How to get the coordinates of a point on mouse click with JFreeChart?

Question

I am trying to get the coordinates of the point clicked with the mouse on a scatter plot graph.

When you click on a point, "Click event!" and the coordinates are printed on the console. When you click on the "Test" button, "Test" and the coordinates are printed on the console.

Problem: The coordinates printed after clicking the button are up-to-date. The coordinates printed after clicking on a point are the one of the previously selected point.

How can I fix that (so when I click on a point, the coordinates of the new selected point are displayed) ?

package graph;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.util.Random;

import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartMouseEvent;
import org.jfree.chart.ChartMouseListener;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.axis.NumberTickUnit;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYItemRenderer;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see http://stackoverflow.com/questions/7231824
 * @see http://stackoverflow.com/questions/7205742
 * @see http://stackoverflow.com/questions/7208657
 * @see http://stackoverflow.com/questions/7071057
 */
public class GraphFrameOld extends JFrame {

    private static final int N = 32;
    private static final String title = "Scatter Plot Pannel";
    private static final Random rand = new Random();
    private final XYSeries added = new XYSeries("Added");

    private static XYPlot xyPlot;

    public GraphFrameOld(String s) {
        super(s);
        final ChartPanel chartPanel = createGraphPanel();

        this.add(chartPanel, BorderLayout.CENTER);
        JPanel control = new JPanel();
        control.add(new JButton(new AbstractAction("Add") {

            @Override
            public void actionPerformed(ActionEvent e) {
                for (int i = 0; i < N; i++) {
                    added.add(rand.nextDouble(), rand.nextDouble());
                }
            }
        }));

        control.add(new JButton(new AbstractAction("Test") {

            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Test");
                System.out.println(xyPlot.getDomainCrosshairValue() + " "
                        + xyPlot.getRangeCrosshairValue());

            }
        }));

        // add click event
        chartPanel.addChartMouseListener(new ChartMouseListener() {
            @Override
            public void chartMouseClicked(ChartMouseEvent e) {
                System.out.println("Click event!");
                XYPlot xyPlot2 = chartPanel.getChart().getXYPlot();
                  // Problem: the coordinates displayed are the one of the previously selected point !
                System.out.println(xyPlot2.getDomainCrosshairValue() + " "
                        + xyPlot2.getRangeCrosshairValue());
            }

            @Override
            public void chartMouseMoved(ChartMouseEvent arg0) {
            }
        });

        this.add(control, BorderLayout.SOUTH);
    }

    private ChartPanel createGraphPanel() {
        JFreeChart jfreechart = ChartFactory
                .createScatterPlot(title, "X", "Y", createSampleData(),
                        PlotOrientation.VERTICAL, true, true, false);
        xyPlot = (XYPlot) jfreechart.getPlot();
        xyPlot.setDomainCrosshairVisible(true);
        xyPlot.setRangeCrosshairVisible(true);
        XYItemRenderer renderer = xyPlot.getRenderer();
        renderer.setSeriesPaint(0, Color.blue);
        NumberAxis domain = (NumberAxis) xyPlot.getDomainAxis();
        domain.setRange(0.00, 1.00);
        domain.setTickUnit(new NumberTickUnit(0.1));
        domain.setVerticalTickLabels(true);
        NumberAxis range = (NumberAxis) xyPlot.getRangeAxis();
        range.setRange(0.0, 1.0);
        range.setTickUnit(new NumberTickUnit(0.1));
        return new ChartPanel(jfreechart);
    }

    private XYDataset createSampleData() {
        XYSeriesCollection xySeriesCollection = new XYSeriesCollection();
        XYSeries series = new XYSeries("Random");
        for (int i = 0; i < N * N; i++) {
            double x = rand.nextDouble();
            double y = rand.nextDouble();
            series.add(x, y);
        }
        xySeriesCollection.addSeries(series);
        xySeriesCollection.addSeries(added);
        return xySeriesCollection;
    }

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                GraphFrameOld demo = new GraphFrameOld(title);
                demo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                demo.pack();
                demo.setLocationRelativeTo(null);
                demo.setVisible(true);
            }
        });
    }
}

Answer 1

My guess is that your mouse listener gets called before the (internal) JFreeCharts listener is, so the cross hair point is not yet updated when your code executes (point to the previous selection still). Putting your chartMouseClicked code in an invokeLater should fix that.