如何使用循环更改多个椭圆的颜色（JFreeChart）

Question

我使用如下所示的循环绘制了多个椭圆，并且为所有椭圆使用一种颜色的结果非常完美，但我的目标是为每个椭圆着色不同的颜色。有没有办法让Color.BLUE属性在每次迭代中改变它的值？

for (int i = 0; i < 3; i++)
{
    XYShapeAnnotation unitCircle1 = new XYShapeAnnotation(
        new Ellipse2D.Double((FinalArayOfOptpar[s][i] - Math.abs(FinalArayOfOptpar[s][i + 2])),
            (FinalArayOfOptpar[s][i + 1] - Math.abs(FinalArayOfOptpar[s][i + 3])),
            Math.abs(FinalArayOfOptpar[s][i + 2] * 2.0), Math.abs(FinalArayOfOptpar[s][i + 3] * 2.0)),
        new BasicStroke(0.5f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_MITER,
            10.2f), Color.BLUE);
    xyPlot.addAnnotation(unitCircle1);
}

Answer 1

将创建数十个 XYShapeAnnotations...因此创建多个 XYShapeAnnotation 实例对我的目的不起作用。

幸运的是，XYShapeAnnotation 的实例很小——在下面的示例中，每个实例只有 48 个字节。您一定要profile。

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.geom.Ellipse2D;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartFrame;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.annotations.XYShapeAnnotation;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see https://stackoverflow.com/a/35236100/230513
 */
public class AnnotationTest {

    private static final BasicStroke stroke = new BasicStroke(2.0f);
    private static final int N = 16;
    private static final int S = 8;

    public static void main(String[] args) {
        EventQueue.invokeLater(new AnnotationTest()::display);
    }

    private void display() {
        XYDataset data = createDataset();
        JFreeChart chart = ChartFactory.createXYLineChart("ArcTest", "X", "Y",
            data, PlotOrientation.VERTICAL, true, true, false);
        XYPlot plot = chart.getXYPlot();
        XYLineAndShapeRenderer renderer
            = (XYLineAndShapeRenderer) plot.getRenderer();
        renderer.setBaseShapesVisible(true);
        for (int i = 0; i < N; i++) {
            double x = data.getXValue(0, i) - S / 2;
            double y = data.getYValue(0, i) - S / 2;
            Ellipse2D.Double ellipse = new Ellipse2D.Double(x, y, S, S);
            Color color = Color.getHSBColor((float) i / N, 1, 1);
            renderer.addAnnotation(new XYShapeAnnotation(ellipse, stroke, color));
        }
        ChartFrame frame = new ChartFrame("Test", chart);
        frame.pack();
        frame.setVisible(true);
    }

    private static XYDataset createDataset() {
        XYSeriesCollection result = new XYSeriesCollection();
        XYSeries series = new XYSeries("ArcTest");
        for (int i = 0; i < N; i++) {
            series.add(i * S, i * S);
        }
        result.addSeries(series);
        return result;
    }
}