Grid bag layout not displaying the way I want

Question

So I have 6 panels, all of them used a grid layout. And I put them together using gridbaglayout, here is the design I wanted

Answer 1

As you wrote c.gridx = 0 and c.gridy = 0, you forgot to specify how many columns you want this JPanel to occupy. In order to specify that, you should be using c.gridwidth = 2, which tells the layout that this JPanel needs space for two columns.

To get an output like this:

Here is a small working example:

import java.awt.*;
import javax.swing.*;
// http://stackoverflow.com/questions/10968853/two-jpanels-in-jframe-one-under-other
public class GridBagLayoutExample
{
    // http://stackoverflow.com/questions/10977017/grid-bag-layout-not-displaying-the-way-i-want
    private void displayGUI()
    {
        JFrame frame = new JFrame("GridBagLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.FIRST_LINE_START;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridwidth = 2;
        gbc.weightx = 0.5;
        gbc.weighty = 0.2;

        JPanel topLeftPanel = new JPanel();
        topLeftPanel.setOpaque(true);
        topLeftPanel.setBackground(Color.DARK_GRAY);
        contentPane.add(topLeftPanel, gbc);

        gbc.gridx = 2;

        JPanel topRightPanel = new JPanel();
        topRightPanel.setOpaque(true);  
        topRightPanel.setBackground(Color.BLUE);
        contentPane.add(topRightPanel, gbc);

        gbc.gridwidth = 1;
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.weightx = 0.25;
        gbc.weighty = 0.8;

        JPanel firstPanel = new JPanel();
        firstPanel.setOpaque(true);
        firstPanel.setBackground(Color.RED);
        contentPane.add(firstPanel, gbc);

        gbc.gridx = 1;

        JPanel secondPanel = new JPanel();
        secondPanel.setOpaque(true);
        secondPanel.setBackground(Color.GREEN.darker());
        contentPane.add(secondPanel, gbc);

        gbc.gridx = 2;

        JPanel thirdPanel = new JPanel();
        thirdPanel.setOpaque(true);
        thirdPanel.setBackground(Color.WHITE);
        contentPane.add(thirdPanel, gbc);

        gbc.gridx = 3;

        JPanel fourthPanel = new JPanel();
        fourthPanel.setOpaque(true);
        fourthPanel.setBackground(Color.MAGENTA);
        contentPane.add(fourthPanel, gbc);

        frame.setContentPane(contentPane);
        frame.setSize(200, 300);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new GridBagLayoutExample().displayGUI();
            }           
        });
    }
}