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JScrollPane failed to update scrollbar

Posted on 2004-10-25
Medium Priority
Last Modified: 2008-03-17

I want to allow the user to enlarge the font of a JTextArea inside JScrollPane.
For some unknown reasons, the JScrollPane would not update at all
after I call jtextArea.setFont() with larger font size.
For example:
(1) The scrollbar would not show up.
(2) The enlarged jtextArea would not be visible at the end.

I have to manually resize the window to force JScrollPane
to redraw and update scrollbar.

I tried revalidate() and repaint(), but without success.
Is this a bug in JScrollPane ?
If yes, how do I go around this problem ?

Please advise.

PS. Here is my sample test code, tested under JDK 1.3.0. on Windows 2K.

package test;

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class Panel6 extends JPanel {
  BorderLayout borderLayout1 = new BorderLayout();
  JButton jButton1 = new JButton();
  JTextArea textArea = new JTextArea();
  JScrollPane scrollPanel = new JScrollPane();

  public Panel6() {

    // button to change font
    jButton1.setText("Change Font");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {

    this.add(jButton1, BorderLayout.NORTH);
    scrollPanel.getViewport().add(textArea, null);
    this.add(scrollPanel, BorderLayout.CENTER);

    // these 2 line  below somehow cause JScrollpane to fail to update.
    // if remove, JScrollpane gets updated. why ???

  // fill in multiline text
  void fillText() {
   String text="";
   for (int i = 0; i < 40; i++) {
     text +=" ABC"+i;

  // update font style and size
  void jButton1_actionPerformed(ActionEvent e) {
    Font font1 = textArea.getFont();
    Font font2 = new Font(font1.getName(), Font.BOLD , 22 );
    // textArea.revalidate(); // this does NOT help
    // scrollPanel.getParent().repaint(); // this does NOT help

  //***** self test ********
  public static void main(String[] args) {
    // create test panel
    Panel6 t = new Panel6();
    // display panel in a frame
    JFrame frame = new JFrame();

Question by:csunlistek
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LVL 92

Accepted Solution

objects earned 1500 total points
ID: 12407708
works fine here (using 1.4).
try updating your java runtime.

Expert Comment

ID: 12407818
I've also checked ur code its working fine using jdk1.4. You need to updated ur JDK.
or try to add
 line after
// scrollPanel.getParent().repaint(); // this does NOT help

Naeem Shehzad Ghuman

Author Comment

ID: 12408290
If it works in JDK 1.4 but not JDK 1.3, then I guess it is indeed a bug.

Unfortunately, I need to stay with JDK 1.3 for now.
I try this.updateUI() as Naeemg suggested but it does not work in JDK 1.3.

Any suggestion on how I can get this to work in JDK 1.3.0 ?

I guess I need to somehow notify JScrollPane about the new size and force a repaint.

Thanks for any comments.

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LVL 92

Expert Comment

ID: 12408307
> I guess I need to somehow notify JScrollPane about the new size and force a repaint.

try calling revalidate() on the scroll panes parent.

Author Comment

ID: 12408427
I added this.revalidate() after the line
 // scrollPanel.getParent().repaint(); // this does NOT help

but it does not work in JDK 1.3.

LVL 86

Expert Comment

ID: 12409693
Try creating your components thus:

JTextArea textArea = new JTextArea();
 JScrollPane scrollPanel = new JScrollPane(textArea);

Author Comment

ID: 12412751
I tried the fix as  CEHJ suggested above
but it does NOT work.

Author Comment

ID: 12413122
OK. I have enough of this JDK 1.3 bug.
I am upgrading to JDK 1.4 so I can move forward.
Thanks for all the comments.
LVL 92

Expert Comment

ID: 12416383

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