
}
startButton();
}
boolean IsPrime(int num) { //Checks whether a number is prime
int i;
for (i = 2; i <= num / 2; i++) {
if (num % i == 0) {
return false;
}
}
return true;
}
protected Integer FindNextPrime(int num) { //Returns next prime number from passed arg.
do {
if (num % 2 == 0) {
num++;
} else {
num += 2;
}
} while (!IsPrime(num));
return new Integer(num);
}
}
private class TaskListener implements PropertyChangeListener {
private String name;
TaskListener(String name) {
this.name = name;
}
@Override
public void propertyChange(PropertyChangeEvent e) {
System.out.println(name + ": "
+ e.getOldValue() + " -> " + e.getNewValue());
}
}
private JButton makeButton(String caption) {
JButton b = new JButton(caption);
b.setActionCommand(caption);
b.addActionListener(this);
getContentPane().add(b);
return b;
}
private JProgressBar makeProgressBar(int min, int max) {
JProgressBar progressBar1 = new JProgressBar();
progressBar1.setMinimum(min);
progressBar1.setMaximum(max);
progressBar1.setStringPainted(true);
progressBar1.setBorderPainted(true);
getContentPane().add(progressBar1);
return progressBar1;
}
private void startButton() {
startButton.setEnabled(true);
stopButton.setEnabled(false);
System.out.println("SwingWorker - Done");
}
@Override
public void actionPerformed(ActionEvent e) {
if ("Start" == null ? e.getActionCommand() == null : "Start".equals(e.getActionCommand())) {
startButton.setEnabled(false);
stopButton.setEnabled(true);
// Note that it creates a new instance of the SwingWorker-derived class. Never reuse an old one.
(swingWorker = new mySwingWorker()).execute(); // new instance
swingWorker.addPropertyChangeListener(new TaskListener("Task"));
} else if ("Stop" == null ? e.getActionCommand() == null : "Stop".equals(e.getActionCommand())) {
startButton.setEnabled(true);
stopButton.setEnabled(false);
swingWorker.cancel(true); // causes isCancelled to return true in doInBackground
swingWorker = null;
}
}
public static void main(String[] args) {
// Notice that it kicks it off on the event-dispatching thread, not the main thread.
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
SwingWorkerExample swingWorkerExample = new SwingWorkerExample();
}
});
}
}
来源：https://stackoverflow.com/questions/12108127/getting-the-cancel-event-of-java-progressmonitor