JFreeChart在折线图中显示值

Question

如何在折线图中显示系列的值。

我当前的代码

public void renderChart(String variation, OutputStream stream) throws Exception {
    boolean rotate = "rotate".equals(variation); // add ?variation=rotate to the URL to rotate the chart
    JFreeChart chart = generateChart(rotate);
    ChartUtilities.writeChartAsPNG(stream, chart, 750, 400);
}

private JFreeChart generateChart(boolean rotate) {
    DefaultCategoryDataset data = ChartData.getDataset();
    JFreeChart chart = ChartFactory.createLineChart("example graph", // title
            "x-axis", // x-axis label
            "y-axis", // y-axis label
            data, rotate ? PlotOrientation.HORIZONTAL : PlotOrientation.VERTICAL, true, // legend displayed
            true, // tooltips displayed
            false); // no URLs*/
    CategoryPlot plot = (CategoryPlot) chart.getPlot();
    LineAndShapeRenderer renderer = (LineAndShapeRenderer) plot.getRenderer();
    renderer.setShapesVisible(true);
    DecimalFormat decimalformat1 = new DecimalFormat("##");
    renderer.setItemLabelGenerator(new StandardCategoryItemLabelGenerator("{2}", decimalformat1));
    renderer.setItemLabelsVisible(true);
    renderer.setSeriesVisible(true);
    return chart;
}

谁能告诉我如何显示此值

Answer 1

为了运行您的代码，我制作了main方法，并制作了ChartData.getDataset()方法来创建一些示例数据。您的代码也可以正常工作。所以我想您的问题是您没有我刚才提到的这两种方法。

这里是创建简单测试数据集的方式：

class ChartData {
    public static DefaultCategoryDataset getDataset() {
        DefaultCategoryDataset dataset = new DefaultCategoryDataset();
        dataset.addValue(1, "Foo", "A");
        dataset.addValue(10, "Foo", "B");
        dataset.addValue(5, "Foo", "C");
        dataset.addValue(2, "Bar", "A");
        dataset.addValue(3, "Bar", "B");
        dataset.addValue(8, "Bar", "C");
        return dataset;
    }
}

这是main方法：

public class JFreeChartSnippet {

    ////                                    ////
    // Copy your code from your question here //
    ////                                    ////

    public static void main(String[] args) throws Exception {
        new JFreeChartSnippet().renderChart("rotate", new FileOutputStream("foobar.png"));
    }
}

现在您应该在文件foobar.png中看到一些输出：

Answer 2

[enter image description here import java.text.DecimalFormat;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartFrame;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.CategoryItemRenderer;

import org.jfree.chart.renderer.category.LineAndShapeRenderer;
import org.jfree.chart.labels.StandardCategoryItemLabelGenerator;
import org.jfree.data.category.DefaultCategoryDataset;

public class GraficaLineaChart {

    public static void main(String[] args) {
    DefaultCategoryDataset dataset = new DefaultCategoryDataset();

    dataset.setValue(6, "2019", "Alex");
    dataset.setValue(7, "2020", "Alex");

    dataset.setValue(8, "2019", "Carmen");
    dataset.setValue(5, "2020", "Carmen");

    dataset.setValue(12, "2019", "Tony");
    dataset.setValue(9, "2020", "Tony");

    JFreeChart chart = ChartFactory.createLineChart( "Promedio de calificaciones  2019-2020", "Alumnos", "Calificaciones", dataset, PlotOrientation.VERTICAL, true, true, false); 

    CategoryPlot plot = chart.getCategoryPlot();
    LineAndShapeRenderer renderer = (LineAndShapeRenderer) plot.getRenderer();
    renderer.setShapesVisible(true);
    DecimalFormat decimalformat1 = new DecimalFormat("##");
    renderer.setItemLabelGenerator(new StandardCategoryItemLabelGenerator("{2}", decimalformat1));

    renderer.setItemLabelsVisible(true);
    renderer.setSeriesVisible(true);

    //Mostramos la grafica en pantalla
    ChartFrame frame = new ChartFrame("Ejemplo
    Grafica de Lineas", chart);
    frame.pack();
    frame.setVisible(true);
    }
}