How to use Card layout?

Question

I'm having a hard time trying to figure out what is a card layout. I read so many articles and implemented this small example of to see how card layout works. But I can't understand some methods(which are commented). Can someone please help me (I use commandline).

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class C_layout implements ActionListener
{
    JButton b2;
    JButton b1;
    JFrame f1;
    JPanel card1;
    JPanel card2;
    JPanel Jp;
    void Example()
    {
    f1=new JFrame("CardLayout Exercise");
    f1.setLocationRelativeTo(null);
    f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f1.setSize(500,500);
    f1.setVisible(true);

    Container cont=f1.getContentPane();
    cont.setLayout(null);

    Jp=new JPanel(new CardLayout()); //<-- How to implement card layout here (MAIN PANEL)
    f1.add(Jp);
    Jp.setLayout //<-- Not sure what means here ERROR
    card1=new JPanel(); // First panel
    Jp.add(card1);
    card2=new JPanel(); // Second panel
    Jp.add(card2);

    JLabel lb1=new JLabel("This is the first Panel");
    lb1.setBounds(250,100,100,30);
    card1.add(lb1);

    b1=new JButton("NEXT >>");
    b1.setBounds(350,400,100,30);
    b1.addActionListener(this);
    card1.add(b1);


    JLabel lb2=new JLabel("This is the second Panel");
    lb2.setBounds(250,100,100,30);
    card2.add(lb2);

    b2=new JButton("<< PREV");
    b2.setBounds(250,300,100,30);
    b2.addActionListener(this);
    card2.add(b2);
    }

    public void actionPerformed(ActionEvent e)
    {
    if(e.getSource()==b1)
    {
    CardLayout cardLayout = (CardLayout) Jp.getLayout();
    cardLayout.show(card2,"2");
    }
    if(e.getSource()==b2)
    {
    // I still haven't implemented this action listener
    }
    }
}

class LayoutDemo1
{
    public static void main(String[] args)
    {
    C_layout c=new C_layout();
    c.Example();


    }
}

Answer 1

cont.setLayout(null); is bad, bad idea, lose it quickly...

You're going to need a reference to your CardLayout in order to manage it. Start by defining a instance field of CardLayout ...

private  CardLayout cardLayout;

Now, create your instance of CardLayout and apply it to your panel...

cardLayout = new CardLayout();
Jp=new JPanel(cardLayout);

This...

Jp.setLayout //<-- Not sure what means here ERROR

doesn't do anything, it's not a valid statement as far as Java is concerned, in fact, it's actually a method, which should take a reference to the LayoutManager you want to use, but since you've already done that when you created the instance of Jp , you don't need it...

You're going to need some way to identify the components you want to show, CardLayout does this via String names, for example...

card1=new JPanel(); // First panel
Jp.add(card1, "card1");
card2=new JPanel(); // Second panel
Jp.add(card2, "card2");

Now, in your ActionListener , you want to ask CardLayout to show the required view...

public void actionPerformed(ActionEvent e)
{
    if(e.getSource()==b1)
    {
        cardLayout.show(Jp1,"card2");
    } else if(e.getSource()==b2)
    {
        cardLayout.show(Jp1,"card1");
    }
}

Note, in order for CardLayout#show to work, you need to pace it a reference of the container to which the CardLayout is assigned AND the name of the view you want to display.

See How to Use CardLayout for more details