Creating Square Buttons in Swing

Question

I would like to create something like the following in Swing:

The top part is relatively easy: I can just create a table and display it. What I'm having trouble with is the square plus and minus buttons at the bottom, which are designed to add a new item or remove the selected item respectively. In particular, I haven't been able to make the square shape because on Mac OS X and some other platforms, JButtons are rectangles with rounded corners and I can't find a way to change that. Also, I'm wanting to make sure it's a perfect square and without any space in between buttons.

How can this be accomplished in a cross-platform way on Swing?

Answer 1

JButtons are rectangles with rounded corners and I can't find a way to change that.

Change the Border:

button.setBorder( new LineBorder(Color.BLACK) );

Edit.

Another approach is to create your own icon from an existing button. Something like the following:

JButton button = new JButton("+");
Dimension size = button.getPreferredSize();
size.x += 6;
size.y += 6;
button.setPreferredSize(size);
Rectangle rectangle = new Rectangle(3, 3, size.x - 3, size.y - 3);
ScreenImage buttonImage = ScreenImage(button, rectangle);
ImageIcon icon = new ImageIcon(buttonImage);

JButton plus = new JButton(icon);
plus.setBorder( ... );

The above code should create an image of your button on any platform. I increased the preferred size to avoid taking an image of the border.

You will need to use the Screen Image class.

Answer 2

This is most easily achieved by returning a preferred size that is NxN - where N is the larger of preferred width or height.

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;

class SquareButton extends JButton {

    SquareButton(String s) {
        super(s);
    }

    @Override
    public Dimension getPreferredSize() {
        Dimension d = super.getPreferredSize();
        int s = (int)(d.getWidth()<d.getHeight() ? d.getHeight() : d.getWidth());
        return new Dimension (s,s);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                JComponent gui = new JPanel(new FlowLayout());
                for (int ii=0; ii<5; ii++) {
                    gui.add(new SquareButton("" + ii));
                }

                gui.setBorder(new EmptyBorder(4, 8, 4, 8));

                JFrame f = new JFrame("Square Buttons");
                f.add(gui);
                // Ensures JVM closes after frame(s) closed and
                // all non-daemon threads are finished
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                // See http://stackoverflow.com/a/7143398/418556 for demo.
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // should be done last, to avoid flickering, moving,
                // resizing artifacts.
                f.setVisible(true);
            }
        };

        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
        SwingUtilities.invokeLater(r);
    }
}