Understanding CardLayout and panel visibility

Question

Consider the following:

    JFrame frame = new JFrame();
    frame.setLayout(new CardLayout());

    JPanel panel1 = new JPanel();
    panel1.setPreferredSize(new Dimension(1000, 1000));
    panel1.setBackground(Color.RED);

    JPanel panel2 = new JPanel();
    panel2.setPreferredSize(new Dimension(100, 100));
    panel2.setBackground(Color.GREEN);

    frame.add(panel1);
    frame.add(panel2);

    frame.pack();
    frame.setVisible(true);

No matter what, the frame ends up being 1000x1000. It's my understanding that using the card layout, only one panel will be shown at a time - hence if that panel is the 100x100, the frame should also be 100x100? But this is not the case. Even when the frame is green (ie it's panel 2 being displayed), the frame is still 1000x1000.

In fact, even adding the line panel1.setVisiblity(false); changes nothing; it still affects the frame size, making it 1000x1000!

I'm clearly misunderstanding how the card layout and frame sizing works. Can someone clear up my confusion?

Answer 1

It's my understanding that using the card layout, only one panel will be shown at a time - hence if that panel is the 100x100, the frame should also be 100x100?

No. A CardLayout will take the preferred size of the widest and tallest components within it.