JTextPane inside JScrollPane resizing when updated

Question

Hiya all,
I've been struggling with this problem and checking the forums, but didn't find a solution, so I hope someone can help...at least help me for the nice picture :) It has to do with JTextPane's automatically resizing to their content on a GUI update, rather than scrollbars appearing (the desired result).
Basically, I have a scenario where I am creating a series of multiple choice answers for a question. Each answer consists of a JTextPane inside a JScrollPane, and a JRadioButton, which are all contained in a JPanel (called singleAnswerPanel). So for 2 answers, I would have 2 of these singleAnswerPanels. There is a one large JPanel that contains all the singleAnswerPanels (called allAnswersPanel). This allAnswersPanel is contained in a JScrollPane. Graphically, this looks like:
   |       JPanel (allAnswersPanel) inside a JScrollPane            |
   |                                                                |
   |  ------------------------------------------------------------  |
   | |     JPanel (singleAnswerPanel)                             | |
   | |    ----------------------------------                      | |
   | |   |  JTextPane inside a JScrollPane  |     * JRadioButton  | |
   | |    ----------------------------------                      | |
   | |                                                            | |
   |  ------------------------------------------------------------  |
   |                                                                |
   |                                                                |
   |  ------------------------------------------------------------  |
   | |     JPanel (singleAnswerPanel)                             | |
   | |    ----------------------------------                      | |
   | |   |  JTextPane inside a JScrollPane  |     * JRadioButton  | |
   | |    ----------------------------------                      | |
   | |                                                            | |
   |  ------------------------------------------------------------  |
   |                                                                |
    ----------------------------------------------------------------So above, I show 2 answers that can be filled in with text. So assuming both answer JTextPanes are filled with text beyond their current border (scrollbars appear as expected) and the user wishes to add more answers. I have a button to add another singleAnswerPanel to the containing JPanel (allAnswersPanel), and then I validate the main JScrollPane that contains the allAnswersPanel as it's view. The problem that occurs is the existing single answer JTextPanes resize to the size of their text and the vertical scrollbars (only vertical ones setup) of the JTextPanes dissappear! My intent is to keep the existing JScrollPanes the same size (with their scrollbars) when a new answer is added.
The code snippet below shows what gets done when a new answer is added:
private void createAnswer()
    // The panel that will hold the new single answer JTextPane pane
    // (inside a JScrollPane) and radio button.
    JPanel singleAnswerPanel = new JPanel();
    // Create the text pane for the single answer.
    JTextPane singleAnswerTextPane = new JTextPane();
    Dimension dimensions = new Dimension(200, 30);
    singleAnswerTextPane.setPreferredSize(dimensions);
    singleAnswerTextPane.setMaximumSize(dimensions);
    // Create a scroll pane and add the single answer text pane.
    JScrollPane singleAnswerScrollPane =
     new JScrollPane(singleAnswerTextPane);
    // Create a radio button that is associated with the single
    // answer text pane above.
    JRadioButton singleAnswerRadioButton = new JRadioButton();
    // Add the scroll pane and radio button to the panel (for a single
    // answer).
    singleAnswerPanel.add(singleAnswerScrollPane);
    singleAnswerPanel.add(singleAnswerRadioButton);
    // Add the panel holding a single answer to the panel holding
    // all the answers.
    m_allAnswersPanel.add(singleAnswerPanel);
    // Update the display.  m_allAnswersScrollPane is a JScrollPane
    // that has the m_allAnswersPanel (JPanel) as its view.
    m_allAnswersScrollPane.validate();
}     Sorry for the length of the message, but I really want to solve this problem. So again, when updating the JScrollPane with validate(), the JTextPane for a single answer resizes to it's contents (plain text currently) and loses it's vertical scrollbars, but I want it to stay the same size and maintain the scrollbars.
Thanks!

Answer 1

http://java.sun.com/docs/books/tutorial/uiswing/mini/layout.htmlimport javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
public class Test extends JFrame {
    int cnt=0;
    Random r = new Random();
    String[] nouns = {"air","water","men","idjits"};
    JPanel mainPanel = new JPanel(new GridBagLayout());
    JScrollPane mainScroll = new JScrollPane(mainPanel);
    JScrollBar mainScrollBar = mainScroll.getVerticalScrollBar();
    public Test() {
     setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
     Container content = getContentPane();
     content.add(new JLabel("QuizMaster 2003"), BorderLayout.NORTH);
     content.add(mainScroll, BorderLayout.CENTER);
     JButton jb = new JButton("New");
     content.add(jb, BorderLayout.SOUTH);
     jb.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
          JPanel questionPanel = new JPanel(new GridBagLayout());
          questionPanel.add(new JLabel("Question "+cnt++),
               new GridBagConstraints(0,0,1,1,0.0,0.0,
                    GridBagConstraints.EAST, GridBagConstraints.NONE,
                    new Insets(1,2,1,2),0,0));
          questionPanel.add(new JLabel("Why is there "+
                        nouns[r.nextInt(nouns.length)]+"?"),
               new GridBagConstraints(1,0,1,1,0.0,0.0,
                    GridBagConstraints.EAST, GridBagConstraints.NONE,
                    new Insets(1,2,1,2),0,0));
          JTextArea jta = new JTextArea();
          JScrollPane jsp = new JScrollPane(jta);
          jsp.setPreferredSize(new Dimension(300,50));
          questionPanel.add(jsp, new GridBagConstraints(0,1,2,1,0.0,0.0,
                    GridBagConstraints.EAST, GridBagConstraints.BOTH,
                    new Insets(1,2,1,2),0,0));
          mainPanel.add(questionPanel, new GridBagConstraints(0,cnt,1,1,0.0,0.0,
                        GridBagConstraints.EAST,GridBagConstraints.NONE,
                        new Insets(0,0,0,0),0,0));
          mainPanel.revalidate();
          mainScroll.getViewport().setViewPosition(new Point(0, mainPanel.getHeight()));
     setSize(400,300);
     show();
    public static void main( String args[] ) { new Test(); }
}