Question

I’m new to layouts and what I’m using now is a CardLayout with two different cards that currently have a background image painted on and a button. As seen below, the button is at the top of the screen and I’d like to position it somewhere closer to the bottom. My understanding is that a GridBagLayout would be the best way to accomplish that. So my first question is, is that true? And also, is it possible to do so if the JPanel I want to put the GridBagLayout on is a card in a CardLayout. I’d like to put many other objects into the GridBagLayout (if that’s the best way to do it and if it’s possible) as I get further into the project, so any advice on where the right direction to go would be greatly appreciated.

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;

public class Cards implements ActionListener {    
private JPanel cards;
private JButton button1;
private JButton button2;
private Image backgroundImage;

public void addComponentToPane(Container pane) throws IOException {
    try {           
        backgroundImage = ImageIO.read(getClass().getResource("resources/background.jpg"));         
    } catch (IOException ex) {
        ex.printStackTrace(System.err);
    }

    //create cards
    JPanel card1 = new JPanel()
    {
        @Override
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.drawImage(backgroundImage, 0, 0, null);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(
                    backgroundImage.getWidth(null),
                    backgroundImage.getHeight(null));
        }
    };
    JPanel card2 = new JPanel()
    {
        @Override
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.drawImage(backgroundImage, 0, 0, null);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(
                    backgroundImage.getWidth(null),
                    backgroundImage.getHeight(null));
        }
    };
    //create buttons
    button1 = new JButton("Button 1");
    button2 = new JButton("Button 2");
    button1.addActionListener(this);
    button2.addActionListener(this);
    //add buttons to cards
    card1.add(button1);        
    card2.add(button2);
    //create panel that contains cards
    cards = new JPanel(new CardLayout());
    cards.add(card1, "Card 1");
    cards.add(card2, "Card 2");
    pane.add(cards, BorderLayout.SOUTH);        
}

public void itemStateChanged(ItemEvent evt) {
    CardLayout cl = (CardLayout)(cards.getLayout());
    cl.show(cards, (String)evt.getItem());
}

public static void createAndShowGUI() throws IOException  {
    //create and setup window
    JFrame frame = new JFrame("Frame"); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        
    //create and setup content pane
    Cards main = new Cards();
    main.addComponentToPane(frame.getContentPane());        
    //display window
    frame.pack();       
    //frame.setResizable(false);
    frame.setVisible(true);
}

public void actionPerformed(ActionEvent ae) {
    if (ae.getSource() == button1) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, "Card 2");     
    } else if (ae.getSource() == button2) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, "Card 1");
    }        
}            

public static void main(String[] args) {
    //set look and feel
    try {
        UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    } catch (UnsupportedLookAndFeelException ex) {
        ex.printStackTrace();
    } catch (IllegalAccessException ex) {
        ex.printStackTrace();
    } catch (InstantiationException ex) {
        ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
        ex.printStackTrace();
    }                

    //schedule job for the event dispatch thread creating and showing GUI        
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {                   
                    try {
                        createAndShowGUI();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }                
        }
    });     
}   
}

Answer 1

a GridBagLayout will do what you want, yes. It’s one of the most flexible (but also one of the most complex) LayoutManagers available. Whether or not it’s the “best” way to do it depends on what other controls you want to add to your panel, whether or not you want them to resize, what you want to happen when the parent JPanel is resized, and other factors.

re: nesting JPanels with different layouts, yes. It’s perfectly fine to have a JPanel with a GridBagLayout inside of a JPanel with a CardLayout inside of a JPanel with a BorderLayout [etc…]