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How do I make a loop start and end with a key press and release?

Here is my code... How can I make it work so that it runs the loop while the user is holding a button and stops when the user releases the button?
public void nextPrimeNum()
{
x = false;
int b = 2;
ArrayList<Integer> next = new ArrayList<Integer>();
while(x)
{
next = factors(b);
if(next.size()==2)
{
System.out.println(b);
}
b++;
}
System.out.println("End");
}
public void keyPressed(KeyEvent e)
{
if(e.getKeyCode() == 401)
{
x = true;
}
}
public void keyRealesed(KeyEvent e)
{
if(e.getKeyCode() == 402)
{
x = false;
}
}

GUI and multi-thread programming is inherently difficult.
So, this is as simple as it could be, without violating best practices too much.
You need several things:
A separate Thread for printing primes:
Its run method loops for ever, but pauses when the Space key is not pressed.
(see Defining and Starting a Thread for more info)
A KeyListener which will be called from AWT's event dispatch thread:
The event handling methods are designed to finish fast, so that other events
(like moving, resizing and closing the frame) still are handled fast.
(see How to Write a Key Listener
and The Event Dispatch Thread for more info)
A visible GUI component (JFrame) for adding the KeyListener
Some synchronization between the 2 threads (via synchronized, notify and wait)
so that the prime-printing starts/continues on keyPressed
and suspends on keyReleased
(see Guarded Blocks for more info)
Initialize and start the whole GUI by invoking initGUI.
(see Initial Threads for more info)
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
public class Main implements Runnable, KeyListener {
public static void main(String[] args) {
SwingUtilities.invokeLater(Main::initGUI);
}
private static void initGUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JLabel("Press SPACE key for printing primes"));
frame.pack();
frame.setLocationRelativeTo(null); // center on screen
frame.setVisible(true);
Main main = new Main();
frame.addKeyListener(main);
Thread thread = new Thread(main);
thread.start();
}
private boolean spaceKeyPressed;
private boolean isPrime(int n) {
for (int i = 2; i < n; i++) {
if (n % i == 0)
return false;
}
return true;
}
#Override
public void run() {
for (int n = 2; /**/; n++) {
while (!spaceKeyPressed) {
synchronized (this) {
try {
wait(); // waits until notify()
} catch (InterruptedException e) {
// do nothing
}
}
}
if (isPrime(n)) {
System.out.println(n);
}
}
}
#Override
public void keyTyped(KeyEvent e) {
// do nothing
}
#Override
public synchronized void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_SPACE) {
spaceKeyPressed = true;
notifyAll(); // cause wait() to finish
}
}
#Override
public synchronized void keyReleased(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_SPACE) {
spaceKeyPressed = false;
notifyAll(); // cause wait() to finish
}
}
}

So, the answer is - it's complicated. It covers broad topics such as concurrency (in general), GUI development, best practices with the specific API (Swing) which are better covered in more detail by reading through the various tutorials (and experimenting)
Concurrency
Creating a GUI With JFC/Swing
Concurrency in Swing
Worker Threads and SwingWorker
How to Use Actions
How to Use Key Bindings
The example presents two ways to execute the "loop" (which is presented in the doInBackground method of the CalculateWorker class).
You can press and hold the JButton or press and hold the [kbd]Space[kbd] bar, both will cause the "main loop" to run, updating the JTextArea with the results...
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.KeyStroke;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea ta;
private CalculateWorker worker;
public TestPane() {
setLayout(new BorderLayout());
ta = new JTextArea(20, 20);
ta.setEditable(false);
add(new JScrollPane(ta));
worker = new CalculateWorker(ta);
JButton btn = new JButton("Press");
btn.getModel().addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent e) {
System.out.println("...isRunning = " + worker.isRunning());
if (!worker.isRunning()) {
return;
}
System.out.println("...isPressed = " + btn.getModel().isPressed());
System.out.println("...isPaused = " + worker.isPaused());
if (btn.getModel().isPressed()) {
worker.pause(false);
} else {
worker.pause(true);
}
}
});
add(btn, BorderLayout.SOUTH);
worker.execute();
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0, false), "Space.released");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0, true), "Space.pressed");
am.put("Space.released", new CalculateAction(false, worker));
am.put("Space.pressed", new CalculateAction(true, worker));
}
public class CalculateWorker extends SwingWorker<List<String>, String> {
private AtomicBoolean run = new AtomicBoolean(true);
private AtomicBoolean paused = new AtomicBoolean(false);
private ReentrantLock pausedLocked = new ReentrantLock();
private Condition pausedCondition = pausedLocked.newCondition();
private JTextArea ta;
public CalculateWorker(JTextArea ta) {
this.ta = ta;
pause(true);
}
public void stop() {
run.set(false);
pausedLocked.lock();
pausedCondition.signalAll();
pausedLocked.unlock();
}
public void pause(boolean pause) {
paused.set(pause);
pausedLocked.lock();
pausedCondition.signalAll();
pausedLocked.unlock();
}
public boolean isPaused() {
return paused.get();
}
public boolean isRunning() {
return run.get();
}
#Override
protected List<String> doInBackground() throws Exception {
List<String> values = new ArrayList<>(256);
long value = 0;
System.out.println("!! Start running");
while (run.get()) {
while (paused.get()) {
System.out.println("!! I'm paused");
pausedLocked.lock();
try {
pausedCondition.await();
} finally {
pausedLocked.unlock();
}
}
System.out.println("!! Start loop");
while (!paused.get() && run.get()) {
value++;
values.add(Long.toString(value));
publish(Long.toString(value));
Thread.sleep(5);
}
System.out.println("!! Main loop over");
}
System.out.println("!! Run is over");
return values;
}
#Override
protected void process(List<String> chunks) {
for (String value : chunks) {
ta.append(value);
ta.append("\n");
}
ta.setCaretPosition(ta.getText().length());
}
}
public class CalculateAction extends AbstractAction {
private boolean start;
private CalculateWorker worker;
public CalculateAction(boolean start, CalculateWorker worker) {
putValue(NAME, "Calculate");
this.start = start;
this.worker = worker;
}
#Override
public void actionPerformed(ActionEvent e) {
worker.pause(start);
}
}
}
}
Is there a simpler solution?
Of course, I always go for the most difficult, hard to understand solutions first (sarcasm)
While it "might" be possible to reduce the complexity, the example presents a number of "best practice" concepts which you would do well to learn and understand.
The solution could also be done differently depending on the API used, so, it's the "simplest" solution for the specific API choice.
I wanted to do it from the console!
Java can't do that - it's console support is rudimentary at best and doesn't support a concept of "key pressed/released" actions (since it's running in a single thread, it would be impossible for it to do otherwise).
There "are" solutions you might try, but they would require a third party library linked to native binaries to implement, which would (possibly) reduce the number of platforms it would run on

How to stop the main thread and wait until an opened popup form disposes in JAVA?

I have 2 classes: control and popup. I run a loop to and call 3 jframe forms.
I want on the main control class, it must stop and wait until a popup disposes before continue the loop and open another one. How can I achieve this?
I tried to create add an extraThread to run the popup and use extraThread.join() but it still doesn't work.
control
package main;
public class control {
public static void main(String[] args) {
for(int i = 0; i < 3; i++) {
popup pop = new popup();
System.out.println("" + i);
pop.show();
}
}
}
popup
package main;
import java.awt.SystemColor;
import javax.swing.JFrame;
public class popup {
private JFrame frmpopup;
public popup() {
initialize();
}
private void initialize() {
frmpopup = new JFrame();
frmpopup.getContentPane().setBackground(SystemColor.controlHighlight);
frmpopup.setTitle("Standard Form");
frmpopup.setBounds(100, 100, 224, 269);
frmpopup.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
}
public void show() {
frmpopup.setVisible(true);
}
}

I would prefer using in-build method for Jframe to know its status.
You could do something like this.
public class MyTest {
public static void main(String[] args) throws InterruptedException {
for (int i = 0; i < 3; i++) {
popup pop = new popup();
System.out.println("" + i);
pop.show();
while (pop.isDisplayed()) {
// waiting
Thread.sleep(1000); // you could remove this as well
}
}
}
}
popup class
class popup {
private JFrame frmpopup;
public popup() {
initialize();
}
private void initialize() {
frmpopup = new JFrame();
frmpopup.getContentPane().setBackground(SystemColor.controlHighlight);
frmpopup.setTitle("Standard Form");
frmpopup.setBounds(100, 100, 224, 269);
frmpopup.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
}
public void show() {
frmpopup.setVisible(true);
}
public boolean isDisplayed() {
if (frmpopup.isDisplayable())
return true;
else
return false;
}
}

Query on creating separate thread in java?

Below is the compiled program replica of actual problem code,
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
public class Dummy {
public static boolean getUserCheck(int size, boolean Check) {
if (Check) {
int ret = JOptionPane.showConfirmDialog(null, size + " entries, Yes or no?",
"Warning", 0);
if (ret > 0) {
System.out.println("User said No: " + ret);
return false;
} else if (ret <= 0) {
System.out.println("user said Yes: " + ret);
return true;
}
}
return true;
}
public static void workerMethod1() {
System.out.println("am worker method 1");
}
public static void workerMethod2() {
System.out.println("am worker method 2");
}
public static void main(String[] args) {
System.out.println("mainthread code line 1");
int size = 13;
boolean thresholdBreach = true;
if (getUserCheck(size, thresholdBreach)) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
workerMethod1();
}
});
SwingUtilities.invokeLater(new Runnable() {
public void run() {
workerMethod2();
}
});
}
System.out.println("mainthread code line 2");
System.out.println("mainthread code line 3");
}
}
where i would like to run the if{} block in main() on separate thread. Because these 2 lines,
System.out.println("mainthread code line 2");
System.out.println("mainthread code line 3");
need not wait for completion of if(){} block
Another problem is, experts recommend to run confirm-dialog methods on event thread.
int ret = JOptionPane.showConfirmDialog(null, size + " entries, Yes or no?",
"Warning", 0);
Please help me!!!!

JOptionPane is a Swing method and should be called on the EDT, the Event Dispatch Thread, and only on this thread, and so it suggests that all your code above should be on the EDT, and that most of your SwingUtilities.invokeLater(new Runnable() calls are completely unnecessary. The only necessary ones will be the main one, where you launch your Swing GUI code, and any areas where Swing calls need to be made from within background threads. Again, if any of the above code is being made within background threads, then the JOptionPane should not be in that thread.
For more specific information in this or any other answer, please provide more specific information in your question. Let's end all confusion. The best way to get us to fully and quickly understand your problem would be if you were to to create and post a minimal example program, a small but complete program that only has necessary code to demonstrate your problem, that we can copy, paste, compile and run without modification.
I have a sneaking suspicion that a decent refactoring along MVC lines could solve most of your problems. Your code is very linear with its lines of code that must follow one another and its if blocks, and it is also tightly coupled with your GUI, two red flags for me. Perhaps better would be less linear code, more event and state-driven code, code where your background code interacts with the GUI via observer notification, and where the background code likewise responds to state changes in the GUI from control notification.
Your control needs two SwingWorkers, one to get the row count and the other to get the rest of the data if the user decides to do so. I'd add a PropertyChangeListener to the first SwingWorker to be notified when the row count data is ready, and then once it is, present it to the view for the user to select whether or not to proceed. If he decides to proceed, I'd then call the 2nd SwingWorker to get the main body of the data.
For example, a rough sketch of what I'm talking about:
import java.awt.Dialog.ModalityType;
import java.awt.Dimension;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ExecutionException;
import javax.swing.*;
#SuppressWarnings("serial")
public class SwingWorkerFooView extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = 300;
private JProgressBar progressBar;
private JDialog dialog;
public SwingWorkerFooView() {
add(new JButton(new ButtonAction("Foo", this)));
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
public boolean showOptionGetAllData(int numberOfRows) {
String message = "Number of rows = " + numberOfRows + ". Get all of the data?";
String title = "Get All Of Data?";
int optionType = JOptionPane.YES_NO_OPTION;
int result = JOptionPane.showConfirmDialog(this, message, title, optionType);
return result == JOptionPane.YES_OPTION;
}
public void showProgressBarDialog() {
progressBar = new JProgressBar();
progressBar.setIndeterminate(true);
Window window = SwingUtilities.getWindowAncestor(this);
dialog = new JDialog(window, "Hang on", ModalityType.APPLICATION_MODAL);
JPanel panel = new JPanel();
panel.add(progressBar);
dialog.add(panel);
dialog.pack();
dialog.setLocationRelativeTo(this);
dialog.setVisible(true);
}
public void closeProgressBarDialog() {
dialog.dispose();
}
private static void createAndShowGui() {
JFrame frame = new JFrame("SwingWorkerFoo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new SwingWorkerFooView());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
#SuppressWarnings("serial")
class ButtonAction extends AbstractAction {
Workers workers = new Workers();
private SwingWorker<Integer, Void> firstWorker;
private SwingWorker<List<String>, Void> secondWorker;
private SwingWorkerFooView mainGui;
public ButtonAction(String name, SwingWorkerFooView mainGui) {
super(name);
this.mainGui = mainGui;
}
#Override
public void actionPerformed(ActionEvent e) {
firstWorker = workers.createFirstWorker();
firstWorker.addPropertyChangeListener(new FirstPropertyChangeListener());
firstWorker.execute();
mainGui.showProgressBarDialog();
}
private class FirstPropertyChangeListener implements PropertyChangeListener {
#Override
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
mainGui.closeProgressBarDialog();
try {
int numberOfRows = firstWorker.get();
boolean getAllData = mainGui.showOptionGetAllData(numberOfRows);
if (getAllData) {
secondWorker = workers.createSecondWorker();
secondWorker.addPropertyChangeListener(new SecondPropertyChangeListener());
secondWorker.execute();
mainGui.showProgressBarDialog();
} else {
// user decided not to get all data
workers.cleanUp();
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}
}
private class SecondPropertyChangeListener implements PropertyChangeListener {
#Override
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
mainGui.closeProgressBarDialog();
try {
List<String> finalData = secondWorker.get();
// display finalData in the GUI
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}
}
}
class Workers {
// database object that may be shared by two SwingWorkers
private Object someDataBaseVariable;
private Random random = new Random(); // just for simulation purposes
private class FirstWorker extends SwingWorker<Integer, Void> {
#Override
protected Integer doInBackground() throws Exception {
// The Thread.sleep(...) is not going to be in final production code
// it's just to simulate a long running task
Thread.sleep(4000);
// here we create our database object and check how many rows there are
int rows = random.nextInt(10 + 10); // this is just for demonstration purposes only
// here we create any objects that must be shared by both SwingWorkers
// and they will be saved in a field of Workers
someDataBaseVariable = "Fubar";
return rows;
}
}
private class SecondWorker extends SwingWorker<List<String>, Void> {
#Override
protected List<String> doInBackground() throws Exception {
// The Thread.sleep(...) is not going to be in final production code
// it's just to simulate a long running task
Thread.sleep(4000);
List<String> myList = new ArrayList<>();
// here we go through the database filling the myList collection
return myList;
}
}
public SwingWorker<Integer, Void> createFirstWorker() {
return new FirstWorker();
}
public void cleanUp() {
// TODO clean up any resources and database stuff that will not be used.
}
public SwingWorker<List<String>, Void> createSecondWorker() {
return new SecondWorker();
}
}
The key to all of this is to not to think in a linear console program way but rather to use observer design pattern, i.e., listeners of some sort to check for change of state of both the GUI and the model.
It's essentially:
create worker
add observer to worker (property change listener)
execute worker
show progress bar dialog or notify user in some way that worker is executing.
The listener will be notified when the worker is done, and then you can query the worker (here via the get() method call) as to its end result.
Then the progress dialog can be closed
And the view can display the result or get additional information from the user.

Yes; SwingUtilities.invokeLater() simply places your runnable on the AWT event queue to be processed later, and it is safe to do so at any time.

Using a thread loop to update a JFrame

ive done some extensive searching on using threads in a loop and whilst I understand the concept how how seperate threads work, I still cant seem to grasp how to implement it in my simple application.
My application consists of a form with a text box. This textbox needs to be updated once ever iteration of a loop. It starts with the press of a button but the loop should also finish with the press of a stop button. Ive used a boolean value to track if its been pressed.
Here is my form code:
package threadtester;
public class MainForm extends javax.swing.JFrame {
public MainForm() {
initComponents();
}
private void RunButtonActionPerformed(java.awt.event.ActionEvent evt) {
ThreadTester.setRunnable(true);
ThreadTester example = new ThreadTester(2,this);
example.run();
}
private void StopButtonActionPerformed(java.awt.event.ActionEvent evt) {
ThreadTester.setRunnable(false);
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MainForm().setVisible(true);
}
});
}
public void setTextBox(String myString){
MainTextbox.setText(myString);
}
}
As you can see I have a button that is pressed. When the button is pressed this executes the code thats in a different class called ThreadTester. Here is the code for that class:
package threadtester;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ThreadTester implements Runnable
{
int thisThread;
MainForm myMainForm;
private static boolean runnable;
// constructor
public ThreadTester (int number,MainForm mainForm)
{
thisThread = number;
myMainForm = mainForm;
}
public void run ()
{
for (int i =0;i< 20; i++) {
if(runnable==false){
break;
}
System.out.println("I'm in thread " + thisThread + " line " + i);
myMainForm.setTextBox(i + "counter");
try {
Thread.sleep(1000);
} catch (InterruptedException ex) {
Logger.getLogger(ThreadTester.class.getName()).log(Level.SEVERE, null, ex);
}
} }
public static void setRunnable(Boolean myValue){
runnable = myValue;
}
public static void main(String[] args) {
MainForm.main(args);
}
}
as you can see the loop has been created on a seperate thread... but the textbox only updates after the loop has finished. Now as far as im aware in my MainForm I created a seperate thread to run the loop on, so I dont understand why its not running? Any guidence would be much appreciated, ive tried looking at examples on stack exchange but I cant seem to get them to fit into my implemntation.
With the recommendation suggested by Tassos my run method now looks like this:
public void run ()
{
for (int i =0;i< 20; i++) {
if(runnable==false){
break;
}
System.out.println("I'm in thread " + thisThread + " line " + i);
final String var = i + "counter";
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
myMainForm.setTextBox(var);
}
});
try {
Thread.sleep(1000);
} catch (InterruptedException ex) {
Logger.getLogger(ThreadTester.class.getName()).log(Level.SEVERE, null, ex);
}
} }

In order for Tassos' answer to work, you actually have to create an new thread, which you did not do. Simply calling
ThreadTester example = new ThreadTester(2,this);
example.run();
is not enough, sice that just calls the run method from EDT. You need to do the following:
Thread t = new Thread(new ThreadTester(2,this));
t.start();
Please refer to Defining and Starting a Thread.
Also, you want modify the same field from two different threads (runnable), which is a bug. You should read more about java concurrency.

Change this line
myMainForm.setTextBox(i + "counter");
into
final String var = i + "counter";
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
myMainForm.setTextBox(var);
}
});
}
Why? Because you can't do UI work in non-UI threads.

The problem is that you are blocking the EDT (Event Dispatching Thread), preventing the UI to refresh until your loop is finished.
The solutions to these issues is always the same, use a Swing Timer or use a SwingWorker.
Here is an example of the usage of a SwingWorker:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class TestSwingWorker {
private JTextField progressTextField;
protected void initUI() {
final JFrame frame = new JFrame();
frame.setTitle(TestSwingWorker.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton button = new JButton("Clik me to start work");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
doWork();
}
});
progressTextField = new JTextField(25);
progressTextField.setEditable(false);
frame.add(progressTextField, BorderLayout.NORTH);
frame.add(button, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
protected void doWork() {
SwingWorker<Void, Integer> worker = new SwingWorker<Void, Integer>() {
#Override
protected Void doInBackground() throws Exception {
// Here not in the EDT
for (int i = 0; i < 100; i++) {
// Simulates work
Thread.sleep(10);
publish(i); // published values are passed to the #process(List) method
}
return null;
}
#Override
protected void process(List<Integer> chunks) {
// chunks are values retrieved from #publish()
// Here we are on the EDT and can safely update the UI
progressTextField.setText(chunks.get(chunks.size() - 1).toString());
}
#Override
protected void done() {
// Invoked when the SwingWorker has finished
// We are on the EDT, we can safely update the UI
progressTextField.setText("Done");
}
};
worker.execute();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestSwingWorker().initUI();
}
});
}
}

Changing JTextField's text while iterating or inside a loop [duplicate]

This question already has answers here:
updating a JProgressBar while processing
(2 answers)
Closed 9 years ago.
Let's say I have a JTextField "status" and I'm running this code:
status = new JTextField(50);
add(status);
for (int i=0; i<10000; i++) {
status.setText("bla bla - "+ i);
System.out.println("bla bla - "+ i);
}
My problem is that right now while the loop is running nothing happened in the JTextField's text and only when the loop end the label is "bla bla - 10000".
I want to make something like a status bar but cant update this status bar "online".
I also tried to do the update in a thread but ended with the same result.
Can someone show my how I can present a text in a GUI while iterating or looping?

Use a SwingWorker to split UI-update and long running tasks.
Take a few minutes to read the end of the Swing tag wiki and follow the provided links.
Here is a small example of such code:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class TestSwingWorker {
private JTextField progressTextField;
protected void initUI() {
final JFrame frame = new JFrame();
frame.setTitle(TestSwingWorker.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton button = new JButton("Clik me to start work");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
doWork();
}
});
progressTextField = new JTextField(25);
progressTextField.setEditable(false);
frame.add(progressTextField, BorderLayout.NORTH);
frame.add(button, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
protected void doWork() {
SwingWorker<Void, Integer> worker = new SwingWorker<Void, Integer>() {
#Override
protected Void doInBackground() throws Exception {
for (int i = 0; i < 100; i++) {
// Simulates work
Thread.sleep(10);
publish(i);
}
return null;
}
#Override
protected void process(List<Integer> chunks) {
progressTextField.setText(chunks.get(chunks.size() - 1).toString());
}
#Override
protected void done() {
progressTextField.setText("Done");
}
};
worker.execute();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new TestSwingWorker().initUI();
}
});
}
}

Use a javax.swing.Timer. Here is an example that shows you how:
private void refreshMyTextField() {
Timer timer1 = new Timer(100, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
jTextField1.setText("bla bla - "+(j++));
}
});
timer1.start();
}

Use Timer class which executes a task in intervals. Because you don't use interval, what you get is the last value 10000. You can't see previous values because of interval absence.
Regards,

try to use status.setText(""); before status.setText("bla bla - "+ i);