java - Display mouse coordinates near mouse as hints on mouse move

Question

On an XYPlot, I want the coordinates of mouse displayed as hint near to mouse, but only when (the mouse) move on chart! In another words, when the crosshair moves to another point, the positioning of the coordinate values would move too, following the crosshair.

Also 1 horizontal line and 1 vertical line will be drawn, that intersects specifically at the point that mouse is over on.

Is this possible? Until now I can get the coordinates and printed on console using ChartMouseListener and chartMouseMoved method.

This is my project and how I want to be the chart with mouse.

Answer 1

JFreeChart has quite flexible support for crosshairs. To do what you described I would use an Overlay on the ChartPanel, and update the crosshairs from your ChartMouseListener. Here is a self-contained example (which I'll add to the collection of demos that we ship with the JFreeChart Developer Guide):

package org.jfree.chart.demo;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.geom.Rectangle2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
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.ValueAxis;
import org.jfree.chart.panel.CrosshairOverlay;
import org.jfree.chart.plot.Crosshair;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.general.DatasetUtilities;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;
import org.jfree.ui.RectangleEdge;

/**
 * A demo showing crosshairs that follow the data points on an XYPlot.
 */
public class CrosshairOverlayDemo1 extends JFrame implements ChartMouseListener {

    private ChartPanel chartPanel;

    private Crosshair xCrosshair;

    private Crosshair yCrosshair;

    public CrosshairOverlayDemo1(String title) {
        super(title);
        setContentPane(createContent());
    }

    private JPanel createContent() {
        JFreeChart chart = createChart(createDataset());
        this.chartPanel = new ChartPanel(chart);
        this.chartPanel.addChartMouseListener(this);
        CrosshairOverlay crosshairOverlay = new CrosshairOverlay();
        this.xCrosshair = new Crosshair(Double.NaN, Color.GRAY, new BasicStroke(0f));
        this.xCrosshair.setLabelVisible(true);
        this.yCrosshair = new Crosshair(Double.NaN, Color.GRAY, new BasicStroke(0f));
        this.yCrosshair.setLabelVisible(true);
        crosshairOverlay.addDomainCrosshair(xCrosshair);
        crosshairOverlay.addRangeCrosshair(yCrosshair);
        chartPanel.addOverlay(crosshairOverlay);
        return chartPanel;
    }

    private JFreeChart createChart(XYDataset dataset) {
        JFreeChart chart = ChartFactory.createXYLineChart("Crosshair Demo", 
                "X", "Y", dataset);
        return chart;
    }

    private XYDataset createDataset() {
        XYSeries series = new XYSeries("S1");
        for (int x = 0; x < 10; x++) {
            series.add(x, x + Math.random() * 4.0);
        }
        XYSeriesCollection dataset = new XYSeriesCollection(series);
        return dataset;
    }

    @Override
    public void chartMouseClicked(ChartMouseEvent event) {
        // ignore
    }

    @Override
    public void chartMouseMoved(ChartMouseEvent event) {
        Rectangle2D dataArea = this.chartPanel.getScreenDataArea();
        JFreeChart chart = event.getChart();
        XYPlot plot = (XYPlot) chart.getPlot();
        ValueAxis xAxis = plot.getDomainAxis();
        double x = xAxis.java2DToValue(event.getTrigger().getX(), dataArea, 
                RectangleEdge.BOTTOM);
        double y = DatasetUtilities.findYValue(plot.getDataset(), 0, x);
        this.xCrosshair.setValue(x);
        this.yCrosshair.setValue(y);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                CrosshairOverlayDemo1 app = new CrosshairOverlayDemo1(
                        "JFreeChart: CrosshairOverlayDemo1.java");
                app.pack();
                app.setVisible(true);
            }
        });
    }

}