Question

我正在尝试运行以下代码，它会在getSeriesVisible上抛出异常：

    chart.addChangeListener(new ChartChangeListener() {

        int indexChanged = -1;

        @Override
        public void chartChanged(ChartChangeEvent event) {
            XYPlot ff = chart.getXYPlot();
            XYItemRenderer y = ff.getRenderer();
            boolean b = y.getSeriesVisible(0);
           // chart.getXYPlot().getRenderer().setSeriesVisible(0, b);
        }
    });

消息：线程“AWT-EventQueue-0”中的异常java.lang.NullPointerException

任何想法？

更新：我正在添加几个系列并生成图表如下：

    XYSeriesCollection data = new XYSeriesCollection();
    XYSeries series = new XYSeries("Series 1", true);
    series.add(1, 2);
    series.add(3, 5);
    series.add(8, 10);
    series.add(11, 3);
    series.add(8, 10);
    data.addSeries(series);

    series = new XYSeries("Series 2");
    series.add(5, -2);
    series.add(7, 6);
    series.add(8, 12);
    series.add(11, -2);
    series.add(15, 10);
    data.addSeries(series);

    final JFreeChart chart = ChartFactory.createXYLineChart("Chart", "X", "Y", data, PlotOrientation.VERTICAL, true, true, false);

Answer 1

它必须位于代码中的其他位置。我在下面使用修改后的addButton()监听器看到了此example的预期结果。

addButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        int n = dataset.getSeriesCount();
        dataset.addSeries("Series" + n, createSeries(n));
        XYPlot plot = chart.getXYPlot();
        XYItemRenderer renderer = plot.getRenderer();
        System.out.println(renderer.isSeriesVisible(n));
    }
});

JFreeChart在getSeriesVisible上抛出异常

1 个答案: