@Override
    public boolean computeScroll() {
        if (!isRotationEnabled) {
            return false;
        }
        if (scroller.computeScrollOffset()) {
            pieChart.setChartRotation(scroller.getCurrY(), false);
            // pieChart.setChartRotation() will invalidate view so no need to return true;
        }
        return false;
    }
Reference to PieChartView to use some methods specific for that kind of chart.
hellocharts-library/src/lecho/lib/hellocharts/gesture/PieChartTouchHandler.java