Question

so I want to write a matrix explorer which enables me to reorder rows and columns of a matrix.
For this porpouse I used the Jtable class. Now the problem that I have is that it is very difficult to reorder a matrix by looking at double values, so I would like to print the matrix not with the double values but with circles in which the radius of the circle represents the value. So that I can tell the difference between big values and small values quicker.

Anybody has any idea how I can turn this double values into filled circles with JTable or any table class for that matter?

Answer 1

Here’s an example of a custom renderer that implements the Icon interface to do the drawing. This approach permits easier control over the relative positioning of the text and icon. Note that the renderer scales based on the assumption of normalized values in the interval [0, 1); you may want to query your data model for the minimum and maximum values instead.

class DecRenderer extends DefaultTableCellRenderer implements Icon {

    private static final int SIZE = 32;
    private static final int HALF = SIZE / 2;
    DecimalFormat df;

    public DecRenderer(DecimalFormat df) {
        this.df = df;
        this.setIcon(this);
        this.setHorizontalAlignment(JLabel.RIGHT);
        this.setBackground(Color.lightGray);
    }

    @Override
    protected void setValue(Object value) {
        setText((value == null) ? "" : df.format(value));
    }

    @Override
    public void paintIcon(Component c, Graphics g, int x, int y) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setColor(Color.blue);
        double v = Double.valueOf(this.getText());
        int d = (int)(v * SIZE);
        int r = d / 2;
        g2d.fillOval(x + HALF - r, y + HALF - r, d, d);
    }

    @Override
    public int getIconWidth() {
        return SIZE;
    }

    @Override
    public int getIconHeight() {
        return SIZE;
    }
}