Panels and panels

[Anna Hays]

Hi, I am wondering if having too many panels to make the desire look on the front end is bad? I know nested HTML table is bad, what about nesting panels in Swing? I have left my assignment for another few months now avoiding Swing. Does anybody know some good links on good practices on Swing? Not just how to use it.

Huge thanks!!

*Swingphobia*

[Robert Konigsberg]

Nested panels are a good thing. To some degree you are expected to leverage nested panels for complex GUIs. But more importantly, if you're clever you can separate functionality, or easily reuse a nested panel, either by using methods or extended classes:

Here's a contrived example:

 
interface OkCancelListener
{
    public void okButtonPressed();
    public void cancelButtonPressed();
}
 
class OkCancelPanel extends JFrame
{
    public JPanel createOkCancelPanel(String okText, String cancelText, OkCancelListener listener)
    {
        JPanel panel = new JPanel(new BorderLayout());
        JButton okButton = new JButton(okText);
        panel.add(okButton, BorderLayout.WEST);
        JButton cancelButton = new JButton(cancelText);
        panel.add(cancelButton, BorderLayout.WEST);
        okButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent event)
            {
                listener.okButtonPressed();
            }
        });
        cancelButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent event)
            {
                listener.cancelButtonPressed();
            }
        });
    }
}

Now this application (at least, mine) isn't really that big to warrant something like that, BUT, it is useful to have something like this:

class MyDialog extends JDialog
{
    public MyDialog()
    {
        contentPane.setLayout(new BorderLayout());
        contentPane.add(createMainPanel(), BorderLayout.CENTER);
        contentPane.add(createOkCancelPanel(), BorderLayout.SOUTH);
    }
    private JPanel createOkCancelPanel {...}
    private JPanel createMainPanel()
    {
        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        panel.add(createHeaderPanel(), BorderLayout.NORTH);
        panel.add(createLeftPanel() BorderLayout.CENTER);
        panel.add(createRightPanel(), BorderLayout.EAST);
    }
    private JPanel createHeaderPanel{...}
    private JPanel createLeftPanel{...}
    private JPanel createRightPanel{...}
}

That and some good documentation should (once again, I suspect) get you points for code clarity.