Re: How to change JPanels?

Lew <>
Mon, 14 Feb 2011 16:50:07 -0500
On 02/14/2011 03:02 PM, Eric wrote:

So now my previous sample looks like this. I hope I'm doing this
right now. I'm not sure if it's the most efficient syntax but it

... imports elided ...
public class TestWindow {

      InnerTestWindow win = null;

      protected class InnerTestWindow extends JFrame {

           protected CardLayout cardLayout = null;
           protected Container contentPane = null;
           protected JPanel panelOne = null;
           protected JPanel panelTwo = null;
           private JTextArea dummyTextOne = null;
           private JTextArea dummyTextTwo = null;

           protected InnerTestWindow() {
                contentPane = getContentPane();
                contentPane.setLayout(new CardLayout());
                cardLayout = (CardLayout)contentPane.getLayout();
                MenuBar menuBar = new MenuBar();
                Menu menu = new Menu("Test");

setDefaultCloseOperation( WindowConstants.DISPOSE_ON_CLOSE );
                setSize(600, 600);
                setLocation(100, 100);
                panelOne = new JPanel();
                contentPane.add(panelOne,"Panel One");
                dummyTextOne = new JTextArea("Panel One");
                panelTwo = new JPanel();
                contentPane.add(panelTwo,"Panel Two");
                dummyTextTwo = new JTextArea("Panel Two");

           private void addMenuItem(Menu menu, String menuItemTitle,
String menuItemName, ActionListener menuListener) {
                MenuItem menuItem = new MenuItem(menuItemTitle);

           protected class FirstItemWorker extends SwingWorker {
                BufferedImage[] renderedPngPages = null;
                int waitTime;
                protected FirstItemWorker(int waitTimeIn) {
                     waitTime = waitTimeIn;
                protected Integer doInBackground() {
                     long t0, t1;
                     t0 = System.currentTimeMillis();
                     do {
                          t1 = System.currentTimeMillis();
                     } while ((t1 - t0)< (waitTime));
                     return 0;
                protected void done() {
                     if (isCancelled()) {

           private class FirstItemListener implements ActionListener {
                public void actionPerformed(ActionEvent ev) {
                     FirstItemWorker fiw = new FirstItemWorker(3000);

           protected void loadOne() {
      , "Panel One");

           public void loadTwo() {
      , "Panel Two");

      public void createWindow() {
           win = new InnerTestWindow();

      public static void main(String[] args) throws Exception {
           TestWindow testWin = new TestWindow();


You need to construct and stasrt your 'TestWindow' instance on the EDT, as
others have warned you.

Not sure why you feel the need to initialize member variables to 'null' that
are already initialized to 'null', but they're your wasted keystrokes and
microseconds of redundant initialization.

You might want to use 'sleep()' or a variant instead of a CPU-gobbling tight
loop for the 'doInBackground()'.

Honi soit qui mal y pense.

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