javaswingawtgrid-layoutgridbaglayout

Struggling to create an uneven grid in Swing

I have a working application that uses GridLayout to make a 2 by 2 grid, each containing a JPanel.

The GridLayout worked just fine, I just did mainPanel.setLayout(new GridLayout(2, 2)), and everything worked out just fine.

However, I noticed that 2 of my components were a little cramped (horizontally) inside of the grid. I know that I could swap my layout to using CardLayout or something instead, but the application I am building is more of a dashboard, and therefore, having all the elements viewable at once is rather important. And this lack of horizontal space is for a maximized window, so maximizing isn't an option.

Well, as it turns out, the other 2 components had horizontal space to spare, so I thought to myself, "Why don't I just move the 2 big components into the same column, the 2 small components into the other column, and then resize the column so that they both have the adequate space they need?"

Here is a simple visual representation of what I mean.

Image of 2 grids, demonstrating the current state on the left side, and my desired state on the right side. Left side is an evenly sized grid. Right side is a grid where the left column is much wider than the right column.

As it turns out, GridLayout (understandably) does not provide this functionality, so I decided to cycle through the different Swing layouts listed in this tutorial. Of all the layouts, GridBagLayout seemed to be the best fit for my needs.

So, I took a look at the tutorial for GridBagLayout. My first goal was to recreate what I already have with GridLayout, then manipulate that solution until it looks like what I needed.

Here is my first, naive attempt. This was after skimming through the tutorial.

import java.awt.*;
import javax.swing.*;
import java.util.function.*;

public class GUI
{

    private final JFrame frame = new JFrame();

    public GUI()
    {

        this.frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        this.frame.setExtendedState(JFrame.MAXIMIZED_BOTH);

        this.frame.add(createPanel());

        this.frame.setVisible(true);

    }

    private static JPanel createPanel()
    {

        final JPanel grid = new JPanel();
        grid.setBorder(BorderFactory.createLineBorder(Color.MAGENTA));

        final java.util.function.Supplier<JPanel> createButtonGrid =
         () ->
         {

            final JPanel buttonGrid = new JPanel(new java.awt.GridLayout(4, 4));

            for (int i = 0; i < 16; i++)
            {

               buttonGrid
                  .add
                  (
                     new
                        JButton
                        (
                           """
                           <html>
                           THIS IS BUTTON TEXT<br>
                           THIS IS BUTTON TEXT<br>
                           THIS IS BUTTON TEXT<br>
                           THIS IS BUTTON TEXT
                           </html>
                           """
                        )
                  );

            }

            return buttonGrid;

         };

        TOP_LEFT:
        {

            final GridBagConstraints c = new GridBagConstraints();

            c.gridx = 0;
            c.gridy = 0;

            final JPanel tempPanel = createButtonGrid.get();
            tempPanel.setBorder(BorderFactory.createLineBorder(Color.RED));
            grid.add(tempPanel, c);

        }


        TOP_RIGHT:
        {

            final GridBagConstraints c = new GridBagConstraints();

            c.gridx = 1;
            c.gridy = 0;

            final JPanel tempPanel = createButtonGrid.get();
            tempPanel.setBorder(BorderFactory.createLineBorder(Color.ORANGE));
            grid.add(tempPanel, c);

        }

        BOTTOM_LEFT:
        {

            final GridBagConstraints c = new GridBagConstraints();

            c.gridx = 0;
            c.gridy = 1;

            final JPanel tempPanel = createButtonGrid.get();
            tempPanel.setBorder(BorderFactory.createLineBorder(Color.GREEN));
            grid.add(tempPanel, c);

        }

        BOTTOM_RIGHT:
        {

            final GridBagConstraints c = new GridBagConstraints();

            c.gridx = 1;
            c.gridy = 1;

            final JPanel tempPanel = createButtonGrid.get();
            tempPanel.setBorder(BorderFactory.createLineBorder(Color.BLUE));
            grid.add(tempPanel, c);

        }

        return grid;

    }

}

When I run this, already things are a bit different than expected. The components are all scrunched in the middle.

GridLayout ensures that each component takes up all available vertical and horizontal space. I need this if I am going to be using GridBagLayout. After all, the entire reason why I just switched over to GridBagLayout was to be able to squeeze out just a little more horizontal width. What I have now is a step backwards.

So, I read through the tutorial again, thoroughly this time, and saw the following quote.

fill

Used when the component's display area is larger than the component's requested size to determine whether and how to resize the component. Valid values (defined as GridBagConstraints constants) include NONE (the default), HORIZONTAL (make the component wide enough to fill its display area horizontally, but do not change its height), VERTICAL (make the component tall enough to fill its display area vertically, but do not change its width), and BOTH (make the component fill its display area entirely).

Reading that, I tried to add a c.fill = GridBagConstraints.BOTH; for each of the components. However, the result was 100% the same. No difference between the first version and the second version.

Reading through a second time, I noticed the following quote.

A GridBagLayout places components in a grid of rows and columns, allowing specified components to span multiple rows or columns. Not all rows necessarily have the same height. Similarly, not all columns necessarily have the same width. Essentially, GridBagLayout places components in rectangles (cells) in a grid, and then uses the components' preferred sizes to determine how big the cells should be.

Reading that, I started trying out different preferred sizes. That had an impact, but not quite what I wanted. Now my GUI doesn't resize correctly. The preferredSize that I provide is what the component stays at. I need my components to take up all horizontal space. If my display area increases or decreases in size, I need my components to follow suit while maintaining proportion to each other.

So, I tried to reread the tutorial again and found the following quote.

For example, to make button 4 be extra tall, the example has this code:

c.ipady = 40;

So, I tried ipadx, but it didn't change anything. It looked the same as my first 2 attempts.

Finally, I tried to reread the tutorial again, but nothing else seemed like it would work for my solution.

Any suggestions?

Solution

  • I recreated your GUI to get the following.

    enter image description here

    The components expand when you expand the window.

    enter image description here

    Generally, when creating a Java Swing GUI, you start by picking out the Swing components you want to use, like JTextFields, JLabels, and JButtons. You place these components in one or more JPanels. You place one or more JPanels in your JFrame.

    You have to take into account the size of the monitors that will display your Swing GUI. Some monitors may be too small to display everything. In Windows, you have to take display scaling into account as well.

    Oracle has a helpful tutorial, Creating a GUI With Swing. Skip the Learning Swing with the NetBeans IDE section.

    All Swing applications must start with a call to the SwingUtilities invokeLater method. This method ensures that the Swing components are created and executed on the Event Dispatch Thread.

    Each individual JPanel uses a GridBagLayout. The main JPanel uses a GridBagLayout.

    Here's the complete runnable code.

    import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class GridBagLayoutTest5 implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new GridBagLayoutTest5());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createMainPanel(), BorderLayout.CENTER);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createMainPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;

        gbc.gridx = 0;
        gbc.gridy = 0;
        panel.add(createButtonPanel(Color.BLUE,
                "This is really long button text"), gbc);

        gbc.gridx++;
        panel.add(createButtonPanel(Color.RED, "This is button text"), gbc);

        gbc.gridx = 0;
        gbc.gridy++;
        panel.add(createButtonPanel(Color.BLUE,
                "This is really long button text"), gbc);

        gbc.gridx++;
        panel.add(createButtonPanel(Color.RED, "This is button text"), gbc);

        return panel;
    }

    private JPanel createButtonPanel(Color color, String text) {
        JPanel panel = new JPanel(new GridBagLayout());
        panel.setBorder(BorderFactory.createLineBorder(color, 5));
        
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.fill = GridBagConstraints.BOTH;
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;

        for (int index = 0; index < 16; index++) {
            gbc.gridx = index % 4;
            gbc.gridy = index / 4;
            panel.add(createTextButton(text), gbc);
        }

        return panel;
    }

    private JButton createTextButton(String text) {
        String s = "<html>" + text + "<br>" + text + "<br>";
        s += text + "<br>" + text + "<br></html>";
        JButton button = new JButton(s);
        return button;
    }

}