Swing change JScrollPane content

Question

Hi I am trying to change JScrollPane content like

scrollPanel = new JScrollPane(new Welcome().display());

        for(final JMenuItem i : items) {
            i.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    String txt = i.getText();

                    if(txt.equals("Open")) {
                        scrollPanel = new JScrollPane(new Open().display());
                    } else if(txt.equals("Save")) {
                        scrollPanel = new JScrollPane(new Save().display());
                    } else if(txt.equals("Save as")) {
                        scrollPanel = new JScrollPane(new SaveAs().display());
                    } else if(txt.equals("Close")) {
                        new Close().ask();
                        scrollPanel = new JScrollPane();
                    }

                    scrollPanel.revalidate();
                    scrollPanel.repaint();
                }
            });
        }   

        scrollPanel.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPanel.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);

        menuBar.add(menu);
        frame.setJMenuBar(menuBar);
        frame.add(scrollPanel);

        frame.pack();
        frame.setSize(640, 480);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);

But its not working. Each class Open, Save, SaveAs return JPane with JLabel inside. Ex.

public class Open {
    public JPanel display() {
        JPanel panel = new JPanel();
        panel.add(new JLabel("Open"));
        return panel;
    }
}

Answer 1

You're not changing the scrollpane content. You're assigning a new JScrollPane instance to the scrollPanel field. The scroll pane you have added to the frame and which is displayed stays exactly as it is.

If you want to change the scroll pane contents, you should use

scrollPanel.setViewportView(new Open().display());