java - JFreeChart 日期轴格式化问题

Question

我有一个时间序列图表。我将 x 轴作为日期，Y 轴只是数字。我正在尝试格式化 x 轴上的日期，但我不断收到异常。我的代码如下:

        TimeSeries trueSeries = new TimeSeries("True Data");
        TimeSeries regressionSeries = new TimeSeries("Regression Line");
        TimeSeries averageSeries = new TimeSeries("Moving Average");

        for (Date date : regression.keySet()) {
            Calendar cal = Calendar.getInstance();
            cal.setTime(date);
            int month = cal.get(Calendar.MONTH) + 1;
            int day = cal.get(Calendar.DAY_OF_MONTH);
            int year = cal.get(Calendar.YEAR);
            regressionSeries.add(new Day(day, month, year),
                    regression.get(date));
            averageSeries.add(new Day(day, month, year),
                    movingAverage.get(date));
            trueSeries.add(new Day(day, month, year), trueData.get(date));
        }
        TimeSeriesCollection dataset = new TimeSeriesCollection();
        dataset.addSeries(trueSeries);
        dataset.addSeries(regressionSeries);
        dataset.addSeries(averageSeries);
        JFreeChart chart = ChartFactory.createXYLineChart(
                stock.getCompanyName() + " (" + stock.getTicker() + ")",
                "Date", // x-axis Label
                "Close Price", // y-axis Label
                dataset, // Dataset
                PlotOrientation.VERTICAL, // Plot Orientation
                true, // Show Legend
                true, // Use tooltips
                false // Configure chart to generate URLs?
                );

然后我尝试将 x 轴转换为简单的日期格式，如下所示:

XYPlot plot = (XYPlot) chart.getPlot();
DateAxis axis = (DateAxis) plot.getDomainAxis();
axis.setDateFormatOverride(new SimpleDateFormat("dd-MM-yyyy")); 

当我运行它时，出现以下异常:

java.lang.ClassCastException: org.jfree.chart.axis.NumberAxis 无法转换为 org.jfree.chart.axis.DateAxis

有人可以告诉我我做错了什么吗？

Answer 1

根据 Adding date/time to JFreeChart graph :

"…you're using ChartFactory.createXYLineChart(), which creates a NumberAxis for the domain. Instead, use ChartFactory.createTimeSeriesChart(), which creates a DateAxis for the domain."—trashgod