scrollview、tableView Nested solutions

I found a lot on the Internet , There is no favorite scheme . It also refers to many designs , I made one that I think is relatively simple 、 The perfect solution ：

General train of thought ： Outer layer placement scrollview As a container , The upper part of the container topView, Lower part tableView. When tableView Rolling time , If topView Still in the exhibition area , Is set topView Of y coordinate , Give Way topView Move up with synchronization .

（ Be careful ： If not set tableView Of headerView,tableView、 and topView It will move up at the same time, which is not the effect I want , So set tableView Of headerView Height includes topView Height , Achieved a perfect effect , In terms of specific implementation demo）

Results the preview ：

The core code is in the parent view 、 Rolling judgment of sub attempt

// Callback of parent view scrolling , Used for horizontal scroll judgment

// Callback of parent view scrolling , Used for horizontal scroll judgment 
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
        
    CGFloat placeholderOffset = 0;
    if (self.topView.selectedIndex == 0) {
    
        if (self.firstTableView.contentOffset.y > CGRectGetHeight(self.topView.frame) - kItemheight) {
    
            placeholderOffset = CGRectGetHeight(self.topView.frame) - kItemheight;
        }else {
    
            placeholderOffset = self.firstTableView.contentOffset.y;
        }
        [self.secondTableView setContentOffset:CGPointMake(0, placeholderOffset) animated:NO];
    }else {
    
        if (self.secondTableView.contentOffset.y > CGRectGetHeight(self.topView.frame) - kItemheight) {
    
            placeholderOffset = CGRectGetHeight(self.topView.frame) - kItemheight;
        }else {
    
            placeholderOffset = self.secondTableView.contentOffset.y;
        }
        [self.firstTableView setContentOffset:CGPointMake(0, placeholderOffset) animated:NO];
    }
}

// Callback of subview scrolling , Used for rolling judgment in the vertical direction

// Callback of subview scrolling , Used for rolling judgment in the vertical direction 
- (void)updateTopViewFrame:(UIScrollView *)scrollView{
    
    CGFloat placeHolderHeight = CGRectGetHeight(self.topView.frame) - self.topView.itemHeight;
    CGFloat offsetY = scrollView.contentOffset.y;
    
    CGFloat y = 0.0;
    if (offsetY >= 0 && (offsetY <= placeHolderHeight)) {
    
        y = -offsetY;
    } else if (offsetY > placeHolderHeight) {
    
        y = -placeHolderHeight;
    } else if (offsetY < 0) {
    
        y = -offsetY;
    }
    
    [self.topView mas_updateConstraints:^(MASConstraintMaker *make) {
    
        make.top.offset(y + kNavBarHeight);
    }];
}

githut demo Download address ：https://github.com/biyuhuaping/NestScrollView