在JFreeChart PieChart中将与段无关的文本添加到Legend中

在JFreeChart PieChart中，将与各部分无关的文本添加到Legend中，可以通过以下步骤实现：

创建一个自定义的LegendItem，并设置其文本内容。
将自定义的LegendItem添加到PieChart的LegendItems集合中。
创建一个自定义的LegendRenderer，并重写其绘制LegendItem的方法，以便在Legend中显示自定义的文本。
将自定义的LegendRenderer设置为PieChart的LegendRenderer。

以下是一个示例代码：

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.LegendItem;
import org.jfree.chart.LegendItemCollection;
import org.jfree.chart.LegendItemSource;
import org.jfree.chart.LegendRenderer;
import org.jfree.chart.StandardChartTheme;
import org.jfree.chart.plot.PiePlot;
import org.jfree.data.general.DefaultPieDataset;
import org.jfree.data.general.PieDataset;
import org.jfree.ui.RectangleEdge;

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

public class PieChartDemo {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Pie Chart Demo");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(800, 600);

            JFreeChart chart = createChart();
            ChartPanel chartPanel = new ChartPanel(chart);
            frame.add(chartPanel);

            frame.setVisible(true);
        });
    }

    private static JFreeChart createChart() {
        // 设置图表主题
        StandardChartTheme chartTheme = new StandardChartTheme("JFree");
        chartTheme.setExtraMarkup("<mxfile version=\"3.0\">\n" +
                "  <diagram>JFreeChart</diagram>\n" +
                " <background>\n" +
                "    <fillColor>#FFFFFF</fillColor>\n" +
                "   <gradientColor>#FFFFFF</gradientColor>\n" +
                "  </background>\n" +
                "  <foreground>\n" +
                "    <fillColor>#000000</fillColor>\n" +
                "   <gradientColor>#000000</gradientColor>\n" +
                "  </foreground>\n" +
                " <stroke>\n" +
                "   <color>#000000</color>\n" +
                "   <width>1.0</width>\n" +
                "  </stroke>\n" +
                "  <font>\n" +
                "    <name>SansSerif</name>\n" +
                "    <size>12</size>\n" +
                "    <bold>false</bold>\n" +
                "    <italic>false</italic>\n" +
                "   <underline>false</underline>\n" +
                "  </font>\n" +
                " <connect>\n" +
                "   <color>#000000</color>\n" +
                "    <type>straight</type>\n" +
                "    <routing>orthogonal</routing>\n" +
                "   <arrow>none</arrow>\n" +
                "  </connect>\n" +
                "  <swimlane>\n" +
                "    <fillColor>#FFFFFF</fillColor>\n" +
                "   <gradientColor>#FFFFFF</gradientColor>\n" +
                "    <font>\n" +
                "      <name>SansSerif</name>\n" +
                "      <size>12</size>\n" +
                "      <bold>false</bold>\n" +
                "      <italic>false</italic>\n" +
                "     <underline>false</underline>\n" +
                "    </font>\n" +
                "  </swimlane>\n" +
                "  <page>\n" +
                "   <width>827</width>\n" +
                "   <height>1169</height>\n" +
                "   <margin>\n" +
                "      <top>20</top>\n" +
                "      <left>20</left>\n" +
                "     <bottom>20</bottom>\n" +
                "     <right>20</right>\n" +
                "    </margin>\n" +
                "   <background>\n" +
                "      <fillColor>#FFFFFF</fillColor>\n" +
                "     <gradientColor>#FFFFFF</gradientColor>\n" +
                "    </background>\n" +
                "    <foreground>\n" +
                "      <fillColor>#000000</fillColor>\n" +
                "     <gradientColor>#000000</gradientColor>\n" +
                "    </foreground>\n" +
                "   <stroke>\n" +
                "     <color>#000000</color>\n" +
                "     <width>1.0</width>\n" +
                "    </stroke>\n" +
                "    <font>\n" +
                "      <name>SansSerif</name>\n" +
                "      <size>12</size>\n" +
                "      <bold>false</bold>\n" +
                "      <italic>false</italic>\n" +
                "     <underline>false</underline>\n" +
                "    </font>\n" +
                "  </page>\n" +
                "</mxfile>");
        ChartFactory.setChartTheme(chartTheme);

        // 创建数据集
        PieDataset dataset = createDataset();

        // 创建饼图
        JFreeChart chart = ChartFactory.createPieChart("Pie Chart Demo", dataset, true, true, false);

        // 获取饼图的Plot
        PiePlot plot = (PiePlot) chart.getPlot();

        // 创建自定义的LegendItem
        LegendItem customLegendItem = new LegendItem("Custom Text", Color.BLACK, "Custom Text");

        // 获取饼图的LegendItems集合
        LegendItemCollection legendItems = plot.getLegendItems();

        // 将自定义的LegendItem添加到LegendItems集合中
        legendItems.add(customLegendItem);

        // 创建自定义的LegendRenderer
        LegendRenderer legendRenderer = new LegendRenderer() {
            @Override
            public Shape draw(Graphics2D g2, Rectangle2D area, int layer, int slice, int series, double value) {
                Shape shape = super.draw(g2, area, layer, slice, series, value);
                if (layer == 0 && slice == legendItems.getItemCount() - 1) {
                    g2.setColor(Color.BLACK);
                    g2.setFont(getItemFont(legendItems.getItemCount() - 1));
                    String text = customLegendItem.getLabel();
                    Rectangle2D textBounds = g2.getFontMetrics().getStringBounds(text, g2);
                    double x = area.getX() + area.getWidth() / 2 - textBounds.getWidth() / 2;
                    double y = area.getY() + area.getHeight() / 2 + textBounds.getHeight() / 2;
                    g2.drawString(text, (int) x, (int) y);
                }
                return shape;
            }
        };

        // 将自定义的LegendRenderer设置为饼图的LegendRenderer
        plot.setLegendRenderer(legendRenderer);

        return chart;
    }

    private static DefaultPieDataset createDataset() {
        DefaultPieDataset dataset = new DefaultPieDataset();
        dataset.setValue("Category 1", 25);
        dataset.setValue("Category 2", 25);
        dataset.setValue("Category 3", 25);
        dataset.setValue("Category 4", 25);
        return dataset;
    }
}

在这个示例中，我们创建了一个饼图，并向其中添加了4个部分。然后，我们创建了一个自定义的LegendItem，并将其添加到饼图的LegendItems集合中。最后，我们创建了一个自定义的LegendRenderer，并在其中绘制了自定义的文本。

这个示例中的自定义文本是"Custom Text"，你可以根据需要修改这个文本。