java - GridBagLayout panels alignment

Question

I have a little issue with the GridBag Layout Manager. I am trying to display 9 panels like this:

To do so, I separated the Grid like this:

For the panels 1 to 7 there is no problem, they show up just as I want. But the issue starts with the panels S8 and S9. As you can see, the S8 and S9 takes up half the frame, but I can't make it display like this. The S8 ends at the start of S4, and the S9 begins at the end of S4, I cannot handle the half space.

Only way I figured out is to put the S8 and S9 panel in another panel which takes all the frame width - but surely there must be a proper way to display these two panels without putting them in another panel!

Here is the code:

workzone.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.NORTHWEST;
c.fill = GridBagConstraints.BOTH;
c.weightx = 0.5;
c.weighty = 0.5;
c.insets = new Insets(0,0,0,0);

//S1
c.gridx = 0;
c.gridy = 0;
c.gridwidth = 2;
c.gridheight = 2;
workzone.add(S1, c);

//S2
c.gridx = 2;
c.gridy = 0;
c.gridwidth = 2;
c.gridheight = 1;
workzone.add(S2, c);

//S3
c.gridx = 2;
c.gridy = 1;
c.gridwidth = 2;
c.gridheight = 1;
workzone.add(S3, c);

//S4
c.gridx = 4;
c.gridy = 0;
c.gridwidth = 2;
c.gridheight = 2;
workzone.add(S4, c);

//S5
c.gridx = 7;
c.gridy = 0;
c.gridwidth = 1;
c.gridheight = 1;
workzone.add(S5, c);

//S6
c.gridx = 7;
c.gridy = 1;
c.gridwidth = 2;
c.gridheight = 1;
workzone.add(S6, c);

//S7
c.gridx = 8;
c.gridy = 0;
c.gridwidth = 2;
c.gridheight = 2;
workzone.add(S7, c);

//S8
c.gridx = 0;
c.gridy = 2;
c.gridwidth = 5;
c.gridheigth = 1;
workzone.add(S8, c);

//S9
c.gridx = 6;
c.gridy = 2;
c.gridwidth = 5;
c.gridheight = 1;
workzone.add(S9, c);

Any ideas and propositions are welcome !

Answer 1

Good question. It took me little to crack it, but I got it. Normally, I would have put setions 1-7 in a top panel, and sections 8-9 in a bottom panel, but I liked the challange of 1 panel with GBL. [bored]

The problem is that section 4 (column indexes 4 and 5) is not well-defined for GBL, so section 8 doesn't know how far out to go to cover it's fifth column (index 4) so it then just stops after column index 3.

So, I added 2 zero-height spacers in the columns that make up section 4 and it worked. Comment out the 2 lines marked SPACERS to see what I mean:

EDIT: added fix suggested by @SheridanVespo

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class GridBagDemo2 implements Runnable
{
  private Color[] colors = {Color.BLACK, Color.BLUE, Color.CYAN, Color.GRAY,
                            Color.GREEN, Color.MAGENTA, Color.ORANGE,
                            Color.PINK, Color.RED, Color.YELLOW};

  private JPanel panel;
  private GridBagConstraints gbc;

  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new GridBagDemo2());
  }

  public void run()
  {
    panel = new JPanel(new GridBagLayout());
    gbc = new GridBagConstraints();

    add(0,0, 2,2, "1");
    add(2,0, 2,1, "2");
    add(2,1, 2,1, "3");
    add(4,0, 2,2, "4");
    add(6,0, 2,1, "5");
    add(6,1, 2,1, "6");
    add(8,0, 2,2, "7");
    add(0,2, 5,1, "8");
    add(5,2, 5,1, "9");

    // SPACERS: define the 2 columns that is section "4"
    add(4,3, 1,1, "");
    add(5,3, 1,1, "");

    JFrame frame = new JFrame("Grig Bag");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(panel);
    frame.pack();
    frame.setVisible(true);
  }

  private void add(int x, int y, int colspan, int rowspan, String name)
  {
    gbc.gridx = x;
    gbc.gridy = y;
    gbc.gridwidth = colspan;
    gbc.gridheight = rowspan;
    gbc.weightx = .1;
    gbc.weighty = .1;
    gbc.anchor = GridBagConstraints.CENTER;
    gbc.fill = GridBagConstraints.BOTH;

    // using another panel for illustrative purposes only
    JPanel p = new JPanel();

    if (!name.equals(""))
    {
      gbc.weightx = 1;                          // @SheridanVespo fix
      int index = Integer.parseInt(name);
      JLabel label = new JLabel("Panel " + name);
      p.add(label);
      p.setBackground(colors[index]);
      panel.add(p, gbc);
    }
    else
    {
      gbc.weightx = 0.5;                        // @SheridanVespo fix
      gbc.weighty = 0;  // don't allow the spacer to grow 
      gbc.fill = GridBagConstraints.NONE;
      panel.add(Box.createHorizontalGlue(), gbc);
    }
  }
}