Java cardLayout wrong parent

Question

I know this question has been asked before but i cant seem to make the answers work, nor understand them.

What i am trying to do is to swap panels which button click. This is the my main function:

public class CreateWindow extends JFrame{

    public CreateWindow() {
        this.setTitle("Test GUI");

        this.putIcon();
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(512, 512);

        this.add(new CreatePanel());

        this.setVisible(true);
    }

and this is where i try to create the panels:

public class CreatePanel extends JPanel implements ActionListener {

    JTextArea directoryText;
    JFileChooser chooser;
    String directory;
    ArrayList<File> files;
    CardLayout cards;
    JPanel panel1, panel2;

    public CreatePanel() {
        this.setSize(256, 256);
        cards = new CardLayout();
        this.setLayout(cards);

        files = new ArrayList<>();
        panel1 = new JPanel(null);
        panel2 = new JPanel(null);

        this.add(panel1, "panel1");
        this.add(panel2, "panel2");
        panel1.setBackground(Color.red);
    panel2.setBackground(Color.blue);

        cards.show(panel1, "panel1");

    }
}

And i keep on getting the following error:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: wrong parent for CardLayout
    at java.awt.CardLayout.checkLayout(CardLayout.java:404)
    at java.awt.CardLayout.show(CardLayout.java:526)
    at jeasussaves.CreatePanel.<init>(CreatePanel.java:54)
    at jeasussaves.CreateWindow.<init>(CreateWindow.java:29)
    at jeasussaves.JeasusSaves$1.run(JeasusSaves.java:22)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:749)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:702)
    at java.awt.EventQueue$3.run(EventQueue.java:696)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:719)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Answer 1

CardLayout#show(Container, String) requires you to specify the "deck" you want to use as the first parameter, then a "card" from that deck as the second parameter.

In this case, your JPanel (the one being extended) is the deck (since it's the one using CardLayout ) and panel1 is a card, since you added it to the deck. Change your cards.show(panel1, "panel1") to cards.show(this, "panel1") .

There's no need to display your first card after adding all the cards. The first card you add is the first card to be displayed