Javax.swing: how to display updates to components properly?

Question

I'm writing a simple Knight's Tour program with a graphical display. I've already written it to work with the console, and now I'm trying to transfer that code over so that it works with swing. I've got a button whose Action Listener starts and operates the process. Here is the code:

askButton.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e) {

            int[][] tour = getBoard(); // generates a matrix representing a successful knight's tour
            int count = 0;

            while (count < 64) {
                count++;
                Location loc = searchFor(count, tour); //gets the location of the int "count" inside the matrix "tour"
                board.setVisible(false); //board contains a matrix of JPanels called "grid".
                grid[loc.row()][loc.column()].add(new JLabel("" + count)); //adds JLabel to JPanel with the proper number
                board.setVisible(true); //reset to visible to show changes
                delay(1000); //wait 1000 milliseconds - one second - to allow user to view changes
            }
        }
    });

So that is the code. I want each number to show up individually with one second intervals in between, but as it stands, the frame becomes blank for a while and suddenly displays the results with all the numbers showing, once finished. Could someone please help? Thank you.

Answer 1

put all answers here together

1.don't call sleep(int) , wait(int) during code executed from AWT / Swing Listener , use

• Swing Timer instead,

or

• all output to the Swing GUI must be wrapped inside invokeLater in code your nature

2.after add / remove / modify already visible container is required to call

• revalidate() and repaint() , thenafter setVisible()

3. setVisible must be wrapped inside invokeLater in code your nature

Answer 2

Your delay method blocks the Event Dispatch Thread, avoiding repaints of those components. Take a look at the Swing Concurrency Tutorial for more information on Swing and threads.

A possible solution for your problem is the use of a Swing Timer instead of the delay method

Answer 3

When you are in that while loop, repaint() is never called. That would be why you don't see anything until the method ends.

Answer 4

First of all, try to call revalidate() and repaint() after you make some change on the GUI. Second, I also had a GUI project which is similar to yours as my CSE assisnment.

During the process, I find that the GUI is not update simultaneously as I wanted. I tried many ways of working it out. The final solution is that give up using add JLabels or JPanels on the board(JFrame), instead, using setIcon or setText to have a better communication with the frame. Well, this is just my personally experience. Hope could of help for your project.