Re: GridBagLayout not behaving as specified

Qu0ll wrote:
I have a problem with GridBagLayout that I would appreciate some help with in solving.

In the following simple example I am trying to have a user label and text field plus a password label and field evenly spaced across the panel with a database field below it and a button all the way over to the right taking up very little space. To do this I have set up a 2 x 16 grid but it's not behaving as I believe I am specifying it. The problem is that the button is taking up the same amount of space as the password field even though the password field has a grid width of 4 and the button only 1. The result is that the top line is not evenly spaced and too much room is allocated for the button.

Why is this? What's wrong with my GridBagLayout definition or usage?

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class GBTest extends JFrame {

private JPanel panel = new JPanel();
private JLabel userLabel = new JLabel("User:");
private JLabel passwordLabel = new JLabel("Password:");
private JLabel dbLabel = new JLabel("Database:");
private JTextField userTextField = new JTextField();
private JTextField dbTextField = new JTextField();
private JPasswordField passwordField = new JPasswordField();
private JButton dbButton = new JButton("...");

public GBTest() {
setLayout(new BorderLayout());
panel.setLayout(new GridBagLayout());

userLabel.setText("User:");
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.gridwidth = 4;
gbc.anchor = GridBagConstraints.EAST;
gbc.insets = new Insets(0, 4, 18, 0);
gbc.ipadx = 0;
panel.add(userLabel, gbc);

gbc.gridx = 4;
gbc.gridy = 0;
gbc.gridwidth = 4;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 0.5;
gbc.weighty = 0.0;
gbc.insets = new Insets(0, 4, 18, 4);
gbc.ipadx = 40;
panel.add(userTextField, gbc);

gbc = new GridBagConstraints();
gbc.gridx = 8;
gbc.gridy = 0;
gbc.gridwidth = 4;
gbc.anchor = GridBagConstraints.EAST;
gbc.insets = new Insets(0, 4, 18, 0);
gbc.ipadx = 0;
panel.add(passwordLabel, gbc);

gbc.gridx = 12;
gbc.gridy = 0;
gbc.gridwidth = 4;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 0.5;
gbc.weighty = 0.0;
gbc.insets = new Insets(0, 4, 18, 8);
gbc.ipadx = 0;
panel.add(passwordField, gbc);

gbc.gridx = 0;
gbc.gridy = 1;
gbc.gridwidth = 4;
gbc.anchor = GridBagConstraints.EAST;
gbc.insets = new Insets(0, 4, 18, 0);
gbc.ipadx = 0;
panel.add(dbLabel, gbc);

gbc.gridx = 4;
gbc.gridy = 1;
gbc.gridwidth = 11;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 10;
gbc.weighty = 0.0;
gbc.insets = new Insets(0, 4, 18, 0);
gbc.ipadx = 0;
panel.add(dbTextField, gbc);

gbc.gridx = 15;
gbc.gridy = 1;
gbc.gridwidth = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.anchor = GridBagConstraints.EAST;
gbc.weightx = 0.0;
gbc.weighty = 0.0;
gbc.insets = new Insets(0, 4, 18, 8);
gbc.ipadx = 0;
panel.add(dbButton, gbc);

add(panel, BorderLayout.CENTER);

pack();
setPreferredSize(new Dimension(400, 250));
setSize(new Dimension(400, 250));
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
new GBTest().setVisible(true);
}
});
}
}

P.S. I am using Java 6 on Windows Vista if that's relevant. It is not PLAF dependent.


After
panel.add(dbButton, gbc);
I added
gbc.gridx = 1;
gbc.gridy = 2;
gbc.gridwidth = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.anchor = GridBagConstraints.EAST;
gbc.weightx = 0.0;
gbc.weighty = 0.0;
gbc.insets = new Insets(0, 4, 18, 8);
gbc.ipadx = 0;
for (int x=0; x < 16; x++) {
gbc.gridx=x;
panel.add(new JLabel(Integer.toString(x)), gbc);
}
The results are interesting.
I think you could use fewer than 16 columns and this might make things more predictable. I suspect some columns are shrinking to zero width because no component STARTS in them.

Personally I'd use MigLayout and have about 1/10th the code.
.

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