如何在JFreeChart的气泡图上正确显示标签？

// 创建气泡图对象
BubbleChart bubbleChart = new BubbleChart("气泡图");

// 创建数据集对象
DefaultXYZDataset dataset = new DefaultXYZDataset();
double[][] data = { 
    { 1.0, 2.0, 3.0 }, // x坐标
    { 2.0, 3.0, 4.0 }, // y坐标
    { 100, 200, 300 } // 气泡大小
};
dataset.addSeries("series", data);

// 创建绘图对象
JFreeChart chart = ChartFactory.createBubbleChart("气泡图", "X", "Y", dataset);
XYPlot plot = (XYPlot) chart.getPlot();

// 设置渲染器对象
XYBubbleRenderer renderer = new XYBubbleRenderer();
renderer.setBaseToolTipGenerator(new StandardXYZToolTipGenerator());
renderer.setBaseItemLabelGenerator(new StandardXYZItemLabelGenerator());
renderer.setBasePositiveItemLabelPosition(new ItemLabelPosition(ItemLabelAnchor.CENTER, TextAnchor.CENTER));
renderer.setBaseItemLabelsVisible(true);
renderer.setBaseItemLabelPaint(Color.black);
renderer.setBaseItemLabelFont(new Font("SansSerif", Font.PLAIN, 9));
plot.setRenderer(renderer);

// 添加标签到气泡图上
ChartPanel chartPanel = new ChartPanel(chart);
chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));
chartPanel.getChartRenderingInfo().getPlotInfo().setDataArea(chartPanel.getChartRenderingInfo().getChartArea().clone());
int seriesIndex = 0;
for (int i = 0; i < data[0].length; i++) {
    String label = "Label " + (i+1);
    double x = data[0][i];
    double y = data[1][i];
    double size = data[2][i];
    renderer.addAnnotation(new XYTextAnnotation(label, x, y));
}

// 将气泡图添加到容器中并显示