@Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            return super.onFling(e1, e2, -velocityX, -velocityY);
        }
Touch Handler for preview charts. It scroll and zoom only preview area, not all preview chart data.
hellocharts-library/src/lecho/lib/hellocharts/gesture/PreviewChartTouchHandler.java