Java: A Progress Bar Example Program

Background

The Java code listing shows an example of how to use the JProgressBar and SwingWorker classes. When run the Java application will show a GUI which contains a JButton, a JProgressBar and two JCheckBoxes. The JButton starts a simulated task whose progress is tracked by the JProgressBar. The JCheckBoxes control whether the progress is determined or indeterminate.

Java Code

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JProgressBar;
import javax.swing.JCheckBox;
import javax.swing.JPanel;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.SwingWorker;
import java.awt.BorderLayout;
import java.util.List;
public class ProgressBarExamples {
JProgressBar progressBar;
JCheckBox progressType;
JCheckBox switchType;
final JButton goButton;
//Note: Typically the main method will be in a
//separate class. As this is a simple one class
//example it's all in the one class.
public static void main(String[] args) {
//Use the event dispatch thread for Swing components
EventQueue.invokeLater(new Runnable()
{
@Override
public void run()
{
new ProgressBarExamples();
}
});
}
public ProgressBarExamples()
{
JFrame guiFrame = new JFrame();
//make sure the program exits when the frame closes
guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
guiFrame.setTitle("Creating a Table Example");
guiFrame.setSize(700,200);
//This will center the JFrame in the middle of the screen
guiFrame.setLocationRelativeTo(null);
goButton = new JButton("Go");
goButton.setActionCommand("Go");
goButton.addActionListener(new ActionListener()
{
//When the button is clicked the SwingWorker class is executed and
//the button is disabled
@Override
public void actionPerformed(ActionEvent event)
{
progressBar.setStringPainted(progressType.isSelected());
Sleeper task = new Sleeper();
task.execute();
goButton.setEnabled(false);
}
});
//create a panel to hold the checkboxes
JPanel chkPanel = new JPanel();
//Create a checkbox to pick between a determined or indeterminate
//progressbar
progressType = new JCheckBox("Determined Progress Bar", true);
progressType.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent event)
{
switchType.setEnabled(!progressType.isSelected());
}
});
//Create a checkbox to switch progress bar modes
switchType = new JCheckBox("Switch to Determined");
switchType.setEnabled(false);
chkPanel.add(progressType);
chkPanel.add(switchType);
//create progress bar
progressBar = new JProgressBar(0, 100);
progressBar.setValue(0);
guiFrame.add(goButton, BorderLayout.WEST);
guiFrame.add(progressBar, BorderLayout.CENTER);
guiFrame.add(chkPanel, BorderLayout.SOUTH);
guiFrame.setVisible(true);
}
//SwingWorker class is used to simulate a task being performed
class Sleeper extends SwingWorker {
@Override
public Void doInBackground() throws InterruptedException {
try
{
int progress = 0;
while (progress chunks) {
for (Integer chunk : chunks) {
progressBar.setValue(chunk);
//if the switchtype checkbox is selected then
//change the progressbar to a determined type
//once the progress has reached 50
if (chunk > 49)
{
if (switchType.isEnabled() && switchType.isSelected())
{
progressBar.setStringPainted(true);
}
}
}
}
//when the 'task' has finished re-enable the go button
@Override
public void done() {
goButton.setEnabled(true);
}
}
}