Java GridBagLayout - Equal column width in different containers

Question

I've been having a problem with the GridBagLayout for a few hours but I don't get to solve it. I have two JPanels (which contain JTextFields) in a JFrame. The first (upper) JPanel has a grid of 3 rows and 2 columns. The second (lower) JPanel has a grid of 3 rows and 3 columns. I need them to be aligned as in the next figure (white column in the upper JPanel means space; the numbers indicate the relative width) and the proportions to be consistent as the size of the window changes.

The code that I have is the next:

    import java.awt.EventQueue;
    import java.awt.FlowLayout;
    import java.awt.GridBagConstraints;
    import java.awt.GridBagLayout;
    import javax.swing.JFrame;
    import javax.swing.JLabel;
    import javax.swing.JPanel;
    import javax.swing.JTextField;
    import javax.swing.border.TitledBorder;

    public class FrameWithTwoPanels {

        private GridBagConstraints constraints;
        private JFrame frame;

        public static void main(String[] args) {
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    try {
                        FrameWithTwoPanels window = new FrameWithTwoPanels();
                        window.frame.setVisible(true);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            });
        }

        public FrameWithTwoPanels() {
            initialize();
        }

        private void initialize() {
            frame = new JFrame();
            frame.setBounds(100, 100, 800, 800);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            // Populate the frame with two Panels
            frame.setLayout(new GridBagLayout());
            GridBagConstraints c = new GridBagConstraints();
            c.gridwidth = GridBagConstraints.REMAINDER;
            c.weightx = 1;
            c.fill = GridBagConstraints.HORIZONTAL;
            c.gridy = 0;
            // PANEL 1: 3 rows and 2 columns
            frame.add(this.createPanel(3, 2), c);
            // PANEL 2: 3 rows and 3 columns
            c.gridy = 1;
            frame.add(this.createPanel(3, 3), c);

            frame.pack();
            frame.setLocationRelativeTo(null);
        }

        private JPanel createPanel(int numrows, int numcols){
            JPanel panel = new JPanel();
            panel.setLayout(new GridBagLayout());
            constraints = new GridBagConstraints();
            //constraints.fill = GridBagConstraints.BOTH;
            for(int row=0; row<numrows; row++){

                for(int col =0; col<numcols; col++){

                    JTextField component = new JTextField(row + "-" + col);

                    if(col == 0){
                        constraints.weightx = 0.5;
                    }else if(col == 1){
                        constraints.weightx = 0.4;
                    }else if(col == 2){
                        constraints.weightx = 0.1;
                    }           
                    constraints.gridy = row;
                    constraints.gridx = col;
                    panel.add(component, constraints);

                    if(numcols == 2 && col == 1){   
                        // Add auxiliar panel
                        constraints.weightx = 0.1;
                        constraints.gridx = col + 1;
                        panel.add(new JLabel());
                    }
                }   
            }
            panel.setBorder(new TitledBorder("Number of columns: " + numcols));
            return panel;       
        }
    }

The code gives the form shown in the screenshot:

Answer 1

This is a circumstance where you're actually better off using plain GridLayout. I think the following code does what you want:

private JPanel createPanel(int numrows, int numcols) {
    JPanel panel = new JPanel();
    panel.setLayout(new GridLayout(numrows, 3));
    for (int row = 0; row < numrows; row++) {
        for (int col = 0; col < numcols; col++) {
            JTextField component = new JTextField(row + "-" + col);
            panel.add(component);
            if (numcols == 2 && col == 1) {
                JPanel spacer = new JPanel();
                panel.add(spacer);
            }
        }
    }
    panel.setBorder(new TitledBorder("Number of columns: " + numcols));
    return panel;
}