Setting the value of a JScrollBar inside a JScrollPane not working.

Question

I have a display area (JPanel) inside a JScrollPane. What i want to do is that every time the user closes my application a file is saved with some preferences, like position and size onscreen, and the values of the scrollbars. My problem is that when I try to set the values of the JScrollBars, they seem to be completely ignored.
I made a small class to illustrate this:
import java.awt.*;
import javax.swing.*;
public class ScrollExample extends JFrame
     private JPanel display;
     private JScrollPane displayScroll;
     public ScrollExample()
          display = new JPanel();
          display.setPreferredSize( new Dimension( 800, 600 ) );
          displayScroll = new JScrollPane( display );
          add( displayScroll );
          setSize( 400, 300 );
          setVisible( true );
          displayScroll.getHorizontalScrollBar().setValue( displayScroll.getHorizontalScrollBar().getMaximum() );
     public static void main( String args[] )
          new ScrollExample();
}The behaviour of is as intended. However if we switch the two lines to be:
displayScroll.getHorizontalScrollBar().setValue( displayScroll.getHorizontalScrollBar().getMaximum() );
setVisible( true );and launch it, the scrollbar appears to have moved only a small amount. This leads me to believe that it has something to do with the main window being visible. In my actual application, this call to setValue is ignored, unlike in this sample one. Even placing it after the setVisible call, it does not do anything.
When I tried to use:
     Runnable doScroll = new Runnable()
             public void run()
                  taskDisplayScroll.getHorizontalScrollBar().setValue( 200 );
         SwingUtilities.invokeLater(doScroll);after the setVisible call, as mentioned on http://forum.java.sun.com/thread.jspa?threadID=723424, it rarely (maybe 3 out of 20 times) sets the scrollbar to the indicated value.
My question is this: What does the setValue() call depend on to run properly, and how do I code it to work in my program?
If you need any additional information, please ask.
Note: In the sample class I provided, the scrollbar moves to its proper spot, I could not cause it to not move at all, as is the case in my application that seems to have the same calls.
Thanks, Serge.
Edited by: super_serge on Jun 26, 2008 8:23 AM

Answer 1

Can you please explain to me how b) would be implemented.Read the Swing tutorial on Concurrency for the new approach in JDK1.6, or I still prefer to use SwingUtilities.invokeLater for somthing simple like this.