Why wont my JFrame hide ?

Question

I'm in the process of creating a GUI in Netbeans 6.1 for my senior design project but i've run into an annoying snag. Temporary Windows like my login PopUp and others wont disappear when i tell it. I've been researching how to solve this for about 2 months on an off. I've even mad a separate thread for my Pop Up but it still wont work....the only way it will disappear if i literally dont mess with any of the other GUI components....my sample code should help describe my anger...dont mind the shadow code, it was for testing purposes, which obviously didnt help.

//This method is called once a user presses the "first" login button on the main GUI
public synchronized void loginPopUpThread() {
    doHelloWorld = new Thread(){
        @Override
        public synchronized void run()
        {
            try
            {
                    loginPopUpFrame.pack();
                    loginPopUpFrame.setVisible(true);
                    System.out.println("waitin");
                    doHelloWorld.wait();
                    System.out.println("Not Sleepin..");
                    loginPopUpFrame.pack();
                    loginPopUpFrame.setVisible(false);
            }
            catch (InterruptedException e)
            {
            }
        }
    };
    doHelloWorld.start();

//This is called when the "second" loginB is pressed and the password is correct...
public synchronized void notifyPopUp() {
    synchronized(doHelloWorld) {

        doHelloWorld.notifyAll();
        System.out.println("Notified");
    }
}

I've also tried Swing Utilities but maybe i implemented it wrong as it's my first time using them. It essentially does the same thing as the code above except the window freezes when it gets to wait, which the above code doesnt do:

javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public synchronized void run() {
            try
            {
                    loginPopUpFrame.pack();
                    loginPopUpFrame.setVisible(true);
                    System.out.println("waitin");
                    wait();
                        System.out.println("Not Sleepin.");
                        loginPopUpFrame.pack();
                       loginPopUpFrame.setVisible(false);
            }
            catch (InterruptedException e)
            {
            }
        }
    });

PLEASE HELP ME!!!

Answer 1

The Swing components should only be manipulated by the swing event dispatch thread.

class SwingUtilites has methods to submit tasks to the dispatch thread.

Answer 2

It is difficult to diagnose your problem. I'm not sure what you're trying to do with the wait methods, but I recommend leaving wait/notify alone.

This code has two frames - when you create a second frame, the first is hidden until you close it.

public class SwapFrames {

  private JFrame frame;

  private JFrame createMainFrame() {
    JButton openOtherFrameButton = new JButton(
        "Show other frame");

    frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container contentPane = frame.getContentPane();
    contentPane.setLayout(new FlowLayout());
    contentPane.add(openOtherFrameButton);
    frame.pack();

    openOtherFrameButton
        .addActionListener(new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent e) {
            onClickOpenOtherFrame();
          }
        });

    return frame;
  }

  private void onClickOpenOtherFrame() {
    frame.setVisible(false);

    JFrame otherFrame = new JFrame();
    otherFrame
        .setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    otherFrame.setContentPane(new JLabel(
        "Close this to make other frame reappear."));
    otherFrame.pack();
    otherFrame.setVisible(true);
    otherFrame.addWindowListener(new WindowAdapter() {
      @Override
      public void windowClosed(WindowEvent e) {
        frame.setVisible(true);
      }
    });
  }

  public static void main(String[] args) {
    JFrame frame = new SwapFrames().createMainFrame();
    frame.setVisible(true);
  }

}

Because I don't see any evidence of them in your code, I'm going to suggest you read up on using event listeners rather than trying to "wait" for code to finish.

It isn't entirely clear what you're trying to achieve, but you might be better off with a modal dialog:

public class DialogDemo {

  public JFrame createApplicationFrame() {
    JButton openDialogButton = new JButton("Open Dialog");

    final JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container container = frame.getContentPane();
    container.setLayout(new FlowLayout());
    container.add(openDialogButton);
    frame.pack();

    openDialogButton
        .addActionListener(new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent e) {
            onOpenDialog(frame);
          }
        });

    return frame;
  }

  private void onOpenDialog(JFrame frame) {
    JDialog dialog = createDialog(frame);
    dialog.setVisible(true);
  }

  private JDialog createDialog(JFrame parent) {
    JButton closeDialogButton = new JButton("Close");

    boolean modal = true;
    final JDialog dialog = new JDialog(parent, modal);
    dialog
        .setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
    Container container = dialog.getContentPane();
    container.add(closeDialogButton);
    dialog.pack();
    dialog.setLocationRelativeTo(parent);

    closeDialogButton
        .addActionListener(new ActionListener() {
          @Override
          public void actionPerformed(ActionEvent e) {
            dialog.setVisible(false);
          }
        });

    return dialog;
  }

  public static void main(String[] args) {
    new DialogDemo().createApplicationFrame().setVisible(
        true);
  }

}

Answer 3

Rules of thumb:

• Don't manipulate GUI components in arbitrary threads; always arrange to manipulate them in the event thread
• Never wait or sleep inside the event thread (so, never inside code sent to invokeLater())

So the answer to how you solve this problem is "some other way"...

Standing back from the problem a bit, what is it you're actually trying to do? If you just want a login dialog to wait for the user to enter user name and password, is there a reason not to just use a modal JDialog (after all, that's what it's there for...).

If you really do want some arbitrary thread to wait for a signal to close the window/manipulate the GUI, then you need to do the waiting in the other thread, and then make that thread call SwingUtilities.invokeLater() with the actual GUI manipulation code.

P.S. There are actually some GUI manipulation methods that it is safe to call from other threads, e.g. calls that are "just setting a label" are often safe. But which calls are safe isn't terribly well-defined, so it's best just to avoid the issue in practice.

Answer 4

How about doing simply:

//This method is called once a user presses the "first" login button on the main GUI
public void loginPopUpThread() {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            loginPopUpFrame.pack();
            loginPopUpFrame.setVisible(true);
        }
    };
}

//This is called when the "second" loginB is pressed and the password is correct...
public void notifyPopUp() {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            loginPopUpFrame.setVisible(false);
        }
    };
}

Answer 5

What you really want to be using is a modal JDialog.

Note, bits of this are left out. It's your homework/project.

public void actionPerformed(ActionEvent e)
{
   // User clicked the login button
   SwingUtilities.invokeLater(new Runnable()
   {
       public void run()
       {
         LoginDialog ld = new LoginDialog();
         // Will block
         ld.setVisible(true);
       }
   });
}

public class LoginDialog extends JDialog
{
    public LoginDialog()
    {
        super((Frame)null, "Login Dialog", true);

        // create buttons/labels/components, add listeners, etc
    }

    public void actionPerformed(ActionEvent e)
    {
       // user probably clicked login
       // valid their info
       if(validUser)
       {
          // This will release the modality of the JDialog and free up the rest of the app
          setVisible(false);
          dispose();
       }
       else
       {
          // bad user ! scold them angrily, a frowny face will do
       }
    }
}