Java: CardLayout switching between cards

Question

I've got class 'Frame' which extends `JFrame` and separetad `JPanels`: `MainMenu` and `SinglePanel` I am using `CardLayout`, but I've got problem when switching back to panels using `buttonSingle` and `powrot` buttons. So my question is how can I change/swap between cards using these buttons? My `Frame` class: ``` public class Frame extends JFrame{ CardLayout cl = new CardLayout(); final MainMenu menuPanel = new MainMenu(); final SinglePanel singlePanel = new SinglePanel(); public Frame(){ setLayout(cl); add(menuPanel,"menu"); add(singlePanel,"single"); setSize(200, 200); setLocationRelativeTo(null); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); setVisible(true); setEnabled(true); swapView("menu"); } public void swapView(String view){ cl.show(getContentPane(),view); } } ``` my `MainMenu` class: ``` public class MainMenu extends JPanel{ public MainMenu(){ setLayout(new BoxLayout(this , BoxLayout.Y_AXIS)); add(Box.createVerticalGlue()); JButton buttonSingle = new JButton("Single");…

Accepted Answer

You need a reference to the `CardLayout` of the `JFrame` inside your panel classes. What you can do is pass the `Frame` to the `JPanel` classes as reference, then you can use the `CardLayout` of the `Frame` in those classes to `show` or `next` etc. Something like

```
public class MainMenu {
    private CardLayout layout;
    private Frame frame;

public MainMenu(final Frame frame) {
         this.frame = frame;
         this.layout = (CardLayout)frame.getLayout();

JButton buttonSingle = new JButton("Single");     
         buttonSingle.setAlignmentX(Component.CENTER_ALIGNMENT);
         buttonSingle.addActionListener(new ActionListener(){
             @Override
             public void actionPerformed(ActionEvent e) {
                 layout.show(frame, "single");
             }
         });
    }
}
```

When you create the `MainPanel`, you need to pass `Frame.this` to it, referencing the current `Frame`

```
MainMenu menuPanel = new MainMenu(Frame.this);
```

EDIT

I just noticed your `swapView` method. So instead of use the `CardLayout` directly in the panel class, you can actually just call `swapView` in the `actionPerformed`

```
frame.swapView("single");
```

Or better yet, as to not expose the `Frame` class, you can have the `Frame` class implement an `interface` say `SwapInterface` that has a method `swapView` you need to override. And pass the `SwapInterface` to the panel classes. Something like

```
public interface SwapInterface {
    public void swapView(String view);
}

public Frame extends JFrame implements SwapInterface {
    MainMenu mainPanel = new MainMenu(Frame.this);
    ....
    @Override
    public void swapView(String view) {
        cl.show(getContentPane(), view);
    }
}

public class MainMenu extends JPanel {
    private SwapInterface swap;

public MainMenu(SwapInterface swap) {
        this.swap = swap;
        ...
        public void actionPerfomed(ActionEvent e) {
            swap.swapView("single");
        }

}
}
```

Side Note

As HovercraftFullOfEels pointed out in his comment, you should make use of String contants for the String card values so there's no mistakes. Something like

```
private static final String SINGLE_CARD = "single";
```

Then in places where you use `"single"`, use `SINGLE_CARD` instead

Java: CardLayout switching between cards

Solution

Problem