🚀 go-pugleaf

On Thu, 11 May 2000 13:33:19 -0500, Joe Dorman wrote:

> Here's a sample of my attempt to subclass ScrollPaneLayout.
> I can't get it to work.  If I comment out the setLayout call,
> the JTextArea displays the text.  With the setLayout call,
> nothing displays in the JScrollPane.  Any ideas???

I found the problem.  The following is from the JavaDocs for the class 
ScrollPaneLayout:

   public void syncWithScrollPane(JScrollPane sp)

      This method must be called after setting a JScrollPanes
      layout manager. It initializes all of the internal fields
      that are ordinarily set by addLayoutComponent().

      For example:

         ScrollPaneLayout mySPLayout = new ScrollPanelLayout() {
            public void layoutContainer(Container p) {
               super.layoutContainer(p);
               // do some extra work here ...
            }
         };
         scrollpane.setLayout(mySPLayout):
         mySPLayout.syncWithScrollPane(scrollpane);

This is, IMHO, a very bad design.  Since JScrollPane requires that any 
LayoutManager set on it be a subclass of ScrollPaneLayout, it could and 
should call syncWithScrollPane() itself.

I can think of no reason to impose this requirement on the caller.  It 
just invites errors.

-- 
John P. McGrath
<JPMcGrath@fast.net>
<jpm@nscs.fast.net>