Unable to update GUI while sending file

Question

I am sending a file over network using sockets. The file is received properly without any problem. But now I am using a JProgressBar to show percentage of file sent. My problem is that even when I update GUI in a separate thread, the progress bar is updated only when file is completely sent. I also tried adjusting the priority of main thread to Thread.MIN_PRIORITY but the problem still persisted.

The complete code is long so I am not posting it (I will post if someone asks). The short code for sending file and updating progress bar is

final double temp=(done/fileSize)*100; // percentage of file sent
SwingUtilities.invokeLater(new Runnable()
{
    public void run()
    {
        try
        {
            jpb.setString("Completed : "+temp+" %");
            jpb.setValue((int)temp); // this is executed only when 100%
        }      
        catch(Exception e) 
        {
            e.printStackTrace();
        }
    }
});
System.out.println(temp); // only this and
bos.write(b,0,read);      // this statement is executed

Answer 1

Problem lies in below line:

final double temp=(done/fileSize)*100; // percentage of file sent

If done and fileSize are both not double then result of done/fileSize is 0.0.

Make them double (at least one of them) to keep the decimal part of the division.

Answer 2

Here is a implementation that I talked about.

It's not the best design as I did it quick and dirty but this way the file transfer code is not dependent on the UI.

public class FileTransfer implements Runnable
{
    double transferPercent = 0.0;

    double getTransferPercent(){ return transferPercent; }

    @Override
    public void run()
    {
        while(transferingFile)
        {
            // Write data
            // Update transferPercent
        }
    }
}

public class UIClass extends TimerTask
{
    private FileTransfer fileTransfer;

    public void createUI()
    {
        TimerTask myClass = this;
        JButton b = new JButton("Transfer");
        b.addMouseListener(new MouseAdapter()
        {
            @Override
            public void mouseClicked(MouseEvent e)
            {
                fileTransfer.start();
                Timer t = new Timer();
                t.scheduleAtFixedRate(myClass, 0.0, 20);
            }
        });
    }

    // Update the UI here!
    @Override
    public void run()
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                jpb.setValue(fileTransfer.getTransferPercent());
            }
        });
    }
}

Answer 3

I'd probably design this differently. I'd make the network code independent of the UI and have it just update a variable on percentage sent.

The UI would then poll this number with a timer to update the progress bar.

But your code should work. Try adding an @Override on your run function. Maybe SwingUltities.invokeLater is calling Runnable's run function instead of your own.