直播卖货小程序源码中，商品分类页面是如何实现的

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    if (indexPath.row != selectTableIndex) {
        //判断滑动是不是因为点击一级分类引起
        isClickLeft = YES;
        selectTableIndex = indexPath.row;
        [tableView reloadData];
  //二级分类滑动到对应的区域
        [_classCollectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:selectTableIndex] atScrollPosition:UICollectionViewScrollPositionTop animated:YES];
        ///让collectionview的滑动回退sectionheader的高度
        _classCollectionView.contentOffset = CGPointMake(0, _classCollectionView.contentOffset.y-70);
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            isClickLeft = NO;
        });
    }
}

///collectionview将要加载头尾视图调用的方法
- (void)collectionView:(UICollectionView *)collectionView willDisplaySupplementaryView:(UICollectionReusableView *)view forElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath {
    if (isClickLeft) {
        return;
    }
 CGPoint point = [view convertPoint:CGPointZero toView:self.view];
    ///判断是不是SectionHeader
    if (point.y < 100 && [elementKind isEqualToString:UICollectionElementKindSectionHeader]) {
        ///更新当前选中的一级分类的indexpath
        selectTableIndex = indexPath.section;
        [_classTableView reloadData];
    }
}
///collectionview已经加载完头尾视图调用的方法
- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingSupplementaryView:(UICollectionReusableView *)view forElementOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath {
    if (isClickLeft) {
        return;
    }
 CGPoint point = [view convertPoint:CGPointZero toView:self.view];
    ///判断是不是SectionHeader
    if (point.y < 100 && [elementKind isEqualToString:UICollectionElementKindSectionHeader]) {
        ///更新当前选中的一级分类的indexpath
        selectTableIndex = indexPath.section;
        [_classTableView reloadData];
}