I have a JList created with a DefaultListModel and a custom cell renderer.
After several tries I have got this to work up until I update the list
model.  As soon as I do, no matter how I do it, the entire JList goes blank,
including the enclosing JScrollPane, despite the fact that my custom cell
renderer is invoked to paint the cells.

Note that this is in JDK 1.4.2.

The cell renderer looks like:

public class LayoutColumnRenderer extends Component
  implements ListCellRenderer
{
   public LayoutColumnRenderer(JList list)
   {
...
   }  // LayoutColumnRenderer.LayoutColumnRenderer

   public Component getListCellRendererComponent(
    JList list,
    Object value,
    int index,
    boolean isSelected,
    boolean hasFocus) {
...
return this;
   }  // LayoutColumnRenderer.getListCellRendererComponent

  public void paint(Graphics g)  {
    g.setColor(getBackground());
    g.fillRect(0,0,getWidth(),getHeight());
    g.setColor(getForeground());
    g.drawString(text, 0, fm.getAscent());
   }  // LayoutColumnRenderer.paint

}  // class LayoutColumnRenderer

The JList is created as follows:

   private Vector selectedFlds;
   private JList selectedList;
   private DefaultListModel selectedListModel;
...
    selectedListModel = new DefaultListModel();
    selectedListModel.ensureCapacity(selectedFlds.size());
    Iterator  iter = selectedFlds.iterator();
    while(iter.hasNext())
    {
       selectedListModel.addElement(iter.next());
    }
    selectedList = new JList(selectedListModel);
    selectedList.setVisibleRowCount(10);// show 10 rows at a time
    selectedList.clearSelection(); // nothing selected for action
    selectedList.setCellRenderer(new LayoutColumnRenderer(selectedList) );
    selectedSp = new JScrollPane(selectedList);
...
The list is updated as follows.  LayoutColumn is the class of elements that
appear in the selectedFlds Vector.

    LayoutColumn lc;
    lc = new LayoutColumn(field, this, log);
    try {
       selectedListModel.add(after, lc);
    }
    catch (ArrayIndexOutOfBoundsException obe)
    {
...
    }
    selectedFlds.insertElementAt(lc, after++);
...

As a result of calling DefaultListModel.insertElementAt
LayoutColumnRenderer.paint is called ONCE FOR EVERY ELEMENT IN THE UPDATED
ListModel.  That is it is not called only for those elements of the list
that are currently visible through the window of the scroll pane, as it was
when the JList was first displayed, and as it is each time I scroll through
the JList.  It is called even for those elements that are not currently
visible.  And yet, despite that excessive processing, none of the cells are
repainted on the screen, and even the scroll bar elements disappear.  Based
upon the calls to my paint method I can see that the ListModel was correctly
updated, it just doesn't display properly.

This does not happen if LayoutColumnRenderer is derived from JLabel, so I
suspect that I am hitting some obscure interaction with JScrollPane that
JLabel knows all about, but which is obscured by the coding style of Swing
components.  I cannot use JLabel because the output painting is actually a
bit more complicated than what I show above, so I cannot leave the default
paint function of JLabel.

Any ideas?  There may be a bug in JList that it calls my paint method too
many times after the ListModel is updated, but aside from that why does
nothing appear when my paint method is called?