JFreeChart getRenderer返回null

Question

我试图根据点击图例项目设置一个可见或不可见的系列;但plot.getRenderer()会返回null，因此我无法设置系列可见性。这是代码：

private void legendMouseClick(ChartMouseEvent event) {
    ChartEntity entity = event.getEntity();
    if (entity instanceof LegendItemEntity) {
        //*
        LegendItemEntity itemEntity = (LegendItemEntity) entity;
        XYDataset dataset = (XYDataset) itemEntity.getDataset();
        int index = dataset.indexOf(itemEntity.getSeriesKey());
        CombinedDomainXYPlot plot = (CombinedDomainXYPlot) event.getChart().getPlot();
        XYItemRenderer renderer = plot.getRenderer(); //renderer is null

        if (renderer == null) {
          return;
        }
        System.out.println("Renderer count: " + plot.getRendererCount());
        renderer.setSeriesVisible(index, !renderer.isSeriesVisible(index), false);
    }
}

感谢您的帮助