Question

Ok, I have the following code.

public class MyProgressBar extends JPanel implements MyData, Serializable {

    /**
     * 
     */

    public static final int MAX                = 10000;
    public static final int WIDTH              = 400;
    public static final int HEIGHT             = 75;

    private JProgressBar    MyBar              = new JProgressBar( SwingConstants.HORIZONTAL, 0, MAX );
    private JFrame          MyFrame            = new JFrame();

    private int             MyValue            = 0;

    private Thread          MyThread           = new Thread( new ProgressThread() );



    public MyProgressBar() {
        add(MyBar);

        int x = ( MyData.SCREEN.width  / 2 ) - ( WIDTH  / 2);
        int y = ( MyData.SCREEN.height / 2 ) - ( HEIGHT / 2);

        this.setBounds( x, y, WIDTH, HEIGHT );

        MyFrame.setBounds( x, y, WIDTH, HEIGHT );
        MyFrame.setUndecorated(true);
        MyFrame.getContentPane().setSize( new Dimension( WIDTH, HEIGHT ) );
        MyFrame.setMinimumSize( new Dimension( WIDTH, HEIGHT ) );
        MyFrame.setPreferredSize( new Dimension( WIDTH, HEIGHT ) );
        MyFrame.setSize( new Dimension( WIDTH, HEIGHT ) );
        MyFrame.setVisible(false);
        MyFrame.getContentPane().setLayout(null);

        MyBar.setStringPainted( true );
        MyBar.setBorderPainted( true );
        MyBar.setValue( 0 );
        MyBar.setBounds( 0, 0, WIDTH, HEIGHT );

        MyFrame.add( MyBar );
        MyFrame.pack();
        MyFrame.repaint();

    }

    public void MyUpdateBar() {
        MyBar.setValue( MyValue );
        MyBar.repaint();
        MyFrame.repaint();
        this.repaint();
        //dbug.Message( "MYPROGRESSBAR", "MyUpdateBar", "Value is %3.2f %d", MyBar.getPercentComplete(), MyValue );
    }

    public void MySetValue( int percent ) {
        MyValue = (int)( MAX * ( (double)percent / 100.0 ) );
        MyUpdateBar();
        //dbug.Message( "MYPROGRESSBAR", "MySetValue", "Value is %3.2f %d percent was %d", MyBar.getPercentComplete(), MyValue, percent );
    }

    public void CreateAndShow () {
        MyFrame.setVisible(true);
        MyThread.start();
    }

    public void HideAndClear () {
        MyThread.stop();
        //frame.setVisible(false);
    }

    class ProgressThread implements Runnable {
        public void run() {
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    while( MyValue < MyBar.getMaximum() ) {
                        MyBar.setValue( MyValue );
                        MyBar.repaint();
                        MyFrame.repaint();
                        dbug.Message( "MYPROGRESSBAR", "THREAD", "Value is %3.2f %d", MyBar.getPercentComplete(), MyValue );
                    }
                }
            });
        }

    }



}

As you can see, I have created a class that I want to have show the progress. What happens is I instantiate the class. Load my XML file, then as I am parsing data, I am calling to update the MyValue which I see when I let my dbug messages come out. However, the bar itself does not even show until it is 100% complete. I have read about threading and following someone else’s example and if I left it as his example it worked. If I made a few tweaks (changing a loop in the thread to populate the setvalue of the progress bar to read a value) it does not even show until it is 100.

What did I do wrong?

Thanks!

Answer 1

You thread executes SwingUtilities.invokeLater. You’re effectively running on Swing’s Event Dispatch Thread. Not sure what are you trying to achieve. But it looks like you are blocking EDT and your while loop is not updated as MySetValue is not executed.

Consider using SwingWorker for lengthy operations. How to Use Progress Bars demonstrates use of SwingWorker with JProgressBar.

Make sure you call setValue method from the Event Dispatch Thread. You can use SwingUtilities.invokeLater for that. Read more about Threads and Swing.

Consider this simplified sample:

public static void main(String[] arguments) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);

    final JProgressBar bar = new JProgressBar(0, 100);

    Thread t = new Thread(){
        public void run(){
            for(int i = 0 ; i < 100 ; i++){
                final int percent = i;
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        bar.setValue(percent);
                    }
                  });

                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {}
            }
        }
    };
    frame.add(bar);
    frame.pack();
    frame.setVisible(true);
    t.start();
}