Multithreading program not working

Question

I am trying to make this work. I create a window, with one text field and button, then I run the run() method which should refresh text in textfield, and when I click on button it should iterate number by 1. I want to make this work simultaneously but I am stuck. It just iterates the number but do not refresh a value in textfield.Could you please help me somehow? I thought its easy to learn about Threads but...no :-D Here is the code.

Window class

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton; 
import javax.swing.JFrame;
import javax.swing.JTextField;

@SuppressWarnings("serial") 
public class Okno extends JFrame implements ActionListener,Runnable {

    private JFrame o = new JFrame();
private static JTextField t = new JTextField();
private JTextField t2 = new JTextField();
private static int x = 0;
protected JButton b = new JButton("KLIK");


Okno() {

    o.setVisible(true);
    o.setBounds(0, 0, 300, 200);
    o.setLayout(null);
    o.setDefaultCloseOperation(EXIT_ON_CLOSE);

    t.setBounds(10, 10, 60, 20);
    t2.setBounds(80, 10, 60, 20);
    b.setBounds(50, 80, 60, 30);
    b.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            while (true) {
                Okno.work();
                System.out.println("Klik");
            }

        }
    });
    o.add(t);
    o.add(b);
    o.add(t2);
}
public static int iter(){

    x++;
    return x;
}

public static void work(){
    try {
        iter();
        System.out.println(x);
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
@Override
public void actionPerformed(ActionEvent e) {

}
@Override
public void run() {
    while(true){
        try {
            Thread.sleep(1200);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    t.setText(Integer.toString(x));
    System.out.println("RUN");
    }
}
    }

Main Class

public class ThreadDemo {
public static void main(String args[]) {
 Okno o = new Okno();

 while(true){
 o.run();
 }
 }
 }

Answer 1

Swing is single threaded. Calling Thread.sleep prevents UI updates. Use a Swing Timer instead.

From GETah's answer to java stopwatch that updates gui every second:

Something along these lines should do it:

import java.awt.EventQueue;
import java.util.Timer;
import java.util.TimerTask;
import javax.swing.JFrame;
import javax.swing.JLabel;

/** @see https://stackoverflow.com/a/11058263/230513 */
public class Clock {

    private Timer timer = new Timer();
    private JLabel timeLabel = new JLabel(" ", JLabel.CENTER);

    public Clock() {
        JFrame f = new JFrame("Seconds");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(timeLabel);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
        timer.schedule(new UpdateUITask(), 0, 1000);
    }

    private class UpdateUITask extends TimerTask {

        int nSeconds = 0;

        @Override
        public void run() {
            EventQueue.invokeLater(new Runnable() {

                @Override
                public void run() {
                    timeLabel.setText(String.valueOf(nSeconds++));
                }
            });
        }
    }

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                final Clock clock = new Clock();
            }
        });
    }
}

The timeLabel will always display the number of seconds the timer has been running.

1. You will need to correctly format it to display "hh:mm:ss"; one approach is shown here.

2. Create a container and add the label to it so that you can display it as part of the GUI.

3. Compare the result to this alternate using javax.swing.Timer.