JFreeChart简单图（抛物线）

我用JFreeChart写了一个简单的抛物线图。

package parabolademo; import java.awt.geom.Point2D; import java.awt.geom.Rectangle2D; 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.plot.PlotOrientation; import org.jfree.chart.plot.XYPlot; import org.jfree.data.function.Function2D; import org.jfree.data.function.PolynomialFunction2D; import org.jfree.data.general.DatasetUtilities; import org.jfree.data.xy.XYDataset; import org.jfree.ui.ApplicationFrame; import org.jfree.ui.RefineryUtilities; public class ParabolaDemo extends ApplicationFrame { /* * @param title the frame title. */ public ParabolaDemo(final String title) { super(title); double[] a = {0.0, 0.0, 3.0}; Function2D p = new PolynomialFunction2D(a); XYDataset dataset = DatasetUtilities.sampleFunction2D(p, -20.0, 20.0, 100, "Function"); final JFreeChart chart = ChartFactory.createXYLineChart( "Parabola", "X", "Y", dataset, PlotOrientation.VERTICAL, true, true, false ); final ChartPanel chartPanel = new ChartPanel(chart); chartPanel.addChartMouseListener(new ChartMouseListener() { @Override public void chartMouseClicked(ChartMouseEvent cme) { Point2D po = chartPanel.translateScreenToJava2D(cme.getTrigger().getPoint()); Rectangle2D plotArea = chartPanel.getScreenDataArea(); XYPlot plot = (XYPlot) chart.getPlot(); // your plot double chartX = plot.getDomainAxis().java2DToValue(po.getX(), plotArea, plot.getDomainAxisEdge()); double chartY = plot.getRangeAxis().java2DToValue(po.getY(), plotArea, plot.getRangeAxisEdge()); System.out.println("Clicked!"); System.out.println("X:" + chartX + ", Y:" + chartY); } @Override public void chartMouseMoved(ChartMouseEvent cme) { } }); chartPanel.setPreferredSize(new java.awt.Dimension(500, 270)); setContentPane(chartPanel); } public static void main(final String[] args) { final ParabolaDemo demo = new ParabolaDemo("Parabola Plot Demo"); demo.pack(); RefineryUtilities.centerFrameOnScreen(demo); demo.setVisible(true); } 

}

如何获取FUNCTION PLOT点的坐标（我的chartMouseListener获取窗口中任意点的坐标）？ 用户移动鼠标并释放鼠标按钮后如何接收点坐标？ 我希望在单击鼠标时，绘图的点跟随鼠标，因此将重建绘图（为此目的，需要再次计算系数，知道此坐标并采用任何其他2个坐标）。 怎么做？ 如何用新系数重建情节？

Answer 1

给定名为cmd的ChartMouseEvent ，忽略除XYItemEntity之外的任何类型的实体。 一旦你知道了实体，就不要插值 – 只是查询数据集。

 ChartEntity ce = cme.getEntity(); if (ce instanceof XYItemEntity) { XYItemEntity e = (XYItemEntity) ce; XYDataset d = e.getDataset(); int s = e.getSeriesIndex(); int i = e.getItem(); System.out.println("X:" + d.getX(s, i) + ", Y:" + d.getY(s, i)); } 

还要考虑在绘图的渲染器上调用setBaseShapesVisible(true) 。