我的使用情况可能不同于你,但值得看一下我的回答:here。

如果你对我的执行有问题,在答复中说明,你会自由地要求细节。

经过几次尝试,我决定限制图表所示<代码>LegendItem。

更改序号,在<代码>上显示 图二 我使用了梯子。 最困难的方面是在使用梯子时重新计算新图象;我不敢肯定我的解决方法是最佳的,或者说是明智的,但至少是行之有效的。

为了做到这一点,我需要聆听一系列创作(ChartChangeEventType.DATASET_UPDATED)的节目,以更新图谱,并树立精华的价值观。

因此,此法是:

public class MyExampleChartComposite extends ChartComposite {
    // snip
    /**
     * A slider to choose the legend items to display
     */
     private Slider legendSlider;
     /**
     * Number of legend items to display on the chart
     */
     private final static int NUMBER_OF_LEGENDITEMS_TO_DISPLAY = 10;

     private void createPartControl(Composite parent, int style) {
         JFreeChart chart = createChart();
         setChart(chart);
         legendSlider = new Slider(parent, SWT.NONE|SWT.H_SCROLL);
         legendSlider.addSelectionListener(new SelectionListener() {
             @Override
             public void widgetSelected(SelectionEvent arg0) {
                      refreshLegend();
             }
         });

     private JFreeChart createChart() {
         chart.addChangeListener(new ChartChangeListener() {    
             @Override
             public void chartChanged(ChartChangeEvent e) {
                  if (e.getType().equals(ChartChangeEventType.DATASET_UPDATED)) {
                      refreshLegend();
                  }
             }
         });
    }

    /**
     * Refresh the the LegendItems and the slider,
     * according to slider selection.
     */
    public void refreshLegend() {
        // Display LegendItems according to the selection
        // display the 10 nearest legend item (current selected element included)
        int begin = legendSlider.getSelection() - (NUMBER_OF_LEGENDITEMS_TO_DISPLAY/2);
        int end = legendSlider.getSelection() + (NUMBER_OF_LEGENDITEMS_TO_DISPLAY/2 -1);
        int seriesEndIndex = Math.max(getSeriesCount()-1, 0);
        // if begin is less than 0
        // set it to 0, and increase end to display 10 items
        if (begin < 0) {
            begin = 0; 
            end = NUMBER_OF_LEGENDITEMS_TO_DISPLAY - 1;
        }
        // if end is greater than the number of series plotted
        // set it to the max possible value and increase begin to
        // display 10 items
        if  (end > seriesEndIndex) {
            end = seriesEndIndex;  
            begin = seriesEndIndex - (NUMBER_OF_LEGENDITEMS_TO_DISPLAY - 1);
        }
        end = Math.min(seriesEndIndex, end);
        begin = Math.max(begin, 0);
        // Refresh only if begin != end
        if (end != begin) {
            refreshLegendItems(begin, end);
            refreshLegendSlider();
        } else {
            // in this case no more series are plotted on the chart
            // clear legend
            getChart().clearSubtitles();
        }
    }
    /**
     * Refresh the LegendTitle.
     * Display only LegendItems between beginIndex and toIndex,
     * to preserve space for the chart.
     * @param beginIndex index of the {@link LegendItemCollection} used as the beginning of the new {@link LegendTitle}
     * @param endIndex index of the {@link LegendItemCollection} used as the end of the new {@link LegendTitle}
     */
    private void refreshLegendItems(int beginIndex, int endIndex) {
        // Last 10 items
        final LegendItemCollection result = new LegendItemCollection();
        // get the renderer to retrieve legend items
        XYPlot plot = getChart().getXYPlot();
        XYItemRenderer renderer = plot.getRenderer();
        // Number of series displayed on the chart 
        // Construct the legend
        for (int i = beginIndex; i <= endIndex; i++) {
            LegendItem item = renderer.getLegendItem(0, i);
            result.add(item);
        }
        // Because the only way to create a new LegendTitle is to
        // create a LegendItemSource first
        LegendItemSource source = new LegendItemSource() {
            LegendItemCollection lic = new LegendItemCollection();
            {lic.addAll(result);}
            public LegendItemCollection getLegendItems() {  
                return lic;
            }
        };
        // clear previous legend title
        getChart().clearSubtitles();
        // Create the new LegendTitle and set its position
        LegendTitle legend = new LegendTitle(source);
        legend.setHorizontalAlignment(HorizontalAlignment.CENTER);
        legend.setVerticalAlignment(VerticalAlignment.CENTER);
        legend.setPosition(RectangleEdge.BOTTOM);
        legend.setBorder(1.0, 1.0, 1.0, 1.0);
        legend.setVisible(true);
        // Add the LegendTitle to the graph
        getChart().addLegend(legend);
    }

    /**
     * Set values of the slider according to the number of series
     * plotted on the graph
     */
    private void refreshLegendSlider() {
        int max = getSeriesCount() -1;
        int selection = Math.min(legendSlider.getSelection(), max);
        legendSlider.setValues(selection, 0, max, 1, 1, 1);
    }
}