Border around cells in JTable

[Mathias Nilsson]

Can I set a border around a group of cells. Not just one cell but around say 4 cells.

// Mathias

[Jeff Albertson]

The short answer is yes. It's just a matter of configuring the cell renderers
you are using to have borders that draw parts of a larger "zone" border.
Here is some GUI code I wrote for a su doku app.

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
 
public class ZoneBorder implements Border {
    private static final int WIDTH = 1;
    private Color colorN, colorE, colorS, colorW;
 
    public ZoneBorder(Color colorN, Color colorE, Color colorS, Color colorW) {
        this.colorN=colorN;
        this.colorE=colorE;
        this.colorS=colorS;
        this.colorW=colorW;
    }
 
    public boolean isBorderOpaque() {
        return false;
    }
 
    public Insets getBorderInsets(Component c) {
        return new Insets(WIDTH,WIDTH,WIDTH,WIDTH);
    }
 
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        Color old = g.getColor();
        if (colorN != null) {
            g.setColor(colorN);
            g.fillRect(x, y, width, WIDTH);
        }
        if (colorE != null) {
            g.setColor(colorE);
            g.fillRect(x+width-WIDTH, y, WIDTH, height);
        }
        if (colorS != null) {
            g.setColor(colorS);
            g.fillRect(x, y+height-WIDTH, width, WIDTH);
        }
        if (colorW != null) {
            g.setColor(colorW);
            g.fillRect(x, y, WIDTH, height);
        }
        g.setColor(old);
    }
}

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.table.*;
 
public class TableExample{
    public static void main(String[] args) {
        final JFrame f = new JFrame("TableExample");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(createTable());
        f.pack();
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
 
    static JComponent createTable() {
        final JTable table = new JTable(9,9) {
            private static final long serialVersionUID = 0;
 
            Color B = Color.BLACK;
            Color C = new Color(0,0,0,0);
            final Border[][] borders = {
                {new ZoneBorder(B,C,C,B), new ZoneBorder(B,C,C,C), new ZoneBorder(B,B,C,C)},
                {new ZoneBorder(C,C,C,B), new ZoneBorder(C,C,C,C), new ZoneBorder(C,B,C,C)},
                {new ZoneBorder(C,C,B,B), new ZoneBorder(C,C,B,C), new ZoneBorder(C,B,B,C)}
            };
 
            public Component prepareRenderer(TableCellRenderer renderer, int row, int column) {
                Component result = super.prepareRenderer(renderer, row, column);
                if (result instanceof JComponent) {
                    ((JComponent) result).setBorder(borders[row%3][column%3]);
                }
                return result;
            }
        };
        table.setRowHeight(28);
        table.setGridColor(Color.BLACK);
        TableColumnModel tcm = table.getColumnModel();
        for(int c = 0; c<table.getColumnCount(); ++c) {
            TableColumn tc = tcm.getColumn(c);
            tc.setPreferredWidth(28);
        }
        JPanel inner = new JPanel(new GridLayout());
        inner.setBorder(BorderFactory.createLineBorder(Color.BLACK, 3));
        inner.add(table);
        return inner;
    }
}

[Mathias Nilsson]

Thank you very much!!

I will try to get into your code.

// Mathias

[Mathias Nilsson]

Hummm .... another question about this subject.

I only want the border to be 1 pixel in width not 2.

// Mathias

[Jeff Albertson]

Like this?

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.table.*;
 
public class TableExample{
    public static void main(String[] args) {
        final JFrame f = new JFrame("TableExample");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(createTable());
        f.pack();
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
 
    static JComponent createTable() {
        final Color B = Color.BLACK;
        final Color C = new Color(0,0,0,0);
 
        final JTable table = new JTable(9,9) {
            private static final long serialVersionUID = 0;
 

            final Border[][] borders = {
                {new ZoneBorder(C,C,C,C), new ZoneBorder(C,C,C,C), new ZoneBorder(C,B,C,C)},
                {new ZoneBorder(C,C,C,C), new ZoneBorder(C,C,C,C), new ZoneBorder(C,B,C,C)},
                {new ZoneBorder(C,C,B,C), new ZoneBorder(C,C,B,C), new ZoneBorder(C,B,B,C)}
            };
 
            public Component prepareRenderer(TableCellRenderer renderer, int row, int column) {
                Component result = super.prepareRenderer(renderer, row, column);
                if (result instanceof JComponent) {
                    ((JComponent) result).setBorder(borders[row%3][column%3]);
                }
                return result;
            }
        };
        table.setRowHeight(28);
        table.setGridColor(Color.BLACK);
 
        table.setShowGrid(false);
        table.setIntercellSpacing(new Dimension(0,0));
 
        TableColumnModel tcm = table.getColumnModel();
        for(int c = 0; c<table.getColumnCount(); ++c) {
            TableColumn tc = tcm.getColumn(c);
            tc.setPreferredWidth(28);
        }
        JPanel inner = new JPanel(new GridLayout());
        inner.setBorder(new ZoneBorder(B,C,C,B));
        inner.add(table);
        return inner;
    }
}

The new methods I used here are JTable's setShowGrid and setIntercellSpacing.

[Mathias Nilsson]

Thanks alot

I'm not very good at this but if you have time explaining the code then you are most welcome.

// Mathias

[Jeff Albertson]

Can you narrow down your question? which lines need explanation?