JFreeChart:单击鼠标即可在散点图上显示数据 [英] JFreeChart: Displaying data on a scatter plot on mouse click

问题描述

我想在我使用JFreeChart创建的散点图上显示给定点的x，y数据.我在网上以及开发人员指南中都进行了查找，但仍然很难做到这一点.

I would like to display the x,y data for a given point on a scatter plot that I have created using JFreeChart. I have looked online and in the developer's guide as well and am still having trouble doing this.

我使用ChartFactory创建散点图

I create the scatter plot using ChartFactory

chart = ChartFactory.createScatterPlot( title, xlabel, ylabel, data, plotOrientation.VERTICAL,
    false, true, false );

我试图实现chartMouseClicked事件.

I have tried to implement the chartMouseClicked event.

public void chartMouseClicked(ChartMouseEvent event) {

 ChartEntity entity = event.getEntity();

 If (entity != null) {
    XYItemEntity ent = (XYItemEntity) entity;

    int sindex = ent.getSeriesIndex();
    int iindex = ent.getItem();

    System.out.println("x = " + data.getXValue(sindex, iindex));
 }
}

其中数据是与绘图相关的XYDataSet的实现.

where data is an implementation of the XYDataSet related to the plot.

这似乎没有给我任何数字.我在做什么错了?

This does not seem to give me any numbers. What am I doing wrong?

谢谢

推荐答案

啊，所有的红色是因为我没有检查它是否是XYItemEntity的实例.

Ah, all the red was because I was not checking to see if it was an instance of XYItemEntity.

扩展代码:

public void chartMouseClicked(ChartMouseEvent event) {

 ChartEntity entity = event.getEntity();

 if (entity != null && entity instanceof XYItemEntity) {
   XYItemEntity ent = (XYItemEntity) entity;

   int sindex = ent.getSeriesIndex();
   int iindex = ent.getItem();

   System.out.println("x = " + data.getXValue(sindex, iindex));
   System.out.println("y = " + data.getYValue(sindex, iindex));
  }
 }

现在看来可以了！

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