How to draw legend as a table with JFreeCharts?

Question

I'm able to plot this chart like this:

But I want to plot it like this, which means at the bottom of the chart and as a table (at least look like one).

Here is my code:

package charts;

import java.awt.*;
import java.io.*;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.block.BlockBorder;
import org.jfree.chart.labels.PieSectionLabelGenerator;
import org.jfree.chart.labels.StandardPieSectionLabelGenerator;
import org.jfree.chart.plot.PiePlot;
import org.jfree.chart.title.LegendTitle;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.general.DefaultPieDataset;
import org.jfree.ui.RectangleEdge;

public class PieChart {
    public static void main( String[ ] args ) throws Exception
    {

        DefaultPieDataset dataset = new DefaultPieDataset();
        dataset.setValue("A", new Double( 36.95 ));
        dataset.setValue("B", new Double( 31.51 ));
        dataset.setValue("C", new Double( 12.44 ));
        dataset.setValue("D", new Double( 6.41 ));
        dataset.setValue("E", new Double( 2.76 ));
        dataset.setValue("F", new Double( 2.29 ));
        dataset.setValue("G", new Double( 1.71 ));
        dataset.setValue("H", new Double(1.21));
        dataset.setValue("I", new Double(4.71));

        JFreeChart chart = ChartFactory.createPieChart(
                "", // chart title
                dataset, // dataset
                true, // legends
                true, // tooltips
                false); // urls

        // remove legend border
        chart.getLegend().setFrame(BlockBorder.NONE);

        PiePlot plot = (PiePlot) chart.getPlot();
        plot.setSimpleLabels(true);

        PieSectionLabelGenerator generator = new StandardPieSectionLabelGenerator("{2}");
        plot.setLabelGenerator(generator);

        // background
        plot.setBackgroundPaint(Color.WHITE); //
        plot.setOutlineVisible(false); // remove image border

        // label
        plot.setLabelFont(new Font("Courier New", Font.BOLD, 16));
        plot.setLabelPaint(Color.WHITE);

        Color transparent = new Color(0.0f, 0.0f, 0.0f, 0.0f);
        plot.setLabelBackgroundPaint(transparent); //background
        plot.setLabelOutlinePaint(transparent); //border
        plot.setLabelShadowPaint(transparent); //shadow

        // legend
        plot.setLegendLabelGenerator(new StandardPieSectionLabelGenerator("{0}: {1}"));

        // sections
        // use gradients and white borders for the section colours
        plot.setSectionPaint("A",  new Color(126, 208, 150));
        plot.setSectionPaint("B", new Color(41, 157, 135));
        plot.setSectionPaint("C", new Color(25, 144, 212));
        plot.setSectionPaint("D", new Color(95, 85, 25));
        plot.setSectionPaint("E", new Color(22, 90, 63));
        plot.setSectionPaint("F", new Color(134, 125, 25));
        plot.setSectionPaint("G", new Color(226, 200, 14));
        plot.setSectionPaint("H", new Color(241, 172, 18));
        plot.setSectionPaint("I", new Color(245, 200, 51));
        plot.setBaseSectionOutlinePaint(Color.WHITE);
        plot.setSectionOutlinesVisible(true);

        // chart title at the bottom
        TextTitle legendText = new TextTitle("THIS IS JUST A TEST");
        legendText.setPosition(RectangleEdge.BOTTOM);
        chart.addSubtitle(legendText);

        LegendTitle legend = chart.getLegend();
        legend.setPosition(RectangleEdge.RIGHT);

        int width = 640; /* Width of the image */
        int height = 480; /* Height of the image */
        File pieChart = new File( "PieChart.png" );
        ChartUtilities.saveChartAsPNG(pieChart, chart, width, height);
    }
}

Answer 1

Here is how to customize the legend layout:

// remove default legend
chart.removeLegend();

// create and add legend
LegendTitle legend = new LegendTitle(plot, new GridArrangement(dataset.getItemCount(), 1), new GridArrangement(1, 1));
legend.setPosition(RectangleEdge.BOTTOM);
chart.addLegend(legend);

// add text title after the legend

However, customizing the legend items layout exactly as you want is much more difficult. You would need to override a bunch of methods, like createLegendItemBlock() in LegendTitle, and manually fiddle with the Block and Arrangement API of JFreechart.

Alternatively you could completely bypass the JFreechart API, and generate your own legend panel, using Swing components. Check-out this example.