java - 教程中的 jFreeChart 自定义条形颜色错误

Question

我一直在到处寻找以了解如何更改每个条形颜色，因为我不喜欢默认条形颜色的渐变设置。

他们都建议使用或多或少的以下代码覆盖 BarRenderer:

class CustomRenderer extends BarRenderer {

    private Paint[] colors;

    // add your custom colors
    public CustomRenderer() {
        this.colors = new Paint[] { Color.red, Color.blue, Color.green,
                Color.yellow, Color.orange, Color.cyan, Color.magenta,
                Color.blue };
    }

    public Paint getItemPaint(final int row, final int column) {
        return this.colors[column % this.colors.length];
    }
}

要使用它，应该把

CategoryItemRenderer renderer = new CustomRenderer();
plot.setRenderer(renderer);

但我得到的只是错误

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    No enclosing instance of type ChartDemo is accessible. Must qualify the allocation with an enclosing instance of type ChartDemo (e.g. x.new A() where x is an instance of ChartDemo).

我不知道如何解决这个问题，这些答案似乎都没有承认这个问题。

下面是我的完整代码:

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.geom.Rectangle2D;
import java.io.FileOutputStream;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.BarRenderer;
import org.jfree.chart.renderer.category.CategoryItemRenderer;
import org.jfree.data.category.DefaultCategoryDataset;

import com.lowagie.text.Document;
import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.DefaultFontMapper;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfTemplate;
import com.lowagie.text.pdf.PdfWriter;

public class ChartDemo {
    public static void main(String[] args) {
        writeChartToPDF(generateBarChart(), 500, 400, "D://barchart.pdf");
    }

    public static void writeChartToPDF(JFreeChart chart, int width, int height,
            String fileName) {
        PdfWriter writer = null;
        Document document = new Document(new Rectangle(width, height));

        try {
            writer = PdfWriter.getInstance(document, new FileOutputStream(
                    fileName));
            document.open();
            PdfContentByte contentByte = writer.getDirectContent();

            PdfTemplate template = contentByte.createTemplate(width, height);
            Graphics2D graphics2d = template.createGraphics(width, height,
                    new DefaultFontMapper());
            Rectangle2D rectangle2d = new Rectangle2D.Double(0, 0, width,
                    height);

            chart.draw(graphics2d, rectangle2d);

            graphics2d.dispose();
            contentByte.addTemplate(template, 0, 0);

        } catch (Exception e) {
            e.printStackTrace();
        }
        document.close();
    }

    class CustomRenderer extends BarRenderer {

        private Paint[] colors;

        public CustomRenderer() {
            this.colors = new Paint[] { Color.red, Color.blue, Color.green,
                    Color.yellow, Color.orange, Color.cyan, Color.magenta,
                    Color.blue };
        }

        public Paint getItemPaint(final int row, final int column) {
            return this.colors[column % this.colors.length];
        }
    }

    public static JFreeChart generateBarChart() {
        DefaultCategoryDataset dataSet = new DefaultCategoryDataset();
        dataSet.setValue(100, "Population", "2");
        dataSet.setValue(78, "Population", "4");
        dataSet.setValue(62, "Population", "6");
        dataSet.setValue(50, "Population", "8");
        dataSet.setValue(39, "Population", "10");

        JFreeChart chart = ChartFactory.createBarChart("", "Team number",
                "Solved problems (%)", dataSet, PlotOrientation.VERTICAL,
                false, true, false);
        chart.setBackgroundPaint(Color.WHITE);

        final CategoryPlot plot = chart.getCategoryPlot();
        plot.setBackgroundPaint(Color.WHITE);
        plot.setDomainGridlinePaint(new Color(204, 204, 204));
        plot.setRangeGridlinePaint(new Color(204, 204, 204));

        final NumberAxis rangeAxis = (NumberAxis) plot.getRangeAxis();
        rangeAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());

        CategoryItemRenderer renderer = new CustomRenderer();
        plot.setRenderer(renderer);

        final BarRenderer renderer1 = (BarRenderer) plot.getRenderer();
        renderer1.setDrawBarOutline(false);
        renderer1.setShadowVisible(false);
        renderer1.setDrawBarOutline(false);
        renderer1.setSeriesPaint(0, Color.gray);
        renderer1.setSeriesPaint(1, Color.RED);

        return chart;
    }
}

附言。我的目标是模仿 flot.js 的风格尽可能多(平面/最小设计)。

Answer 1

您的问题与 JFreeChart 无关，而是一个 Java 问题:您有一个嵌套的非静态类 CustomRenderer。要实例化它，您需要封闭类 (ChartDemo) 的实例，或者(在您的情况下可能是更好的方法)您需要将其设为静态:

static class CustomRenderer extends BarRenderer {
  // ...
}

另见 this answer在 SO 上获取更多详细信息。

嗯，
- 马丁