JFreeChart区域从图表面板的中间绘制

Question

我有一个动态面积图，我希望它从面板的中间显示，这意味着我希望数据从X轴的中间添加，而不是从图表的右侧添加。我正在使用这里显示的一个示例。如何做到这一点？这是我的代码：

public class essaijfree2 extends ApplicationFrame {
private static final String TITLE = "Dynamic Series";
private static final String START = "Start";
private static final String STOP = "Stop";
private static final float MINMAX = 100;
private static final int COUNT = 2 * 60;
private static final int FAST = 100;
private static final int SLOW = FAST * 5;
private static final Random random = new Random();
private Timer timer;
public essaijfree2(final String title) {
    super(title);
    final DynamicTimeSeriesCollection dataset =
        new DynamicTimeSeriesCollection(1, COUNT, new Second());
    dataset.setTimeBase(new Second(0, 0, 0, 1, 1, 2011));
    dataset.addSeries(gaussianData(), 0, "Gaussian data");
    JFreeChart chart = createChart(dataset);
    XYPlot xyPlot = (XYPlot) chart.getPlot();
    XYDifferenceRenderer r = new XYDifferenceRenderer(Color.green,Color.red, true);
    xyPlot.setRenderer(r);

    final JComboBox combo = new JComboBox();
    combo.addItem("Fast");
    combo.addItem("Slow");
    combo.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if ("Fast".equals(combo.getSelectedItem())) {
                timer.setDelay(FAST);
            } else {
                timer.setDelay(SLOW);
            }
        }
    });
    this.add(new ChartPanel(chart), BorderLayout.CENTER);
    JPanel btnPanel = new JPanel(new FlowLayout());
    btnPanel.add(combo);
    this.add(btnPanel, BorderLayout.SOUTH);
    timer = new Timer(FAST, new ActionListener() {
        float[] newData = new float[1];
        @Override
        public void actionPerformed(ActionEvent e) {
            newData[0] = randomValue();
            dataset.advanceTime();
            dataset.appendData(newData);
        }
    });
}
private float randomValue() {
    return (float) (random.nextGaussian() * MINMAX / 3);
}
private float[] gaussianData() {
    float[] a = new float[COUNT];
    for (int i = 0; i < a.length; i++) {
        a[i] = randomValue();
    }
    return a;
}
private JFreeChart createChart(final XYDataset dataset) {
    final JFreeChart result = ChartFactory.createXYAreaChart(
        TITLE, "hh:mm:ss", "milliVolts", dataset,PlotOrientation.VERTICAL, true, true, false);
    final XYPlot plot = result.getXYPlot();
    ValueAxis domain = plot.getDomainAxis();
    domain.setAutoRange(true);
    ValueAxis range = plot.getRangeAxis();
    range.setRange(-MINMAX, MINMAX);
    return result;
}
public void start() {
    timer.start();
}
public static void main(final String[] args) {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            essaijfree2 demo = new essaijfree2(TITLE);
            demo.pack();
            RefineryUtilities.centerFrameOnScreen(demo);
            demo.setVisible(true);
            demo.start();
        }
    });
}

Answer 1

设置域轴上的上边距：

domain.setUpperMargin(0.5);