ProgressBar is not working

Question

Hello! I am trying to indicate ProgressBar during download the binary file. But ProgressBar is not working.Please help me!
* BinarySaver6.java
* Created on 2003/08/30, 14:46
import java.net.*;
import java.io.*;
* @author masaki
public class BinarySaver6 extends javax.swing.JFrame {
/** Creates new form BinarySaver6 */
public BinarySaver6() {
initComponents();
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
private void initComponents() {//GEN-BEGIN:initComponents
jTextField1 = new javax.swing.JTextField();
jButton1 = new javax.swing.JButton();
jProgressBar1 = new javax.swing.JProgressBar();
addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent evt) {
exitForm(evt);
jTextField1.setText("http://");
getContentPane().add(jTextField1, java.awt.BorderLayout.NORTH);
jButton1.setText("DOWNLOAD");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
getContentPane().add(jButton1, java.awt.BorderLayout.CENTER);
jProgressBar1.setStringPainted(true);
getContentPane().add(jProgressBar1, java.awt.BorderLayout.SOUTH);
pack();
}//GEN-END:initComponents
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
try {
URL u = new URL(jTextField1.getText());
URLConnection uc = u.openConnection();
String contentType = uc.getContentType();
int contentLength = uc.getContentLength();
if (contentType.startsWith("text/") || contentLength == -1 ) {
throw new IOException("This is not a binary file.");
InputStream raw = uc.getInputStream();
InputStream in = new BufferedInputStream(raw);
byte[] data = new byte[contentLength];
int bytesRead = 0;
int offset = 0;
while (offset < contentLength) {
bytesRead = in.read(data, offset, data.length-offset);
if (bytesRead == -1) break;
offset += bytesRead;
     jProgressBar1.setValue(jProgressBar1.getValue()+offset);
in.close();
if (offset != contentLength) {
throw new IOException("Only read " + offset
+ " bytes; Expected " + contentLength + " bytes");
String filename = u.getFile();
filename = filename.substring(filename.lastIndexOf('/') + 1);
FileOutputStream fout = new FileOutputStream(filename);
fout.write(data);
fout.flush();
fout.close();
catch (MalformedURLException e1) {
System.err.println(jTextField1.getText() + " is not URL I understand.");
catch (IOException e2) {
System.err.println("error");
}//GEN-LAST:event_jButton1ActionPerformed
/** Exit the Application */
private void exitForm(java.awt.event.WindowEvent evt) {//GEN-FIRST:event_exitForm
System.exit(0);
}//GEN-LAST:event_exitForm
* @param args the command line arguments
public static void main(String args[]) {
new BinarySaver6().show();
// �������� - ���W�s��//GEN-BEGIN:variables
private javax.swing.JTextField jTextField1;
private javax.swing.JButton jButton1;
private javax.swing.JProgressBar jProgressBar1;
// �����������I����//GEN-END:variables

Answer 1

Richard, you like many, many others in the forum on this thread and others fail to appreciate the real problem here, I think. Lot's of people suggest to learn to use threads and read the Swing tutorial on ProgressMonitor. That is good as far as it goes, but consider what we have here. You are right that the problem is that the event processing thread is blocked and that is what is preventing the progress bar from updating. But often what you want to do is exactly to block the event processing thread.
Consider that any application code is full of action handlers etc that manipulate some common data structure(s). Now if you want to do some operation on this data structure you want to block others from manipulating it at the same time. Now if this operation you are doing takes a long time you want to present a progress bar.
How do you do that.
If you just put it up (the progress bar), in a (non modal) window, it won't show. You do not want to put the operation into a thread and let the event processing thread run, as preventing all those other event/action handlers from manipulating the data structures would require a lot of work.
I think that putting the progress bar into a modal dialog (showing the modal dialog would block the event processing thread and thus other action/etc handlers) and creating a separate thread to do the work would work, but seems like a quite a lot of work for something that should be as simple as:
ProgressBarDialog pbar=new ProgressBarDialog());
pbar.setVisible(true);
for (as long as I like)
pbar.setValue(i++)
pbar.setVisible(false);
all this in an actionListener.actionPerformed() method.
I'm just working on that but so far have no code to share...
regs Kusti