Possible Problem/Bug In GridBag Layout ????

Question

I've done hundreds of Gridbag layouts in the past 2 years and just noticed this weird little behavior today.....
Basically what I'm trying to do is arrange panels like this.....
+--------+--------+--------+
|        |        |        |
|   A    |    B   |   C    |
|        |        |        |
+--------+----+---+--------+
|             |            |
|     D       |      E     |
|             |            |
+-------------+------------+The obvious thing to do is to
o make the gridwidths of
B, D, E = 2
A, C = 1
D and E should each share one unit of
B's 2 width.
Tried it in my code with my real UI and it didn't work, so then I tested it
out using a Gridbag tool where you can set parameters on the fly quickly and
surely enough it did not work there either.
The GridBagLayout is refusing to split B into 2 portions for the 2nd row
to use in an unalligned fashion. I either get
+--------+--------+--------+
|        |        |        |
|   A    |    B   |   C    |
|        |        |        |
+--------+----+---+--------+
|        |                 |
|     D  |           E     |
|        |                 |
+--------+-----------------+  or
+--------+--------+--------+
|        |        |        |
|   A    |    B   |   C    |
|        |        |        |
+--------+----+---+--------+
|                 |        |
|     D           |  E     |
|                 |        |
+--------+--------+--------+ depending on the order in which I add my panels to the layout.
even though my gridx, gridy and widths and heights are properly set for
obtaining the result I want.
Can someone confirm that this is a bug in the GridBagLayout or share the trick for
getting around this?

Answer 1

Thanks for the reply - I can set the weights however
I wish and I never see box D extending even one pixel
into the A-B boundary.This does what you say...
import java.awt.*;
import javax.swing.*;
public class TestFrame extends JFrame {
  public TestFrame() {
    JPanel panel = new JPanel(new GridBagLayout());
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.gridx = 0;
    gbc.gridy = 0;
    gbc.fill = GridBagConstraints.BOTH;
    gbc.weighty = 0.5; 
    panel.add(new JButton("A"), gbc);
    gbc.gridx = 1;   
    gbc.gridwidth = 2; 
    panel.add(new JButton("B"), gbc);
    gbc.gridx = 3;   
    gbc.gridwidth = 1;
    panel.add(new JButton("C"), gbc);
    gbc.gridx = 0;
    gbc.gridy = 1;
    gbc.gridwidth = 2;
    gbc.weightx = 0.5;
    panel.add(new JButton("D"), gbc);
    gbc.gridx = 2;
    panel.add(new JButton("E"), gbc);
    getContentPane().add(panel);
    setSize(400, 300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
  public static void main(String[] args) {
    TestFrame frame = new TestFrame();
    frame.setVisible(true);
}But i'm sure it's not a satisfactory layout because button A does not want to resize horizontally at all. But of course, a mix of grid layouts does the trick:
import java.awt.*;
import javax.swing.*;
public class TestFrame extends JFrame {
  public TestFrame() {
    JPanel panel = new JPanel(new GridLayout(2, 1));
    JPanel top = new JPanel(new GridLayout(1, 3));
    top.add(new JButton("A"));
    top.add(new JButton("B"));
    top.add(new JButton("C"));
    panel.add(top);
    JPanel buttom = new JPanel(new GridLayout(1, 2));
    buttom.add(new JButton("D"));
    buttom.add(new JButton("E"));
    panel.add(buttom);
    getContentPane().add(panel);
    setSize(400, 300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
  public static void main(String[] args) {
    TestFrame frame = new TestFrame();
    frame.setVisible(true);
}