条形图，其精确值打印在每个条形图的顶部

问题描述

在 JFreeChart 中是否可以完成以下任务?

Is there a way to accomplish the following in JFreeChart?

我要特别问一下每个栏顶部的印刷精美的数字.在这个特定的样本中，很容易猜出这些值，但是如果y轴成千上万甚至更多，则这种功能将非常有用.在这种情况下，条形的长度对发现确切的值没有多大帮助.

I am specifically asking about the elegantly printed numbers at the top of each bar.In this particular specimen it is easy to guess the values but such a feature would be useful if the y-axis run in the thousands or more. In such a case, the length of the bar wouldn't much help to discover the exact value.

推荐答案

是的，有可能.您需要在CategoryItemLabelGenerator中指定ItemLabelPosition.

Yes, it is possible. You need to specify ItemLabelPosition in CategoryItemLabelGenerator.

例如:

renderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator());
renderer.setBaseItemLabelsVisible(true);
ItemLabelPosition position = new ItemLabelPosition(ItemLabelAnchor.OUTSIDE12,
        TextAnchor.TOP_CENTER);
renderer.setBasePositiveItemLabelPosition(position);

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.labels.ItemLabelAnchor;
import org.jfree.chart.labels.ItemLabelPosition;
import org.jfree.chart.labels.StandardCategoryItemLabelGenerator;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.CategoryItemRenderer;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.ui.TextAnchor;

public class DemoBarChart {
    public DemoBarChart() {
        DefaultCategoryDataset dataset = new DefaultCategoryDataset();
        dataset.setValue(6, "test", "A");
        dataset.setValue(7, "test", "B");
        dataset.setValue(15, "test", "C");

        JFreeChart chart = ChartFactory.createBarChart(
                "Demo", "Test", "Value", dataset,
                PlotOrientation.VERTICAL, false, false, false);

        CategoryItemRenderer renderer = ((CategoryPlot)chart.getPlot()).getRenderer();

        renderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator());
        renderer.setBaseItemLabelsVisible(true);
        ItemLabelPosition position = new ItemLabelPosition(ItemLabelAnchor.OUTSIDE12,
                TextAnchor.TOP_CENTER);
        renderer.setBasePositiveItemLabelPosition(position);

        JFrame frame = new JFrame("DemoTable");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new ChartPanel(chart));
        frame.setLocationByPlatform(true);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new DemoBarChart();
            }
        });
    }
}

编辑(版本1.5.0):

EDIT (version 1.5.0):

在当前的JFreeChart版本(1.5.0)中，方法名称中的基本"已更改为默认".

In current JFreeChart version (1.5.0), the "Base" in methods name has changed to Default.

例如:

renderer.setDefaultItemLabelGenerator(new StandardCategoryItemLabelGenerator());
renderer.setDefaultItemLabelsVisible(true);
ItemLabelPosition position = new ItemLabelPosition(ItemLabelAnchor.OUTSIDE12,
        TextAnchor.TOP_CENTER);
renderer.setDefaultPositiveItemLabelPosition(position);

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