Question

BorderLayout does something strange. If I add two panels to a Container with the same constraint (BorderLayout.CENTER for instance), then the first one goes away, even if the second one is deleted or made invisible

It seems as though it would make sense for it to “stack” each element on top of the previous ones.

Is this correct and by design? If so, is there some documentation on it?

Has anyone else been frustrated by it? Have you a solution, such as a custom LayoutManager?

Sample code:

JFrame frame = new JFrame();
frame.setSize(500, 500);

JPanel panel1 = new JPanel();
panel1.setBackground(Color.blue);
frame.getContentPane().add(panel1);

JPanel panel2 = new JPanel();
panel2.setBackground(Color.red);
frame.getContentPane().add(panel2);

panel2.setVisible(false); // Seems like it should allow us to see panel1.

frame.setVisible(true);

This creates and displays a 500×500 blank box.

Answer 1

BorderLayout was simply not designed to do what you want. Separation of responsibility. If you want that behavior you should compose: combine the BorderLayout with a CardLayout. Though for the actual stack behavior, you’ll have to code something yourself (or find someone who already has.)