Updating a JScrollPane

Question

Hi, I've a big problem with a JScrollPane. I have a JScrollPane and in it there is a JPanel with a BorderLayout divided in NORTH and CENTER. In the NORHT and CENTER there are other two JPanel. The problem is that I need to add buttons and label to the center panel but when I add these they do not appear. I tried with validate() and repaint() method for the Center JPanel and then use setVieportView but it does not function.
Do someone had these problems with JScrollPane? Here is an example of code just to show what I mean. This is not the code I use, I do not post it cause it too long:
JPanel centerPanel = new JPanel();
     JScrollPane relationsScrollPane = new JScrollPane();
     public JScrollPane getRelationsSP(){
               relationsScrollPane.setAutoscrolls(true);
               relationsScrollPane .setViewportView(getCenterPanel());          
               return relationsScrollPane ;
     public JPanel getCenterPanel() {
          return centerPanel;
public void addDelComponentRelazioni (){     
          centerPanel.removeAll();
          centerPanel.add(add());
          centerPanel.validate();
          centerPanel.repaint();
          relationsScrollPane.invalidate();
          relationsScrollPane.validate();
          relationsScrollPane.repaint();
          relationsScrollPane .setViewportView(centerPanel);                    
     public Box add() {
          Box boxRelations = Box.createVerticalBox();
          JPanel pannello1 = new JPanel();
          JPanel pannello2 = new JPanel(new FlowLayout(FlowLayout.CENTER));
          pannello1.setLayout(new FlowLayout(FlowLayout.LEFT));
          JLabel labelRelazioni = new JLabel("Relations: ");
          pannello1.add(labelRelazioni);
          boxRelations.add(pannello2);
          return boxRelations;
     I dunno why what I add is not shown although if I use the method centerPanel.getComponentCount() and do not use removeAll(), the number of component increases but they are not shown. I hope someone can help me.

Answer 1

well, the code of add() is
public Box add() {
          Box boxRelations = Box.createVerticalBox();
          JPanel pannello1 = new JPanel();
          pannello1.setLayout(new FlowLayout(FlowLayout.LEFT));
          JLabel labelRelazioni = new JLabel("Relations: ");
          pannello1.add(labelRelazioni);
          boxRelations.add(pannello1);
          return boxRelations;
     }