java - 如何使用 JFreeChart 获取鼠标单击时的点坐标？

Question

我正在尝试获取在散点图上用鼠标单击的点的坐标。

当你点击一个点时，“点击事件!”并且坐标打印在控制台上。当您单击“测试”按钮时，“测试”和坐标会打印在控制台上。

问题:点击按钮后打印的坐标是最新的。单击某个点后打印的坐标是先前选择的点。

我该如何解决这个问题(所以当我点击一个点时，会显示新选择点的坐标)？

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

我的猜测是您的鼠标监听器在(内部)JFreeCharts 监听器之前被调用，因此当您的代码执行时十字准线点尚未更新(仍指向之前的选择)。将您的 chartMouseClicked 代码放入 invokeLater 应该可以解决这个问题。