Jfreechart与滚动条

我想在图表中添加一个滚动条，以便查看不适合屏幕的大数据集，因为要保留所有xtick。 但是，我收到以下错误消息：

Exception in thread "main" java.lang.ClassCastException: org.jfree.data.xy.XYSeriesCollection cannot be cast to org.jfree.data.category.CategoryDataset at MySlidingCategoryDatasetDemo3$DemoPanel.(MySlidingCategoryDatasetDemo3.java:86) at MySlidingCategoryDatasetDemo3.createDemoPanel(MySlidingCategoryDatasetDemo3.java:112) at MySlidingCategoryDatasetDemo3.(MySlidingCategoryDatasetDemo3.java:107) at MySlidingCategoryDatasetDemo3.main(MySlidingCategoryDatasetDemo3.java:117) 

使用以下代码：

 import java.awt.*; import javax.swing.*; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; import org.jfree.data.category.*; import org.jfree.chart.*; import org.jfree.chart.axis.NumberAxis; import org.jfree.chart.plot.PlotOrientation; import org.jfree.chart.plot.XYPlot; import org.jfree.chart.renderer.xy.StandardXYItemRenderer; import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer; import org.jfree.data.category.*; import org.jfree.data.xy.XYDataset; import org.jfree.data.xy.XYSeries; import org.jfree.data.xy.XYSeriesCollection; import org.jfree.ui.ApplicationFrame; import org.jfree.ui.RefineryUtilities; public class MySlidingCategoryDatasetDemo3 extends ApplicationFrame { static class DemoPanel extends JPanel implements ChangeListener { private static XYDataset createDataset() { XYSeries xyseries = new XYSeries("First"); xyseries.add(1.0D, 1.0D); xyseries.add(2D, 4D); xyseries.add(3D, 3D); xyseries.add(4D, 5D); xyseries.add(5D, 5D); xyseries.add(6D, 7D); xyseries.add(7D, 7D); xyseries.add(8D, 8D); xyseries.add(9D, 8D); xyseries.add(10D, 8D); xyseries.add(11D, 8D); xyseries.add(12D, 8D); xyseries.add(13D, 8D); xyseries.add(14D, 8D); xyseries.add(15D, 8D); xyseries.add(16D, 25D); xyseries.add(17D, 8D); xyseries.add(18D, 5D); xyseries.add(19D, 7D); xyseries.add(20D, 6D); xyseries.add(21D, 8D); xyseries.add(22D, 4D); xyseries.add(23D, 4D); xyseries.add(24D, 2D); xyseries.add(25D, 1.0D); XYSeriesCollection xyseriescollection = new XYSeriesCollection(); xyseriescollection.addSeries(xyseries); return xyseriescollection; } private static JFreeChart createChart(XYDataset xydataset) { JFreeChart jfreechart = ChartFactory.createXYLineChart("Line Chart Demo 2", "X", "Y", xydataset, PlotOrientation.VERTICAL, true, true, false); XYPlot xyplot = (XYPlot)jfreechart.getPlot(); xyplot.setDomainPannable(true); xyplot.setRangePannable(true); StandardXYItemRenderer xylineandshaperenderer = (StandardXYItemRenderer)xyplot.getRenderer(); xylineandshaperenderer.setBaseShapesVisible(true); xylineandshaperenderer.setBaseShapesFilled(true); NumberAxis numberaxis = (NumberAxis)xyplot.getRangeAxis(); numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits()); numberaxis.setRange(0.0D, 100D); return jfreechart; } public void stateChanged(ChangeEvent changeevent) { dataset.setFirstCategoryIndex(scroller.getValue()); } JScrollBar scroller; SlidingCategoryDataset dataset; public DemoPanel() { super(new BorderLayout()); dataset = new SlidingCategoryDataset((CategoryDataset) createDataset(), 0, 10); JFreeChart jfreechart = createChart((XYDataset) dataset); //JFreeChart jfreechart = createChart(createDataset()); ChartPanel chartpanel = new ChartPanel(jfreechart); chartpanel.setPreferredSize(new Dimension(400, 400)); scroller = new JScrollBar(0, 0, 10, 0, 50); add(chartpanel); scroller.getModel().addChangeListener(this); JPanel jpanel = new JPanel(new BorderLayout()); jpanel.add(scroller); jpanel.setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2)); jpanel.setBackground(Color.white); add(jpanel, "South"); } } public MySlidingCategoryDatasetDemo3(String s) { super(s); setDefaultCloseOperation(3); setContentPane(createDemoPanel()); } public static JPanel createDemoPanel() { return new DemoPanel(); } public static void main(String args[]) { MySlidingCategoryDatasetDemo3 slidingcategorydatasetdemo2 = new MySlidingCategoryDatasetDemo3("JFreeChart: SlidingCategoryDatasetDemo2.java"); slidingcategorydatasetdemo2.pack(); RefineryUtilities.centerFrameOnScreen(slidingcategorydatasetdemo2); slidingcategorydatasetdemo2.setVisible(true); } } 

我做错了什么？

先感谢您。

Answer 1

错误消息非常明显：

org.jfree.data.xy.XYSeriesCollection无法强制转换为org.jfree.data.category.CategoryDataset

您正在将XYSeriesCollection对象强制转换为CategoryDataset对象，该对象不起作用。 查看堆栈跟踪中的行，它由以下行引起

 dataset = new SlidingCategoryDataset((CategoryDataset) createDataset(), 0, 10); 

createDataset()方法返回XYSeriesCollection而不是CategoryDataset ，因此您无法执行此转换。 调整该方法的返回类型，或摆脱强制转换