Can't use BoxLayout more than once in a class?

Question

I have a JPanel inside of a JPanel. I am using a BoxLayout
manager on the main JPanel, and I used to use a GridLayout on the
sub JPanel. Yesterday I changed the Layout Manager of the subPanel
to BoxLayout, and now I get this strange error at runtime. Why can't I use
2 Box Layouts? Why is Java trying to share them?
Exception in thread "main" java.awt.AWTError: BoxLayout can't be shared
        at javax.swing.BoxLayout.checkContainer(BoxLayout.java:408)
        at javax.swing.BoxLayout.invalidateLayout(BoxLayout.java:195)
        at java.awt.Container.invalidate(Container.java:851)
        at java.awt.Component.addNotify(Component.java:5398)
        at java.awt.Container.addNotify(Container.java:1852)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at java.awt.Container.addNotify(Container.java:1859)
        at javax.swing.JComponent.addNotify(JComponent.java:4270)
        at javax.swing.JRootPane.addNotify(JRootPane.java:658)
        at java.awt.Container.addNotify(Container.java:1859)
        at java.awt.Window.addNotify(Window.java:395)
        at java.awt.Frame.addNotify(Frame.java:479)
        at java.awt.Window.pack(Window.java:413)
        at CDBTest.main(CDBTest.java:246)I need help.
Thanks
Josh

Answer 1

hmm, the following's my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class PreferencesPane extends JPanel {
//Main pane to be added to the class
private JTabbedPane mainPane;
//the options pane
private JPanel optionsPane;
//the accounts list
private JPanel accountsPane;
//the personal information display
private JPanel perInfoPane1;
private JPanel perInfoPane2;
//labels
private JLabel usernameLabel;
private JLabel newPassLabel;
private JLabel confPassLabel;
private JPanel separatorLabel;
private JLabel nameLabel;
private JLabel emailLabel;
private JLabel titleLabel;
private JLabel companyLabel;
private JLabel homePhoneLabel;
private JLabel workPhoneLabel;
private JLabel cellPhoneLabel;
private JLabel faxLabel;
private JLabel homeAddLabel;
private JLabel workAddLabel;
private JLabel notesLabel;
//Textfields
private JTextField usernameField;
private JPasswordField newPassField;
private JPasswordField confPassField;
private JPanel separatorField;
private JTextField nameField;
private JTextField emailField;
private JTextField titleField;
private JTextField companyField;
private JTextField homePhoneField;
private JTextField workPhoneField;
private JTextField cellPhoneField;
private JTextField faxField;
private JTextArea homeAddField;
private JTextArea workAddField;
private JTextArea notesField;
//Save information button
private JButton saveInfoButton;
private JPanel perInfoPane;
public PreferencesPane() {
optionsPane = new JPanel();
accountsPane = new JPanel();
//labels
usernameLabel = new JLabel("Username:");
newPassLabel = new JLabel("New Password:");
confPassLabel = new JLabel("Confirm New Password:");
separatorLabel = new JPanel();
nameLabel = new JLabel("Name:");
emailLabel = new JLabel("Email:");
titleLabel = new JLabel("Title:");
companyLabel = new JLabel("Company:");
homePhoneLabel = new JLabel("Home Phone:");
workPhoneLabel = new JLabel("Work Phone:");
cellPhoneLabel = new JLabel("Cell Phone:");
faxLabel = new JLabel("Fax:");
homeAddLabel = new JLabel("Home Address:");
workAddLabel = new JLabel("Work Address:");
notesLabel = new JLabel("Notes:");
//Textfields
usernameField = new JTextField(20);
newPassField = new JPasswordField(20);
confPassField = new JPasswordField(20);
separatorField = new JPanel();
nameField = new JTextField(20);
emailField = new JTextField(20);
titleField = new JTextField(20);
companyField = new JTextField(20);
homePhoneField = new JTextField(20);
workPhoneField = new JTextField(20);
cellPhoneField = new JTextField(20);
faxField = new JTextField(20);
homeAddField = new JTextArea(10,20);
workAddField = new JTextArea(10,20);
notesField = new JTextArea(10,20);
//Panel to contain the textfield and labels
perInfoPane1 = new JPanel(new GridLayout(12,2));
perInfoPane1.add(usernameLabel);
perInfoPane1.add(usernameField);
perInfoPane1.add(newPassLabel);
perInfoPane1.add(newPassField);
perInfoPane1.add(confPassLabel);
perInfoPane1.add(confPassField);
perInfoPane1.add(separatorLabel);
perInfoPane1.add(separatorField);
perInfoPane1.add(nameLabel);
perInfoPane1.add(nameField);
perInfoPane1.add(emailLabel);
perInfoPane1.add(emailField);
perInfoPane1.add(titleLabel);
perInfoPane1.add(titleField);
perInfoPane1.add(companyLabel);
perInfoPane1.add(companyField);
perInfoPane1.add(homePhoneLabel);
perInfoPane1.add(homePhoneField);
perInfoPane1.add(workPhoneLabel);
perInfoPane1.add(workPhoneField);
perInfoPane1.add(cellPhoneLabel);
perInfoPane1.add(cellPhoneField);
perInfoPane1.add(faxLabel);
perInfoPane1.add(faxField);
perInfoPane2 = new JPanel(new GridLayout(3,2));
perInfoPane2.add(homeAddLabel);
perInfoPane2.add(homeAddField);
perInfoPane2.add(workAddLabel);
perInfoPane2.add(workAddField);
perInfoPane2.add(notesLabel);
perInfoPane2.add(notesField);
//save button
saveInfoButton = new JButton("Save information");
perInfoPane = new JPanel(new BoxLayout(perInfoPane,BoxLayout.Y_AXIS));
perInfoPane1.setAlignmentX(Component.LEFT_ALIGNMENT);
perInfoPane2.setAlignmentX(Component.LEFT_ALIGNMENT);
saveInfoButton.setAlignmentX(Component.LEFT_ALIGNMENT);
perInfoPane.add(perInfoPane1);
perInfoPane.add(perInfoPane2);
perInfoPane.add(saveInfoButton);
//adds components to the TabbedPane
mainPane = new JTabbedPane(JTabbedPane.LEFT);
mainPane.add("Options",optionsPane);
mainPane.add("Accounts",accountsPane);
mainPane.add("Personal Information",perInfoPane);
setLayout(new BorderLayout());
add(mainPane,BorderLayout.CENTER);
As you can see, the only time I use BoxLayout is the following line:
perInfoPane = new JPanel(new BoxLayout(perInfoPane,BoxLayout.Y_AXIS));
As far as I can tell, that's correct, but I'm still getting this at runtime:
Exception in thread "main" java.awt.AWTError: BoxLayout can't be shared
Anyone have any ideas?