Currently I have two SwingWorker threads doing job on background. If an exception occurs, the method stop to work, but the thread still runnig.
How I do to stop the execution and kill the thread of the doInBackground() if an exception occurs?
this.cancel(true) don't destroy/close the thread. How can I achieve this?
@Override
protected Boolean doInBackground() throws Exception {
try {
while (true) {
//some code here
return true;
}
} catch (Exception e) {
this.cancel(true); //<-- this not cancel the thread
return false;
}
}
I see these threads in the debug of Netbeans.
'AWT-EventQueue-0' em execução
'AWT-Windows' em execução
'SwingWorker-pool-1-thread-1' em execução
'SwingWorker-pool-1-thread-2' em execução
//*em execução = in execution
jfpoilpret
By default, SwingWorker reuses worker threads, so it is perfectly normal that, even though, doInBackground() has returned, to still see the thread that executed your method.
You can identify this fact by looking at the thread names, as reported by NetBeans: SwingWorker-pool-1-thread-1, where that pool is managed by SwingWorker.
If you want more control, you can also pass the SwingWorker instance to an Executor.
Just check SwingWorker and Executor javadoc for further information.
Besides, SwingWorker.cancel() is not supposed to be called from doInBackground() but rather from another thread, generally the EDT, e.g. when user clicks a Cancel button in a progress dialog.
as jzd montioned, there is method cancel(boolean mayInterruptIfRunning); for exapmle
EDIT: with cancel(true); you have to (always) cautgh an exception java.util.concurrent.CancellationException
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
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 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
} 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();
}
});
}
}
There is a cancel() method. Your code would have to pay attention to that. If it keeps running after an exception, it would appear that you code is ignoring an exception that it shouldn't be.
FYI for anyone passing through: when a SwingWorker is canceled, done() is called before doInBackground() returns.
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6826514
Jeff
You need to add Thread.sleep(1) calls in your doInBackground() code every so often. In your sleep catch blocks, add return. I had the same problem, and this worked like a charm.
Source: https://blogs.oracle.com/swinger/entry/swingworker_stop_that_train
Till The SwingWoker it fixed http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6826514 Here a simple (tested) version with the basic (similar) functions then SwingWoker
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package tools;
import java.util.LinkedList;
import java.util.List;
import javax.swing.SwingUtilities;
/**
*
* @author patrick
*/
public abstract class MySwingWorker<R,P> {
protected abstract R doInBackground() throws Exception;
protected abstract void done(R rvalue, Exception ex, boolean canceled);
protected void process(List<P> chunks){}
protected void progress(int progress){}
private boolean cancelled=false;
private boolean done=false;
private boolean started=false;
final private Object syncprogress=new Object();
boolean progressstate=false;
private int progress=0;
final private Object syncprocess=new Object();
boolean processstate=false;
private LinkedList<P> chunkes= new LinkedList<>();
private Thread t= new Thread(new Runnable() {
@Override
public void run() {
Exception exception=null;
R rvalue=null;
try {
rvalue=doInBackground();
} catch (Exception ex) {
exception=ex;
}
//Done:
synchronized(MySwingWorker.this)
{
done=true;
final Exception cexception=exception;
final R crvalue=rvalue;
final boolean ccancelled=cancelled;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
done(crvalue, cexception, ccancelled);
}
});
}
}
});
protected final void publish(P p)
{
if(!Thread.currentThread().equals(t))
throw new UnsupportedOperationException("Must be called from worker Thread!");
synchronized(syncprocess)
{
chunkes.add(p);
if(!processstate)
{
processstate=true;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
List<P> list;
synchronized(syncprocess)
{
MySwingWorker.this.processstate=false;
list=MySwingWorker.this.chunkes;
MySwingWorker.this.chunkes= new LinkedList<>();
}
process(list);
}
});
}
}
}
protected final void setProgress(int progress)
{
if(!Thread.currentThread().equals(t))
throw new UnsupportedOperationException("Must be called from worker Thread!");
synchronized(syncprogress)
{
this.progress=progress;
if(!progressstate)
{
progressstate=true;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
int value;
//Acess Value
synchronized(syncprogress)
{
MySwingWorker.this.progressstate=false;
value=MySwingWorker.this.progress;
}
progress(value);
}
});
}
}
}
public final synchronized void execute()
{
if(!started)
{
started=true;
t.start();
}
}
public final synchronized boolean isRunning()
{
return started && !done;
}
public final synchronized boolean isDone()
{
return done;
}
public final synchronized boolean isCancelled()
{
return cancelled;
}
public final synchronized void cancel()
{
if(started && !cancelled && !done)
{
cancelled=true;
if(!Thread.currentThread().equals(t))
t.interrupt();
}
}
}
来源：https://stackoverflow.com/questions/6113944/how-cancel-the-execution-of-a-swingworker