How to Display an Indeterminate Progress Bar While Running a Batch File in Java?

Displaying an Indeterminate Progress Bar While Running a Batch File

In desktop applications, it's crucial to provide visual feedback to users while lengthy tasks are underway. When running batch files in the background, a common issue arises - the screen appears idle, leaving users unsure if the program is still running. To address this, displaying an indeterminate progress bar can alleviate confusion and enhance the user experience.

Challenges with Swing

Swing is a popular Java GUI toolkit, but it faces limitations when handling multiple processes and updating UI elements from non-EDT threads. While it's possible to use a SwingWorker to execute tasks in the background, it's not designed to handle the output of the batch file.

A Better Solution Using ProcessBuilder

ProcessBuilder offers a more robust approach. You can run the batch file in the background using ProcessBuilder.start(), then monitor its progress and obtain its output through standard streams. Additionally, by implementing a SwingWorker, you can update the progress bar from the EDT thread, ensuring a responsive GUI.

An Example Implementation

The following code example demonstrates how to use ProcessBuilder with SwingWorker to display an indeterminate progress bar while running a batch file:

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.swing.*;

public class BatchFileProgress {

    private final JLabel statusLabel = new JLabel("Status: ", JLabel.CENTER);
    private final JTextArea textArea = new JTextArea(20, 20);
    private JButton startButton = new JButton("Start");
    private JButton stopButton = new JButton("Stop");
    private JProgressBar bar = new JProgressBar();
    private BackgroundTask backgroundTask;
    private final ActionListener buttonActions = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            JButton source = (JButton) ae.getSource();
            if (source == startButton) {
                textArea.setText(null);
                startButton.setEnabled(false);
                stopButton.setEnabled(true);
                backgroundTask = new BackgroundTask();
                backgroundTask.execute();
                bar.setIndeterminate(true);
            } else if (source == stopButton) {
                backgroundTask.cancel(true);
                backgroundTask.done();
            }
        }
    };

    private void displayGUI() {
        JFrame frame = new JFrame("Batch File Progress");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setBorder(
            BorderFactory.createEmptyBorder(5, 5, 5, 5));
        panel.setLayout(new BorderLayout(5, 5));

        JScrollPane sp = new JScrollPane();

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