Scrolling down automatically

Question

Hi
I noticed some strange behaviour of a JTextArea in a JScrollPane (I always use this like that, perhaps there might be better ways - I appreciate any suggestions on that, too). When I init the text area with "" the display always scrolls down to the new text when I append more.
But when I init the text area with some longer text the display won't scroll down anymore automatically - how can I fix that. I'd like it always to scroll the display down and to show the fresh text/last lines.
I wrote a demo to demonstrate the problem:
package scollbar;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.WindowConstants;
public class NewJFrame extends javax.swing.JFrame {
     private JScrollPane jScrollPane1;
     private JButton jButton1;
     private JTextArea jTextArea1;
     * Auto-generated main method to display this JFrame
     public static void main(String[] args) {
          NewJFrame inst = new NewJFrame();
          inst.setVisible(true);
     public NewJFrame() {
          super();
          initGUI();
     private void initGUI() {
          try {
               GridBagLayout thisLayout = new GridBagLayout();
               thisLayout.rowWeights = new double[] {0.1,0.0,0.1};
               thisLayout.rowHeights = new int[] {7,7,7};
               thisLayout.columnWeights = new double[] {0.1};
               thisLayout.columnWidths = new int[] {7};
               getContentPane().setLayout(thisLayout);
               setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
                    jScrollPane1 = new JScrollPane();
                    getContentPane().add(jScrollPane1, new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0, GridBagConstraints.CENTER, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0));
                    jScrollPane1.setPreferredSize(new java.awt.Dimension(300, 100));
                         jTextArea1 = new JTextArea();
                         jScrollPane1.setViewportView(jTextArea1);
//                          leaving it like this - it always scrolls down to the new text automatically
                         jTextArea1.setText("");
//                          BUT uncommenting this the display won't scroll down anymore automatically - why?!
//                         jTextArea1.append( "Your\n mouth\n keeps\n moving...\n but\n all\n I\n hear\n is\n blah!\n blah!\n blah!\n");
                    jButton1 = new JButton();
                    getContentPane().add(jButton1, new GridBagConstraints(0, 2, 1, 1, 0.0, 0.0, GridBagConstraints.NORTH, GridBagConstraints.NONE, new Insets(0, 0, 0, 0), 0, 0));
                    jButton1.setText("click");
                    jButton1.addActionListener( new ActionListener(){
                         public void actionPerformed( ActionEvent ae){
                              jTextArea1.append( "Your\n mouth\n keeps\n moving...\n but\n all\n I\n hear\n is\n blah!\n blah!\n blah!\n");
               pack();
               setSize(400, 300);
          } catch (Exception e) {
               e.printStackTrace();
}

Answer 1

When I init the text area with "" the display always scrolls down to the new text when I append more.
But when I init the text area with some longer text the display won't scroll down anymore automatically Read my reply in this posting for an explanation on what is happening:
http://forum.java.sun.com/thread.jspa?forumID=57&threadID=638441