Android AChartEngine 饼图渐变效果

private void initLabelChat(View rootView) {
        NumberFormat nf = new DecimalFormat("#.# 小时");
        
        final DefaultRenderer renderer = new DefaultRenderer();
        final CategorySeries series = new CategorySeries("");

        LinearLayout layout = (LinearLayout) rootView
                .findViewById(R.id.pie_statistic_by_label);
        final GraphicalView chartView = ChartFactory.getPieChartView(
                getActivity(), series, renderer);

        chartView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SeriesSelection seriesSelection = chartView
                        .getCurrentSeriesAndPoint();
                if (seriesSelection == null) {
                    /*
                     * Toast.makeText(getActivity(),
                     * "No chart element selected", Toast.LENGTH_SHORT) .show();
                     */
                } else {
                    for (int i = 0; i < series.getItemCount(); i++) {
                        renderer.getSeriesRendererAt(i).setHighlighted(
                                i == seriesSelection.getPointIndex());
                    }
                    chartView.repaint();
                }
            }
        });

        renderer.setClickEnabled(true);
        renderer.setPanEnabled(false);
        renderer.setDisplayValues(false);

        layout.addView(chartView, new LayoutParams(700, 700));

        renderer.setZoomButtonsVisible(false);
        renderer.setZoomEnabled(false);
        renderer.setDisplayValues(true);
        renderer.setShowLegend(false);

        renderer.setLabelsTextSize(30f);
        renderer.setLabelsColor(Color.DKGRAY);
        renderer.setShowGrid(true);
        renderer.setAntialiasing(true);

        series.add("样本1", 5);

        SimpleSeriesRenderer seriesRenderer = new SimpleSeriesRenderer();
        seriesRenderer.setGradientEnabled(true);
        seriesRenderer.setChartValuesFormat(nf);
        seriesRenderer.setGradientStart(0, Color.rgb(0x04, 0xa3, 0xff));
        seriesRenderer.setGradientStop(0.8, Color.rgb(0x00, 0x89, 0xd8));
        seriesRenderer.setDisplayChartValues(false);
        renderer.addSeriesRenderer(seriesRenderer);

        series.add("样本2", 8);

        seriesRenderer = new SimpleSeriesRenderer();
        seriesRenderer.setGradientEnabled(true);
        seriesRenderer.setChartValuesFormat(nf);
        seriesRenderer.setGradientStart(0, Color.rgb(0xff, 0xb0, 0x0d));
        seriesRenderer.setGradientStop(0.8, Color.rgb(0xce, 0x97, 0x00));
        seriesRenderer.setDisplayChartValues(false);
        renderer.addSeriesRenderer(seriesRenderer);

        series.add("样本3", 6);

        seriesRenderer = new SimpleSeriesRenderer();
        seriesRenderer.setGradientEnabled(true);
        seriesRenderer.setChartValuesFormat(nf);
        seriesRenderer.setGradientStart(0, Color.rgb(0x00, 0xbc, 0x66));
        seriesRenderer.setGradientStop(0.8, Color.rgb(0x01, 0x80, 0x46));
        seriesRenderer.setDisplayChartValues(false);
        renderer.addSeriesRenderer(seriesRenderer);

        series.add("样本4", 3);

        seriesRenderer = new SimpleSeriesRenderer();
        seriesRenderer.setGradientEnabled(true);
        seriesRenderer.setChartValuesFormat(nf);
        seriesRenderer.setGradientStart(0, Color.rgb(0xff, 0x6e, 0xf6));
        seriesRenderer.setGradientStop(0.8, Color.rgb(0xff, 0x00, 0xde));
        seriesRenderer.setDisplayChartValues(false);
        renderer.addSeriesRenderer(seriesRenderer);

        chartView.repaint();
    }