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Multiple threads in Java while using WindowBuilder SWT

Can someone explain me why Window in this program freezes while I try to run 2 or more threads ?
I want to be able to click on Hello button while both of threads are running.
Here is my simple project.
Task class only prints out word "Testing".
public class Task extends Thread {
public static boolean keepRun = true;
public void run(){
while(keepRun == true){
System.out.println("Testing...");
try {
Thread.sleep(1000);
}catch(InterruptedException e){}};
}
}
Closing class stops thread when it is typed stop inside console.
import java.util.Scanner;
public class Closing implements Runnable{
Scanner s = new Scanner(System.in);
public void run() {
while (s.next().equals("stop")){
System.out.println("Threads down");
Task.keepRun =false;
try {
Thread.sleep(5000);
}catch(InterruptedException e){}
};
}
}
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
Here is Window class where main is also located.
public class Window {
protected Shell shell;
/**
* Launch the application.
* #param args
*/
public static void main(String[] args) {
try {
Window window = new Window();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Open the window.
*/
public void open() {
Display display = Display.getDefault();
createContents();
shell.open();
shell.layout();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
/**
* Create contents of the window.
*/
protected void createContents() {
shell = new Shell();
shell.setSize(192, 208);
shell.setText("SWT Application");
Button btnRun = new Button(shell, SWT.NONE);
btnRun.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
Task newTask = new Task();
Closing closing = new Closing();
newTask.start();
closing.run();
}
});
btnRun.setBounds(50, 32, 75, 25);
btnRun.setText("Run");
Button btnHello = new Button(shell, SWT.NONE);
btnHello.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
System.out.println("Hello");
}
});
btnHello.setBounds(50, 81, 75, 25);
btnHello.setText("Hello");
}
}

Rewrite this:
Closing closing = new Closing();
newTask.start();
closing.run();
to this:
Closing closing = new Closing();
newTask.start();
new Thread(closing).start();
Look at this code:
public class Closing implements Runnable{
Scanner s = new Scanner(System.in);
public void run() {
while (s.next().equals("stop")){
System.out.println("Threads down");
Task.keepRun =false;
try {
Thread.sleep(5000);
}catch(InterruptedException e){}
};
}
}
If you call simply run();, Thread.sleep(5000); will be affected to thread which called run, in the other hand, when you create a new Thread, sleep will be affected to this one.

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.

Overriding Cut/Copy/Paste in SWT Text control

What is the correct way to override the cut(), copy(), and paste() methods of the Text control? What triggers the execution of these methods?
I have created an example application with a custom class that overrides these methods. Unfortunately, nothing seems to execute these overridden methods, including the act of using Ctrl+X / Ctrl+C / Ctrl+V or selecting cut/copy/paste from the context menu.
Custom Text Class:
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Text;
public class TextCopyable extends Text{
public TextCopyable(Composite parent, int style) {
super(parent, style);
}
#Override
public void checkSubclass() {
}
#Override
public void cut() {
System.out.println("Cut!");
}
#Override
public void copy() {
System.out.println("Copy!");
}
#Override
public void paste() {
System.out.println("Paste!");
}
}
Test Shell:
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.layout.GridData;
public class CopyPasteTest extends Shell {
private TextCopyable text;
public static void main(String args[]) {
try {
Display display = Display.getDefault();
CopyPasteTest shell = new CopyPasteTest(display);
shell.open();
shell.layout();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
public CopyPasteTest(Display display) {
super(display, SWT.SHELL_TRIM);
createContents();
}
protected void createContents() {
setText("SWT Application");
setSize(450, 300);
GridLayout gridLayout = new GridLayout();
setLayout(gridLayout);
text = new TextCopyable(this, SWT.BORDER);
text.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1));
}
#Override
protected void checkSubclass() {
// Disable the check that prevents subclassing of SWT components
}
}
My expectation was that the copy() method would be called any time that I use the Ctrl+C command to copy text from the textbox. However, the methods do not trigger at all. Is my assumption faulty?

Java SwingWorker with JDialog showing JProgressBar during JDBC network operation

I have a frame which has a button, when it is pressed a JDialog with a progress bar is shown and some data is being fetched using jdbc driver (progress bar is being updated). I needed a cancel button, so I spent some time figuring out how to connect everything. It seems to be working, but I sincerely am not sure if this way is any good. If someone has some spare time please check this code and tell me if anything is wrong with it - mainly with the whole SwingWorker and cancellation stuff.
On my pc (linux) the unsuccessful network connection attempt (someNetworkDataFetching method) takes a whole minute to timeout, do I have to worry about the SwingWorkers which are still working (waiting to connect despite being cancelled) when I try to create new ones?
Note: you need mysql jdbc driver library to run this code.
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class Test extends JFrame {
private JProgressBar progressBar = new JProgressBar();
private JLabel label = new JLabel();
private DataFetcherProgress dfp;
/**
* This class holds retrieved data.
*/
class ImportantData {
ArrayList<String> chunks = new ArrayList<>();
void addChunk(String chunk) {
// Add this data
chunks.add(chunk);
}
}
/**
* This is the JDialog which shows data retrieval progress.
*/
class DataFetcherProgress extends JDialog {
JButton cancelButton = new JButton("Cancel");
DataFetcher df;
/**
* Sets up data fetcher dialog.
*/
public DataFetcherProgress(Test owner) {
super(owner, true);
getContentPane().add(progressBar, BorderLayout.CENTER);
// This button cancels the data fetching worker.
cancelButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
df.cancel(true);
}
});
getContentPane().add(cancelButton, BorderLayout.EAST);
setLocationRelativeTo(owner);
setSize(200, 50);
df = new DataFetcher(this);
}
/**
* This executes data fetching worker.
*/
public void fetchData() {
df.execute();
}
}
class DataFetcher extends SwingWorker<ImportantData, Integer> {
DataFetcherProgress progressDialog;
public DataFetcher(DataFetcherProgress progressDialog) {
this.progressDialog = progressDialog;
}
/**
* Update the progress bar.
*/
#Override
protected void process(List<Integer> chunks) {
if (chunks.size() > 0) {
int step = chunks.get(chunks.size() - 1);
progressBar.setValue(step);
}
}
/**
* Called when worker finishes (or is cancelled).
*/
#Override
protected void done() {
System.out.println("done()");
ImportantData data = null;
try {
data = get();
} catch (InterruptedException | ExecutionException | CancellationException ex) {
System.err.println("done() exception: " + ex);
}
label.setText(data != null ? "Retrieved data!" : "Did not retrieve data.");
progressDialog.setVisible(false);
}
/**
* This pretends to do some data fetching.
*/
private String someNetworkDataFetching() throws SQLException {
DriverManager.getConnection("jdbc:mysql://1.1.1.1/db", "user", "pass");
// Retrieve data...
return "data chunk";
}
/**
* This tries to create ImportantData object.
*/
#Override
protected ImportantData doInBackground() throws Exception {
// Show the progress bar dialog.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
dfp.setVisible(true);
}
});
ImportantData data = new ImportantData();
try {
int i = 0;
// There is a network operation here (JDBC data retrieval)
String chunk1 = someNetworkDataFetching();
if (isCancelled()) {
System.out.println("DataFetcher cancelled.");
return null;
}
data.addChunk(chunk1);
publish(++i);
// And another jdbc data operation....
String chunk2 = someNetworkDataFetching();
if (isCancelled()) {
System.out.println("DataFetcher cancelled.");
return null;
}
data.addChunk(chunk2);
publish(++i);
} catch (Exception ex) {
System.err.println("doInBackground() exception: " + ex);
return null;
}
System.out.println("doInBackground() finished");
return data;
}
}
/**
* Set up the main window.
*/
public Test() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
label.setHorizontalAlignment(SwingConstants.CENTER);
getContentPane().add(label, BorderLayout.CENTER);
// Add a button starting data fetch.
JButton retrieveButton = new JButton("Do it!");
retrieveButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
fetchData();
}
});
getContentPane().add(retrieveButton, BorderLayout.EAST);
setSize(400, 75);
setLocationRelativeTo(null);
progressBar.setMaximum(2);
}
// Shows new JDialog with a JProgressBar and calls its fetchData()
public void fetchData() {
label.setText("Retrieving data...");
dfp = new DataFetcherProgress(this);
dfp.fetchData();
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
// Use jdbc mysql driver
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
return;
}
// Show the Frame
new Test().setVisible(true);
}
});
}
}

About the only thing I might do different is not use the SwingUtilities.invokeLater in the doInBackground method to show the dialog, but maybe use a PropertyChangeListener to monitor the changes to the state property worker.
I would also use the PropertyChangeListener to monitor the changes to the progress property of the worker. Instead of using publish to indicate the progression changes I would use the setProgress method (and getProgress in the PropertyChangeListener)
For example...java swingworker thread to update main Gui
I might also consider creating the UI on a JPanel and adding it to the JDialog rather then extending directory from JDialog as it would give the oppurtunity to re-use the panel in other ways, should you wish...

an indeterminate progressbar in new window in swt

I am designing interface of java application using window builder. What I need to do is..
Click on a button does two things 1. do some background task
2. while this is in progress, display an indeterminate progressbar n new window.
I know I need multithreading to accomplish this.
I tried taking the help of some tutorials but could not implement this.
Can anyone help?
code:
Function from where I want to open the progress bar window
public void mouseDown(MouseEvent e) {
pbar p=new pbar();
p.caller();
dowork();
p.closeprogress();
}
Progressbar class
import org.eclipse.swt.widgets.Display;
public class pbar {
protected Shell shell;
public void pcaller() {
try {
//System.err.println("Error: " + bod);
//System.err.println("Error: " + lines);
pbar window = new pbar();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Open the window.
*/
public void open() {
Display display = Display.getDefault();
createContents();
shell.open();
shell.layout();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
/**
* Create contents of the window.
*/
protected void createContents() {
shell = new Shell();
shell.setSize(315, 131);
shell.setText("Updating!!! Please Wait");
ProgressBar progressBar = new ProgressBar(shell, SWT.INDETERMINATE);
progressBar.setBounds(47, 34, 195, 17);
// ProgressBar pb2 = new ProgressBar(shell, SWT.HORIZONTAL |
SWT.INDETERMINATE);
// pb2.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
}
public void close()
{
shell.close();
}
}
I want when I call p.caller(), progress bar will appear. Then, control should come to original program and execute dowork() method. when i am done with this method, it will call p.progress.close().
I Don't know why isn't understanding this simple program, forget about answering.

Is use of JFace acceptable?
If so you can use ProgressMonitorDialog class.
ProgressMonitorDialog dialog = new ProgressMonitorDialog(parent.getShell());
dialog.run(true, true, new SomeTask());
...
class SomeTask implements IRunnableWithProgress {
#Override
public void run(IProgressMonitor monitor) throws InvocationTargetException,
InterruptedException {
monitor.beginTask("Doing some task", IProgressMonitor.UNKNOWN);
for(int i = 0; i < 1000; i++) {
if (!monitor.isCanceled())
Thread.sleep(10);
}
monitor.done();
}
}
You can find complete example of usage here.

Try using.....
JProgressBar p = new JProgressBar();
p.setStringPainted();
Now where the value needs to be set.
p.setValue(val);
To display a message when done.
p.setString("done");