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Swing UI freezes when trying to update from SwingWorker

I've tried to make a simple Swing example which uses SwingWorker to update the text of a Label. Whenever the SwingWorker finishes and tries to update the text, the UI will freeze. After closing the window it'll show a AWT-EventQueue-0 "Widget is disposed" exception.
I've tried to make sure it's running on the EDT etc, but I think I'm missing something very basic here. Could someone please look at my code and tell me what might be happening?
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.SWT;
public class MySwingWindow {
private Label mainText;
protected Shell shell;
/**
* Launch the application.
* #param args
*/
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
MySwingWindow window = new MySwingWindow();
window.open();
}
});
}
/**
* Open the window.
*/
public void open() {
Display display = Display.getDefault();
createContents();
shell.open();
shell.layout();
try {
SwingWorker<Boolean, Void> worker = new SwingWorker<Boolean, Void>() {
#Override
protected Boolean doInBackground() throws Exception {
for (int i = 0; i <= 2; i++) {
Thread.sleep(1000);
System.out.println("Running " + i);
}
return true;
}
#Override
protected void done() {
mainText.setText("Done");
}
};
worker.execute();
} catch (Exception e) {
e.printStackTrace();
}
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
/**
* Create contents of the window.
*/
protected void createContents() {
shell = new Shell();
shell.setSize(450, 300);
shell.setText("SWT Application");
mainText = new Label(shell, SWT.NONE);
mainText.setBounds(78, 84, 55, 15);
mainText.setText("Working");
}
}

SwingWorker doInBackground() doesn't work

I am trying to show a progress bar while I do some tasks on a database. The Progress bar, however, freezes and the Things I want to do on the database aren't executed. I understand that, in order to guarantee proper concurrency in Swing I need to do the database tasks on a secondary thread. I also understand that somehow my bug has to do with JOptionPane. But I can't come up with a solution to fix it. Here is the Code for my Progress Dialog:
public class ProgressDialog extends JDialog {
/**
*
*/
private static final long serialVersionUID = 1L;
public ProgressDialog() {
setModal(true);
setTitle("Fortschritt");
setSize(200, 100);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
JProgressBar pb = new JProgressBar();
pb.setIndeterminate(true);
pb.setValue(0);
add(pb);
setVisible(true);
}
}
And here is the Code where I call this constructor:
int result = JOptionPane.showConfirmDialog(GUIAutoTest.jtable,
"Schaden mit Testkonfig = " + index + " anlegen ?", "Bestätigen",
JOptionPane.YES_NO_OPTION);
if (result == JOptionPane.YES_OPTION) {
new SwingWorker<Void, Void>() {
final ProgressDialog pd = new ProgressDialog();
#Override
protected Void doInBackground() throws Exception {
InitTestLauf itl;
try {
itl = new InitTestLauf(index);
StartTestLauf stl = new StartTestLauf(itl.getIdTstLauf());
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
#Override
protected void done() {
System.out.println("done");
pd.setVisible(false);
}
}.execute();
JOptionPane.showMessageDialog(GUIAutoTest.jtable,
"Schaden angelegt. " + "Schadennummer: " + StartTestLauf.getSchadenNr(),
"Schaden angelegt", JOptionPane.PLAIN_MESSAGE);
It doesn't matter, what happens inside the doInBackground()-block , not even System.out.println("print something") does work. Where is my mistake ?
Thanks in advance!

I made an example that uses a progress bar with a dialog and a swingworker.
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;
import java.util.List;
/**
* Created on 13.06.17.
*/
public class DialogJunker {
static class ProgressDialog extends JDialog {
JProgressBar bar;
ProgressDialog(){
setModal(true);
bar = new JProgressBar();
add(bar);
pack();
}
void setProgress(int i){
bar.setValue(i);
}
}
public static void main(String[] args){
JFrame frame = new JFrame("diddly dialog");
JButton button = new JButton("start");
button.addActionListener(evt->{
ProgressDialog log = new ProgressDialog();
new SwingWorker<Void, Integer>(){
#Override
public Void doInBackground(){
for(int i = 0; i<100; i++){
try{
Thread.sleep(10);
publish(i);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return null;
}
#Override
public void done(){
log.setVisible(false);
log.dispose();
}
#Override
protected void process(List<Integer> ints){
log.setProgress(ints.get(0));
}
}.execute();
log.setVisible(true);
});
frame.add(button);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
This example will show a dialog with a progress bar that gets updated, then close the dialog when finished.
After reviewing you code a little more, I do see the problem. You are constructing the ProgressDialog in the SwingWorker class, but you set your progress dialog to visible, which blocks. Take note that I have solved quite a few issues.
I call set visible after starting the swing worker.
I publish the results so that the dialog actually gets updated.
I keep a reference to the progress bar, so it actually can be updated.

SWT StackLayout topControl apparently not working

I am testing a simple SWT StackLayout example to learn how it works but things are not working as I expected.
I created a StackLayout with two buttons on them, both set to cycle the top control between the two of them five times when they are selected, with a 2-second pause every time the top control changes. However, when I run the problem I do not see anything happen.
Any ideas on what I am missing?
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StackLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
public class MyApp {
protected Shell shlMyFirstSwt;
Button btnOne;
Button btnTwo;
/**
* Launch the application.
* #param args
*/
public static void main(String[] args) {
try {
MyApp window = new MyApp();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Open the window.
*/
public void open() {
Display display = Display.getDefault();
createContents();
shlMyFirstSwt.open();
shlMyFirstSwt.layout();
while (!shlMyFirstSwt.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
/**
* Create contents of the window.
* #throws InterruptedException
*/
protected void createContents() {
shlMyFirstSwt = new Shell();
shlMyFirstSwt.setSize(621, 416);
shlMyFirstSwt.setText("My First SWT Application");
StackLayout layout = new StackLayout();
shlMyFirstSwt.setLayout(layout);
Button btnOne = new Button(shlMyFirstSwt, SWT.NONE);
btnOne.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
for (int i = 0; i != 10; i++) {
layout.topControl = i % 2 == 0? btnOne : btnTwo;
shlMyFirstSwt.layout();
try {
Thread.sleep(2000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
});
btnOne.setText("One");
Button btnTwo = new Button(shlMyFirstSwt, SWT.NONE);
btnTwo.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
for (int i = 0; i != 10; i++) {
layout.topControl = i % 2 == 0? btnOne : btnTwo;
shlMyFirstSwt.layout();
try {
Thread.sleep(2000);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
});
btnTwo.setText("Two");
}
}
Elaborating after first answer:
Trying a simpler approach without delaying. Now I modified the event handler to simply have one button switch the top control to be the other button, as shown below. I expected the two buttons to alternate as top control, but instead when I click on the first button, the window turns blank. Any idea why?
Button btnOne = new Button(shlMyFirstSwt, SWT.NONE);
btnOne.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
layout.topControl = btnTwo;
shlMyFirstSwt.layout();
}
});
btnOne.setText("One");
Button btnTwo = new Button(shlMyFirstSwt, SWT.NONE);
btnTwo.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
layout.topControl = btnOne;
shlMyFirstSwt.layout();
}
});
btnTwo.setText("Two");

Your Thread.sleep calls are blocking the user interface thread so the GUI does not get updated. You must never block the user interface thread like this. Calls to methods like layout do not update instantly - they require that display.readAndDispatch runs to dispatch the various updates that are generated.
If you want to delay something use Display.timerExec:
Display.getDefault().timerExec(2000, new Runnable() {
#Override
public void run()
{
... code to be run after the delay
}
});
So you will have to rework your code to use this to do the timed updated.

Figured it out: just the silly mistake of including btnTwo in the first event handler before it was initialized, even though it is used after initialization.

SWT application showing updated display in near realtime

Question:
Can you show any simple example or explanation of SWT display part(which updates the window/shell)? Or can you any sites that you think they are the best for SWT application development?
Background:
I am new to SWT application and currently building an application for running some tests.
It has a main display shell class with text area which keeps getting updated after user clicked on a run button.
The run button starts another thread process which updates public static object such as AtomicCounter in the StartView class.
Current Stage
The program seems running well, however, it does not update the text area in realtime.
Well, I can't say realtime but it shows a little bit delayed information.(I can say it's delayed because I print out on the console as well)
It seems like I don't understand displaying concept of SWT well enough to do whatever I am trying to do with it.
Goal
A. Main Display class which starts and stops C regardless of B running or not
B. Threaded process which updates text area of A class with public static object of A
C. Threaded process which does its job and updating public static object of A
Example Code (Working Code)
public class UnitTest {
public static Display display;
private Shell shell;
public static AtomicInteger counter = new AtomicInteger(0);
public static Text text;
private TestThread test1 = null, test2 = null;
public UnitTest()
{
display = Display.getDefault();
this.shell = new Shell(display, SWT.CLOSE);
this.shell.setSize(226, 120);
text = new Text(shell, SWT.BORDER);
text.setBounds(10, 10, 199, 19);
Button btnStart = new Button(shell, SWT.NONE);
btnStart.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent arg0) {
test1 = new TestThread();
test1.start();
test2 = new TestThread();
test2.start();
}
});
btnStart.setBounds(10, 54, 94, 28);
btnStart.setText("Start");
Button btnStop = new Button(shell, SWT.NONE);
btnStop.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent arg0) {
test1.interrupt();
test2.interrupt();
counter.set(0);
}
});
btnStop.setBounds(115, 54, 94, 28);
btnStop.setText("Stop");
this.shell.open();
this.shell.layout();
this.shell.addListener(SWT.Close, new Listener(){
public void handleEvent(Event event)
{
shell.dispose();
}
});
while(!this.shell.isDisposed())
{
if(!display.readAndDispatch())
{
//text.setText(""+counter.get());
display.sleep();
}
}
}
public static void main(String[] args)
{
new UnitTest();
}
}
class TestThread extends Thread
{
public void run()
{
try
{
int i = 0;
while(i++ < 1000 && !this.isInterrupted() )
{
UnitTest.counter.getAndIncrement();
try {
TestThread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
break;
}
if(UnitTest.display.isDisposed())
return;
UnitTest.display.asyncExec(new Runnable() {
public void run() {
if (UnitTest.text.isDisposed())
return;
UnitTest.text.setText(""+UnitTest.counter.get());
}
});
}
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
System.out.println("Existing thread...");
}
}
}

You should carefully use UI updates from separate threads. Please, read this:
http://goo.gl/At8hC

SWT - Inheriting parent dialog shell?

I am really needing to understand how parent/child dialogs work.
My users use a OTB Application called Teamcenter. I am writing a add on application that is invoked from a menu selection in the Teamcenter Application.
When they click the menu item, that executes a handler class and that creates the base dialog for my application.
public class AplotDialogHandler extends AbstractHandler {
private static AplotBaseDialog dlg = null;
public AplotDialogHandler() {
}// end Constructor
//////////////////////////////////////////////////////////////////////////
// execute() //
//////////////////////////////////////////////////////////////////////////
#Override
public Object execute(final ExecutionEvent event) throws ExecutionException {
if (dlg == null) {
try {
AbstractAIFApplication app = AIFDesktop.getActiveDesktop().getCurrentApplication();
TCSession session = (TCSession) app.getSession();
TCUserService userService = session.getUserService();
AplotVersion.negotiateVersion(userService);
AplotQueryCapabilities.initialize(userService);
dlg = new AplotBaseDialog(null, session);
}
catch (Exception ex) {
MessageBox.post(HandlerUtil.getActiveWorkbenchWindowChecked(event).getShell(), ex, true);
}
}
dlg.create();
dlg.getShell().setSize(700, 400);
dlg.open();
return null;
}// end execute()
}// end EdiDialogHandler()
Question 1. It seems like my application is not tied to the Teamcenter application. Meaning that I can close Teamcenter and my Application stays open.
Question 2. Should I get the workspace shell and pass it in the base dialog?
But even when my application is open, the user still needs to be able to use the Teamcenter application to select data to send to my application
Question 3. When opening dialogs from my base dialog, should I always pass the base dialog shell to those dialogs?
Question 4. Is there a standard way I should close down the dialogs when the user is done?

You need to pass the parent Shell to the dialog so that when you close parent shell, child shells will also be closed.
You should make your dialog MODELESS ( use SWT.MODELSS as style. Note: it is Hint) so that it will not block your parent shell.
Here is sample code:
public static void main(String[] args) {
Display display = new Display();
final Shell shell = new Shell(display);
shell.setLayout(new GridLayout(1, false));
shell.setSize(200, 200);
Button b = new Button(shell, SWT.NONE);
b.setText("Click");
b.addSelectionListener(new SelectionListener() {
#Override
public void widgetSelected(SelectionEvent e) {
CDialog dialog = new CDialog(shell);
dialog.open();
}
#Override
public void widgetDefaultSelected(SelectionEvent e) {
// TODO Auto-generated method stub
}
});
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch())
display.sleep();
}
display.dispose();
}
private static class CDialog extends Dialog
{
/**
* #param parentShell
*/
protected CDialog(Shell parentShell) {
super(parentShell);
}
/* (non-Javadoc)
* #see org.eclipse.jface.dialogs.Dialog#createDialogArea(org.eclipse.swt.widgets.Composite)
*/
#Override
protected Control createDialogArea(Composite parent) {
Composite comp = (Composite) super.createDialogArea(parent);
Label lbl = new Label(comp, SWT.NONE);
lbl.setText("Test modeless dialog");
return comp;
}
/* (non-Javadoc)
* #see org.eclipse.jface.window.Window#getShellStyle()
*/
#Override
protected int getShellStyle() {
return SWT.DIALOG_TRIM|SWT.MODELESS;
}
}