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;
}

任何人都可以告诉我们如何在这个

中显示价值

Answer 1

为了运行您的代码我创建了一个main方法，并创建了一个方法ChartData.getDataset()来创建一些示例数据。你的代码工作得很好。 所以我猜你的问题是你没有我刚才提到的这两种方法。

以下是创建简单测试数据集的方法：

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 //单击以显示图形

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) {
        //Create the object dataset to put the values to draw the line
        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");

//Create the chart object for the type Line Chart. Tip: the second field "true" is very important to the draw the value top the line

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

//Create of the renderer object to the draw point and the value
        LineAndShapeRenderer renderer = (LineAndShapeRenderer) plot.getRenderer();
        renderer.setShapesVisible(true);

//Define the format to the value to the draw
        DecimalFormat decimalformat1 = new DecimalFormat("##");
        renderer.setItemLabelGenerator(new StandardCategoryItemLabelGenerator("{2}", decimalformat1));

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

        //Show of the graph in the desktop 
        ChartFrame frame = new ChartFrame("Ejemplo
        Grafica de Lineas", chart);
        frame.pack();
        frame.setVisible(true);
        }
    }