docs: public int getCurrentPage() {
          int currentPage = 1;
          int count = mScrollable.getScrollingItemsCount();
          if (mSupportScrollByPage && mCurrentItemIndex >= 0 &&
                  mCurrentItemIndex < count) {
              currentPage = (Math.min(mCurrentItemIndex + mPageSize - 1, count - 1)/mPageSize);
          }
          return currentPage;
      }