JButton没有出现在GridBagLayout中

Question

I am trying to create a 10 x 10 grid of perfectly square JButtons with no spacing in between. I believe that in order to accomplish this my only solution is the GridBagLayout. However, I'm stuck on step one - I can't get them to appear when I use a loop. Here is what I have.

Class with main() function:

public class PixelArtist {
    public static void main(String[] args) {
        try {
            PixelArtistGUI frame = new PixelArtistGUI();
            frame.setVisible(true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

GUI Handler class:

public class PixelArtistGUI extends JFrame {
    public PixelArtistGUI() {
        setTitle("PixelArtist");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        JPanel contentPane = new JPanel(new GridBagLayout());
        this.add(contentPane);
        contentPane.setSize(500, 500);
        GridBagConstraints c = new GridBagConstraints();

        JButton b;

        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 10; i++) {
                b = new JButton();
                c.gridx = i;
                c.gridy = j;
                contentPane.add(b,c);
            }
        }

    }
}

All the above does is open a very small, seemingly empty JFrame shown here:

The last thing I have done is I added the contentPane.setSize(500, 500); line, but that does not seem to be making any difference.

I am sure it's something simple - thank you in advance for the help.

Answer 1

This should show something (I tested it). Check for the lines // <<<<<< where I added statements:

• Set the panel as the content pane
• Set the preferred size for the content pane
• Calling pack to size the frame to the preferred size
• Show the frame using SwingUtilities.invokeLater to play nice with the Event Dispatching Thread

---

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

public class PixelArtistGUI extends JFrame {
    public PixelArtistGUI() {
        setTitle("PixelArtist");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        JPanel contentPane = new JPanel(new GridBagLayout());
        setContentPane(contentPane); // <<<<<
        contentPane.setPreferredSize(new Dimension(500, 500)); // <<<<<
        GridBagConstraints c = new GridBagConstraints();

        JButton b;

        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 10; i++) {
                b = new JButton();
                c.gridx = i;
                c.gridy = j;
                contentPane.add(b,c);
            }
        }
        pack(); // <<<
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() { // <<<
            @Override
            public void run() {
                try {
                    new PixelArtistGUI().setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

Answer 2

You should at least use

public void add(Component comp,Object constraints)

Ie:

contentPane.add(b,c);

And as FredK says add the contentPane to the frame