How to Continuously Update a JLabel Using Swing Timer and SwingWorker?

Using Swing Timer and SwingWorker to Update JLabel Continuously

In order to regularly update a JLabel with the results of a time-consuming activity, it is recommended to employ both a Swing Timer and a SwingWorker. The Swing Timer handles recurring tasks, while the SwingWorker manages time-consuming undertakings. Here's a sample code that illustrates how this strategy functions:

<code class="java">import java.awt.event.*;
import javax.swing.*;
import java.net.Socket;

public class LabelUpdateUsingTimer {

    static String hostnameOrIP = "stackoverflow.com";
    int delay = 5000;
    JLabel label = new JLabel("0000");

    LabelUpdateUsingTimer() {
        label.setFont(label.getFont().deriveFont(120f));

        ActionListener timerListener = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                new PingWorker().execute();
            }
        };
        Timer timer = new Timer(delay, timerListener);

        timer.start();
        JOptionPane.showMessageDialog(
                null, label, hostnameOrIP, JOptionPane.INFORMATION_MESSAGE);
        timer.stop();
    }

    class PingWorker extends SwingWorker {

        int time;

        @Override
        protected Object doInBackground() throws Exception {
            time = pingTime();
            return new Integer(time);
        }

        @Override
        protected void done() {
            label.setText("" + time);
        }
    };

    public static int pingTime() {
        Socket socket = null;
        long start = System.currentTimeMillis();
        try {
            socket = new Socket(hostnameOrIP, 80);
        } catch (Exception weTried) {
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (Exception weTried) {}
            }
        }
        long end = System.currentTimeMillis();
        return (int) (end - start);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                new LabelUpdateUsingTimer();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}</code>

For more details regarding the Event Dispatch Thread and executing repetitive or extended tasks in a GUI, please consult the Concurrency in Swing document.

How the Code Works:

1. Initialization: The LabelUpdateUsingTimer constructor initializes a JLabel named label and sets its font.
2. ActionListener and Timer: An ActionListener called timerListener is created, and it will trigger the execution of the PingWorker every delay milliseconds. A Timer object is then initiated using the delay and timerListener as arguments, and it is subsequently started.
3. JOptionPane: The JLabel is displayed within an JOptionPane dialog box with the specified hostnameOrIP.
4. PingWorker: The PingWorker class, a SwingWorker subclass, performs the time-consuming operation in a background thread.
5. Ping Time: The pingTime method establishes a TCP connection to the specified hostnameOrIP and calculates the latency.

By employing this technique, you can continuously update a JLabel with the latest results of a time-consuming task, enabling real-time monitoring and user interaction.

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