封装了一个顺滑嵌套滚动的框架

首先查看效果图

就是开始滚动的时候，上面的头部和下面的内容是
一起滚动的，但是当滚动到segment 的时候，segment
是悬停 的，下面的tableView是分区的

架构设计

我们设计一个架构，以下面的tablView为主体，上面的内容放在tablView 的contentInset.top范围内，当上滑滚动的时候，如果滑动距离超过了segment的位置，则将segment放在tableView的父视图上，这样达到了一个悬停的效果，看上去是悬停了，其实是segment的父视图从tableView 变成了tableView的父视图，下拉的时候同样如此，当下拉达到临界便宜量的时候，segment的就从tableView的父视图变成了tablView，这样就跟着tableView滚动了，达到了顺畅嵌套滚动的效果

代码

`
@interface LBPageSmoothView()

@property (nonatomic, weak) id dataSource;
@property (nonatomic, strong) GKPageSmoothCollectionView *listCollectionView;
@property (nonatomic, strong) NSMutableDictionary *listDict;
@property (nonatomic, strong) NSMutableDictionary *listHeaderDict;

@property (nonatomic, assign) LBPageSmoothHoverType hoverType;

@property (nonatomic, strong) UIView *headerContainerView;
@property (nonatomic, weak) UIView *headerView;
@property (nonatomic, weak) UIView *segmentedView;
@property (nonatomic, weak) UIScrollView *currentListScrollView;

@property (nonatomic, strong) UIView *bottomContainerView;

@property (nonatomic, assign) BOOL syncListContentOffsetEnabled;
@property (nonatomic, assign) CGFloat currentHeaderContainerViewY;

@property (nonatomic, assign) CGFloat headerContainerHeight;
@property (nonatomic, assign) CGFloat headerHeight;
@property (nonatomic, assign) CGFloat segmentedHeight;
@property (nonatomic, assign) CGFloat currentListInitializeContentOffsetY;

@property (nonatomic, assign) NSInteger currentIndex;

@property (nonatomic, assign) BOOL isLoaded;

@property (nonatomic, strong) UIPanGestureRecognizer *panGesture;

@property (nonatomic, weak) UIScrollView *scrollView;
@property (nonatomic, assign) BOOL isDragScrollView;
@property (nonatomic, assign) CGFloat lastTransitionY;
@property (nonatomic, assign) BOOL isOnTop;

@property (nonatomic, assign) CGFloat currentListPanBeganContentOffsetY;
@property (nonatomic, assign) BOOL originBounces;
@property (nonatomic, assign) BOOL originShowsVerticalScrollIndicator;

@end

@implementation LBPageSmoothView

• (instancetype)initWithDataSource:(id)dataSource {
  if (self = [super initWithFrame:CGRectZero]) {
  self.dataSource = dataSource;
  _listDict = [NSMutableDictionary dictionary];
  _listHeaderDict = [NSMutableDictionary dictionary];
  _ceilPointHeight = 0;

    [self addSubview:self.listCollectionView];
    [self addSubview:self.headerContainerView];
    [self refreshHeaderView];
  

  }
  return self;
  }

• (void)dealloc {
  for (id listItem in self.listDict.allValues) {
  [listItem.listScrollView removeObserver:self forKeyPath:@“contentOffset”];
  }
  }

• (void)layoutSubviews {
  [super layoutSubviews];

  if (self.listCollectionView.superview == self) {
  self.listCollectionView.frame = self.bounds;
  }else {
  CGRect frame = self.listCollectionView.frame;
  frame.origin.y = self.segmentedHeight;
  frame.size.height = self.bottomContainerView.frame.size.height - self.segmentedHeight;
  self.listCollectionView.frame = frame;
  }
  }

• (void)refreshHeaderView {
  [self loadHeaderAndSegmentedView];

  __weak __typeof(self) weakSelf = self;
  [self refreshWidthCompletion:^(CGSize size) {
  __strong __typeof(weakSelf) self = weakSelf;
  CGRect frame = self.headerContainerView.frame;
  if (CGRectEqualToRect(frame, CGRectZero)) {
  frame = CGRectMake(0, 0, size.width, self.headerContainerHeight);
  }else {
  frame.size.height = self.headerContainerHeight;
  }
  self.headerContainerView.frame = frame;

    self.headerView.frame = CGRectMake(0, 0, size.width, self.headerHeight);
    self.segmentedView.frame =  CGRectMake(0, self.headerHeight, size.width, self.segmentedHeight);
    
    for (id list in self.listDict.allValues) {
        list.listScrollView.contentInset = UIEdgeInsetsMake(self.headerContainerHeight, 0, 0, 0);
    }
    
    if (self.isBottomHover) {
        self.bottomContainerView.frame = CGRectMake(0, size.height - self.segmentedHeight, size.width, size.height - self.ceilPointHeight);
        
        if (self.headerHeight > size.height) {
            self.segmentedView.frame = CGRectMake(0, 0, size.width, self.segmentedHeight);
            [self.bottomContainerView addSubview:self.segmentedView];
        }
    }
  

  }];
  }

• (void)updateSegmentHeight:(CGFloat)height
  {
  CGFloat offset = height - self.segmentedHeight;
  self.segmentedHeight = height;
  self.headerContainerHeight = self.headerHeight + self.segmentedHeight;
  for (id list in self.listDict.allValues) {
  CGFloat currentOffset = list.listScrollView.contentOffset.y;
  list.listScrollView.contentInset = UIEdgeInsetsMake(self.headerContainerHeight, 0, 0, 0);
  CGPoint tooffset = CGPointMake(0, currentOffset - offset);
  list.listScrollView.contentOffset = tooffset;
  }

  self.segmentedView.frame = CGRectMake(CGRectGetMinX(self.segmentedView.frame), CGRectGetMinY(self.segmentedView.frame), CGRectGetWidth(self.segmentedView.frame), height);

  self.headerContainerView.frame = CGRectMake(CGRectGetMinX(self.headerContainerView.frame), CGRectGetMinY(self.headerContainerView.frame), CGRectGetWidth(self.headerContainerView.frame), self.headerContainerHeight);
  for (UIView *listHeaderView in self.listHeaderDict.allValues) {
  listHeaderView.frame = CGRectMake(0, -self.headerContainerHeight, self.bounds.size.width, self.headerContainerHeight);
  }
  }

• (void)reloadData {
  self.currentListScrollView = nil;
  self.currentIndex = self.defaultSelectedIndex;
  self.syncListContentOffsetEnabled = NO;
  self.currentHeaderContainerViewY = 0;
  self.isLoaded = YES;

  [self.listHeaderDict removeAllObjects];

  for (id list in self.listDict.allValues) {
  [list.listScrollView removeObserver:self forKeyPath:@“contentOffset”];
  [list.listView removeFromSuperview];
  }
  [_listDict removeAllObjects];

  __weak __typeof(self) weakSelf = self;
  [self refreshWidthCompletion:^(CGSize size) {
  __strong __typeof(weakSelf) self = weakSelf;
  [self.listCollectionView setContentOffset:CGPointMake(size.width * self.currentIndex, 0) animated:NO];
  [self.listCollectionView reloadData];
  }];
  }

• (void)scrollToOriginalPoint {
  [self.currentListScrollView setContentOffset:CGPointMake(0, -self.headerContainerHeight) animated:YES];
  }

• (void)scrollToCriticalPoint {
  [self.currentListScrollView setContentOffset:CGPointMake(0, -(self.segmentedHeight+self.ceilPointHeight)) animated:YES];
  }

• (void)showingOnTop {
  if (self.bottomContainerView.isHidden) return;
  [self dragBegan];
  [self dragShowing];
  }

• (void)showingOnBottom {
  if (self.bottomContainerView.isHidden) return;
  [self dragDismiss];
  }

• (void)setBottomHover:(BOOL)bottomHover {
  _bottomHover = bottomHover;

  if (bottomHover) {
  __weak __typeof(self) weakSelf = self;
  [self refreshWidthCompletion:^(CGSize size) {
  __strong __typeof(weakSelf) self = weakSelf;
  self.bottomContainerView.frame = CGRectMake(0, size.height - self.segmentedHeight, size.width, size.height - self.ceilPointHeight);
  [self addSubview:self.bottomContainerView];

        if (self.headerHeight > size.height) {
            self.segmentedView.frame = CGRectMake(0, 0, size.width, self.segmentedHeight);
            [self.bottomContainerView addSubview:self.segmentedView];
        }
    }];
  

  }else {
  [self.bottomContainerView removeFromSuperview];
  }
  }

• (void)setAllowDragBottom:(BOOL)allowDragBottom {
  _allowDragBottom = allowDragBottom;

  if (self.bottomHover) {
  if (allowDragBottom) {
  [self.bottomContainerView addGestureRecognizer:self.panGesture];
  }else {
  [self.bottomContainerView removeGestureRecognizer:self.panGesture];
  }
  }
  }

#pragma mark - UICollectionViewDataSource

• (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
  return self.isLoaded ? 1 : 0;
  }

• (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
  return [self.dataSource numberOfListsInSmoothView:self];
  }

• (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:GKPageSmoothViewCellID forIndexPath:indexPath];
  id list = self.listDict[@(indexPath.item)];
  if (list == nil) {
  list = [self.dataSource smoothView:self initListAtIndex:indexPath.item];
  _listDict[@(indexPath.item)] = list;
  [list.listView setNeedsLayout];
  [list.listView layoutIfNeeded];

    UIScrollView *listScrollView = list.listScrollView;
    if ([listScrollView isKindOfClass:[UITableView class]]) {
        ((UITableView *)listScrollView).estimatedRowHeight = 0;
        ((UITableView *)listScrollView).estimatedSectionHeaderHeight = 0;
        ((UITableView *)listScrollView).estimatedSectionFooterHeight = 0;
    }
    if (@available(iOS 11.0, *)) {
        listScrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    }
    
    if (CGSizeEqualToSize(listScrollView.contentSize, CGSizeZero)) {
        listScrollView.contentSize = CGSizeMake(listScrollView.contentSize.width, self.bounds.size.height);
    }
    
    if (!self.isOnTop) {
        listScrollView.contentInset = UIEdgeInsetsMake(self.headerContainerHeight, 0, self.bottomInset, 0);
        self.currentListInitializeContentOffsetY = -listScrollView.contentInset.top + MIN(-self.currentHeaderContainerViewY, (self.headerHeight - self.ceilPointHeight));
        listScrollView.contentOffset = CGPointMake(0, self.currentListInitializeContentOffsetY);
    }
    UIView *listHeader = [[UIView alloc] initWithFrame:CGRectMake(0, -self.headerContainerHeight, self.bounds.size.width, self.headerContainerHeight)];
    [listScrollView addSubview:listHeader];
    
    if (!self.isOnTop && self.headerContainerView.superview == nil) {
        [listHeader addSubview:self.headerContainerView];
    }
    self.listHeaderDict[@(indexPath.item)] = listHeader;
    [listScrollView addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
    // bug fix #69 修复首次进入时可能出现的headerView无法下拉的问题
    [listScrollView setContentOffset:listScrollView.contentOffset];
  

  }
  for (id listItem in self.listDict.allValues) {
  listItem.listScrollView.scrollsToTop = (listItem == list);
  }

  UIView *listView = list.listView;
  if (listView != nil && listView.superview != cell.contentView) {
  for (UIView *view in cell.contentView.subviews) {
  [view removeFromSuperview];
  }
  listView.frame = cell.contentView.bounds;
  [cell.contentView addSubview:listView];
  }
  return cell;
  }

• (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
  return self.listCollectionView.bounds.size;
  }

• (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
  [self listDidAppear:indexPath.item];
  }

• (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
  [self listDidDisappear:indexPath.item];
  }

• (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
  self.panGesture.enabled = NO;
  }

• (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  if ([self.delegate respondsToSelector:@selector(smoothView:scrollViewDidScroll:)]) {
  [self.delegate smoothView:self scrollViewDidScroll:scrollView];
  }

  NSInteger index = scrollView.contentOffset.x / scrollView.bounds.size.width;

  NSInteger ratio = (int)scrollView.contentOffset.x % (int)scrollView.bounds.size.width;

  if (!self.isOnTop) {
  UIScrollView *listScrollView = self.listDict[@(index)].listScrollView;
  if (index != self.currentIndex && ratio == 0 && !(scrollView.isDragging || scrollView.isDecelerating) && listScrollView.contentOffset.y <= -(self.segmentedHeight + self.ceilPointHeight)) {
  [self horizontalScrollDidEndAtIndex:index];
  }else {
  // 左右滚动的时候，把headerContainerView添加到self，达到悬浮的效果
  if (self.headerContainerView.superview != self) {
  CGRect frame = self.headerContainerView.frame;
  frame.origin.y = self.currentHeaderContainerViewY;
  self.headerContainerView.frame = frame;
  [self addSubview:self.headerContainerView];
  }
  }
  }

  if (index != self.currentIndex && ratio == 0) {
  self.currentIndex = index;
  }
  }

• (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
  if (!decelerate) {
  NSInteger index = scrollView.contentOffset.x / scrollView.bounds.size.width;
  [self horizontalScrollDidEndAtIndex:index];
  }
  self.panGesture.enabled = YES;
  }

• (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  NSInteger index = scrollView.contentOffset.x / scrollView.bounds.size.width;
  [self horizontalScrollDidEndAtIndex:index];
  self.panGesture.enabled = YES;
  }

• (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
  // 修复快速闪烁问题
  self.currentIndex = scrollView.contentOffset.x / scrollView.bounds.size.width;
  self.currentListScrollView = self.listDict[@(self.currentIndex)].listScrollView;
  }

#pragma mark - KVO

• (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
  if ([keyPath isEqualToString:@“contentOffset”]) {
  UIScrollView *scrollView = (UIScrollView *)object;
  if (scrollView != nil) {
  [self listScrollViewDidScroll:scrollView];
  }
  }else {
  [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
  }
  }

#pragma mark - Gesture

• (void)handlePanGesture:(UIPanGestureRecognizer *)panGesture {
  if (panGesture.state == UIGestureRecognizerStateBegan) {
  if ([self.delegate respondsToSelector:@selector(smoothViewDragBegan:)]) {
  [self.delegate smoothViewDragBegan:self];
  }
  [self dragBegan];

    // 记录scrollView的某些属性
    self.originBounces = self.scrollView.bounces;
    self.originShowsVerticalScrollIndicator = self.scrollView.showsVerticalScrollIndicator;
    
    // bug fix #47，当UIScrollView向下滚动的时候，向下拖拽完成手势操作导致的错乱问题
    if (self.currentListScrollView.isDecelerating) {
        [self.currentListScrollView setContentOffset:self.currentListScrollView.contentOffset animated:NO];
    }
  

  }

  CGPoint translation = [panGesture translationInView:self.bottomContainerView];
  if (self.isDragScrollView) {
  [self allowScrolling:self.scrollView];
  // 当UIScrollView在最顶部时，处理视图的滑动
  if (self.scrollView.contentOffset.y <= 0) {
  if (translation.y > 0) { // 向下拖拽
  [self forbidScrolling:self.scrollView];
  self.isDragScrollView = NO;

            CGRect frame = self.bottomContainerView.frame;
            frame.origin.y += translation.y;
            self.bottomContainerView.frame = frame;
            
            if (!self.isAllowDragScroll) {
                self.scrollView.panGestureRecognizer.enabled = NO;
                self.scrollView.panGestureRecognizer.enabled = YES;
            }
        }
    }
  

  }else {
  CGFloat offsetY = self.scrollView.contentOffset.y;
  CGFloat ceilPointY = self.ceilPointHeight;

    if (offsetY <= 0) {
        [self forbidScrolling:self.scrollView];
        if (translation.y > 0) { // 向下拖拽
            CGRect frame = self.bottomContainerView.frame;
            frame.origin.y += translation.y;
            self.bottomContainerView.frame = frame;
        }else if (translation.y < 0 && self.bottomContainerView.frame.origin.y > ceilPointY) { // 向上拖拽
            CGRect frame = self.bottomContainerView.frame;
            frame.origin.y = MAX((self.bottomContainerView.frame.origin.y + translation.y), ceilPointY);
            self.bottomContainerView.frame = frame;
        }
    }else {
        if (translation.y < 0 && self.bottomContainerView.frame.origin.y > ceilPointY) {
            CGRect frame = self.bottomContainerView.frame;
            frame.origin.y = MAX((self.bottomContainerView.frame.origin.y + translation.y), ceilPointY);
            self.bottomContainerView.frame = frame;
        }
        
        if (self.bottomContainerView.frame.origin.y > ceilPointY) {
            [self forbidScrolling:self.scrollView];
        }else {
            [self allowScrolling:self.scrollView];
        }
    }
  

  }

  if (panGesture.state == UIGestureRecognizerStateEnded) {
  CGPoint velocity = [panGesture velocityInView:self.bottomContainerView];
  if (velocity.y < 0) { // 上滑
  if (fabs(self.lastTransitionY) > 5 && self.isDragScrollView == NO) {
  [self dragShowing];
  }else {
  if (self.bottomContainerView.frame.origin.y > (self.ceilPointHeight + self.bottomContainerView.frame.size.height / 2)) {
  [self dragDismiss];
  }else {
  [self dragShowing];
  }
  }
  }else { // 下滑
  if (fabs(self.lastTransitionY) > 5 && self.isDragScrollView == NO && !self.scrollView.isDecelerating) {
  [self dragDismiss];
  }else {
  if (self.bottomContainerView.frame.origin.y > (self.ceilPointHeight + self.bottomContainerView.frame.size.height / 2)) {
  [self dragDismiss];
  }else {
  [self dragShowing];
  }
  }
  }

    [self allowScrolling:self.scrollView];
    self.isDragScrollView = NO;
    self.scrollView = nil;
  

  }

  [panGesture setTranslation:CGPointZero inView:self.bottomContainerView];
  self.lastTransitionY = translation.y;
  }

#pragma mark - UIGestureRecognizerDelegate

• (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
  if (gestureRecognizer == self.panGesture) {
  UIView *touchView = touch.view;
  while (touchView != nil) {
  if (touchView == self.currentListScrollView) {
  self.scrollView = (UIScrollView *)touchView;
  self.isDragScrollView = YES;
  break;
  }else if (touchView == self.bottomContainerView) {
  self.isDragScrollView = NO;
  break;
  }
  touchView = (UIView *)[touchView nextResponder];
  }
  }
  return YES;
  }

• (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gestureRecognizer {
  // 左右滑动时禁止上下滑动
  CGPoint transition = [gestureRecognizer translationInView:gestureRecognizer.view];
  if (transition.x != 0) return NO;
  return YES;
  }

• (BOOL)gestureRecognizer:(UIPanGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
  if (gestureRecognizer == self.panGesture) {
  if (otherGestureRecognizer == self.scrollView.panGestureRecognizer) {
  return YES;
  }
  }
  return NO;
  }

#pragma mark - Private Methods

• (void)listScrollViewDidScroll:(UIScrollView *)scrollView {
  if (self.listCollectionView.isDragging || self.listCollectionView.isDecelerating) return;

  if (self.isOnTop) { // 在顶部时无需处理headerView
  // 取消scrollView下滑时的弹性效果
  // buf fix #47，iOS12及以下系统isDragging会出现不准确的情况，所以这里改为用isTracking判断
  if (self.isAllowDragScroll && (scrollView.isTracking || scrollView.isDecelerating)) {
  if (scrollView.contentOffset.y < 0) {
  scrollView.contentOffset = CGPointZero;
  }
  }

    if ([self.delegate respondsToSelector:@selector(smoothView:listScrollViewDidScroll:contentOffset:)]) {
        [self.delegate smoothView:self listScrollViewDidScroll:scrollView contentOffset:scrollView.contentOffset];
    }
  

  }else { // 不在顶部，通过列表scrollView滑动确定悬浮位置
  NSInteger listIndex = [self listIndexForListScrollView:scrollView];
  if (listIndex != self.currentIndex) return;
  self.currentListScrollView = scrollView;
  CGFloat contentOffsetY = scrollView.contentOffset.y + self.headerContainerHeight;

    if (contentOffsetY < (self.headerHeight - self.ceilPointHeight)) {
        self.hoverType = LBPageSmoothHoverTypeNone;
        self.syncListContentOffsetEnabled = YES;
        self.currentHeaderContainerViewY = -contentOffsetY;
        for (id list in self.listDict.allValues) {
            if (list.listScrollView != scrollView) {
                [list.listScrollView setContentOffset:scrollView.contentOffset animated:NO];
            }
        }
        UIView *listHeader = [self listHeaderForListScrollView:scrollView];
        if (self.headerContainerView.superview != listHeader) {
            CGRect frame = self.headerContainerView.frame;
            frame.origin.y = 0;
            self.headerContainerView.frame = frame;
            [listHeader addSubview:self.headerContainerView];
        }
        
        if (self.isControlVerticalIndicator && self.ceilPointHeight != 0) {
            self.currentListScrollView.showsVerticalScrollIndicator = NO;
        }
        
        if (self.isBottomHover) {
            if (contentOffsetY < (self.headerContainerHeight - self.frame.size.height)) {
                self.hoverType = LBPageSmoothHoverTypeBottom;
                if (self.segmentedView.superview != self.bottomContainerView) {
                    self.bottomContainerView.hidden = NO;
                    CGRect frame = self.segmentedView.frame;
                    frame.origin.y = 0;
                    self.segmentedView.frame = frame;
                    [self.bottomContainerView addSubview:self.segmentedView];
                }
            }else {
                if (self.segmentedView.superview != self.headerContainerView) {
                    self.bottomContainerView.hidden = YES;
                    CGRect frame = self.segmentedView.frame;
                    frame.origin.y = self.headerHeight;
                    self.segmentedView.frame = frame;
                    [self.headerContainerView addSubview:self.segmentedView];
                }
            }
        }
    }else {
        self.hoverType = LBPageSmoothHoverTypeTop;
        if (self.headerContainerView.superview != self) {
            CGRect frame = self.headerContainerView.frame;
            frame.origin.y = - (self.headerHeight - self.ceilPointHeight);
            self.headerContainerView.frame = frame;
            [self addSubview:self.headerContainerView];
        }
        
        if (self.isControlVerticalIndicator) {
            self.currentListScrollView.showsVerticalScrollIndicator = YES;
        }
        
        if (self.syncListContentOffsetEnabled) {
            self.syncListContentOffsetEnabled = NO;
            self.currentHeaderContainerViewY = -(self.headerHeight - self.ceilPointHeight);
            for (id listItem in self.listDict.allValues) {
                if (listItem.listScrollView != scrollView) {
                    [listItem.listScrollView setContentOffset:CGPointMake(0, -(self.segmentedHeight + self.ceilPointHeight)) animated:NO];
                }
            }
        }
    }
    CGPoint contentOffset = CGPointMake(scrollView.contentOffset.x, contentOffsetY);
    if ([self.delegate respondsToSelector:@selector(smoothView:listScrollViewDidScroll:contentOffset:)]) {
        [self.delegate smoothView:self listScrollViewDidScroll:scrollView contentOffset:contentOffset];
    }
  

  }
  }

• (void)loadHeaderAndSegmentedView {
  self.headerView = [self.dataSource headerViewInSmoothView:self];
  self.segmentedView = [self.dataSource segmentedViewInSmoothView:self];
  [self.headerContainerView addSubview:self.headerView];
  [self.headerContainerView addSubview:self.segmentedView];

  self.headerHeight = self.headerView.bounds.size.height;
  self.segmentedHeight = self.segmentedView.bounds.size.height;
  self.headerContainerHeight = self.headerHeight + self.segmentedHeight;
  }

• (void)refreshWidthCompletion:(void(^)(CGSize size))completion {
  if (self.bounds.size.width == 0) {
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  !completion ? : completion(self.bounds.size);
  });
  }else {
  !completion ? : completion(self.bounds.size);
  }
  }

• (void)horizontalScrollDidEndAtIndex:(NSInteger)index {
  self.currentIndex = index;
  UIView *listHeader = self.listHeaderDict[@(index)];
  UIScrollView *listScrollView = self.listDict[@(index)].listScrollView;
  self.currentListScrollView = listScrollView;
  if (self.isOnTop) return;
  if (listHeader != nil && listScrollView.contentOffset.y <= -(self.segmentedHeight + self.ceilPointHeight)) {
  for (id listItem in self.listDict.allValues) {
  listItem.listScrollView.scrollsToTop = (listItem.listScrollView == listScrollView);
  }
  CGRect frame = self.headerContainerView.frame;
  frame.origin.y = 0;
  self.headerContainerView.frame = frame;
  if (self.headerContainerView.superview != listHeader) {
  [listHeader addSubview:self.headerContainerView];
  }
  }
  }

• (UIView *)listHeaderForListScrollView:(UIScrollView *)scrollView {
  for (NSNumber *index in self.listDict) {
  if (self.listDict[index].listScrollView == scrollView) {
  return self.listHeaderDict[index];
  }
  }
  return nil;
  }

• (NSInteger)listIndexForListScrollView:(UIScrollView *)scrollView {
  for (NSNumber *index in self.listDict) {
  if (self.listDict[index].listScrollView == scrollView) {
  return index.integerValue;
  }
  }
  return 0;
  }

• (void)listDidAppear:(NSInteger)index {
  NSUInteger count = [self.dataSource numberOfListsInSmoothView:self];
  if (count <= 0 || index >= count) return;

  id list = self.listDict[@(index)];
  if (list && [list respondsToSelector:@selector(listViewDidAppear)]) {
  [list listViewDidAppear];
  }
  }

• (void)listDidDisappear:(NSInteger)index {
  NSUInteger count = [self.dataSource numberOfListsInSmoothView:self];
  if (count <= 0 || index >= count) return;

  id list = self.listDict[@(index)];
  if (list && [list respondsToSelector:@selector(listViewDidDisappear)]) {
  [list listViewDidDisappear];
  }
  }

• (void)allowScrolling:(UIScrollView *)scrollView {
  scrollView.bounces = self.originBounces;
  scrollView.showsVerticalScrollIndicator = self.originShowsVerticalScrollIndicator;
  }

• (void)forbidScrolling:(UIScrollView *)scrollView {
  scrollView.contentOffset = CGPointZero;
  scrollView.bounces = NO;
  scrollView.showsVerticalScrollIndicator = NO;
  }

• (void)dragBegan {
  self.isOnTop = YES;
  [self setupShowingLayout];
  }

• (void)dragDismiss {
  [UIView animateWithDuration:0.25 animations:^{
  CGRect frame = self.bottomContainerView.frame;
  frame.origin.y = self.frame.size.height - self.segmentedHeight;
  self.bottomContainerView.frame = frame;
  } completion:^(BOOL finished) {
  [self setupDismissLayout];

    self.isOnTop = NO;
    if ([self.delegate respondsToSelector:@selector(smoothViewDragEnded:isOnTop:)]) {
        [self.delegate smoothViewDragEnded:self isOnTop:self.isOnTop];
    }
  

  }];
  }

• (void)dragShowing {
  [UIView animateWithDuration:0.25 animations:^{
  CGRect frame = self.bottomContainerView.frame;
  frame.origin.y = self.ceilPointHeight;
  self.bottomContainerView.frame = frame;
  } completion:^(BOOL finished) {
  if ([self.delegate respondsToSelector:@selector(smoothViewDragEnded:isOnTop:)]) {
  [self.delegate smoothViewDragEnded:self isOnTop:self.isOnTop];
  }
  }];
  }

• (void)setupShowingLayout {
  // 将headerContainerView添加到self
  if (self.headerContainerView.superview != self) {
  CGRect frame = self.headerContainerView.frame;
  frame.origin.y = -(self.currentListScrollView.contentOffset.y + self.headerContainerHeight);
  self.headerContainerView.frame = frame;
  [self insertSubview:self.headerContainerView belowSubview:self.bottomContainerView];
  }

  // 将listCollectionView添加到bottomContainerView
  if (self.listCollectionView.superview != self.bottomContainerView) {
  CGRect frame = self.listCollectionView.frame;
  frame.origin.y = self.segmentedHeight;
  frame.size.height = self.bottomContainerView.frame.size.height - self.segmentedHeight;
  self.listCollectionView.frame = frame;
  [self.bottomContainerView addSubview:self.listCollectionView];
  self->_listCollectionView.headerContainerView = nil;

    // 记录当前列表的滑动位置
    self.currentListPanBeganContentOffsetY = self.currentListScrollView.contentOffset.y;
    
    for (id list in self.listDict.allValues) {
        list.listScrollView.contentInset = UIEdgeInsetsZero;
        list.listScrollView.contentOffset = CGPointZero;
        
        CGRect frame = list.listView.frame;
        frame.size = self.listCollectionView.bounds.size;
        list.listView.frame = frame;
    }
  

  }
  }

• (void)setupDismissLayout {
  UIView *listHeader = [self listHeaderForListScrollView:self.currentListScrollView];
  if (self.headerContainerView.superview != listHeader) {
  CGRect frame = self.headerContainerView.frame;
  frame.origin.y = 0;
  self.headerContainerView.frame = frame;
  [listHeader addSubview:self.headerContainerView];
  }

  if (self.listCollectionView.superview != self) {
  self.listCollectionView.frame = self.bounds;
  [self insertSubview:self.listCollectionView belowSubview:self.bottomContainerView];
  self->_listCollectionView.headerContainerView = self.headerContainerView;

    for (id list in self.listDict.allValues) {
        list.listScrollView.contentInset = UIEdgeInsetsMake(self.headerContainerHeight, 0, 0, 0);
        list.listScrollView.contentOffset = CGPointZero;
        
        CGRect frame = list.listView.frame;
        frame.size = self.listCollectionView.bounds.size;
        list.listView.frame = frame;
    }
    self.currentListScrollView.contentOffset = CGPointMake(0, self.currentListPanBeganContentOffsetY);
  

  }
  }

#pragma mark - Getter

• (UICollectionView *)listCollectionView {
  if (!_listCollectionView) {
  UICollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
  layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
  layout.minimumLineSpacing = 0;
  layout.minimumInteritemSpacing = 0;
  _listCollectionView = [[GKPageSmoothCollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
  _listCollectionView.dataSource = self;
  _listCollectionView.delegate = self;
  _listCollectionView.pagingEnabled = YES;
  _listCollectionView.bounces = NO;
  _listCollectionView.showsHorizontalScrollIndicator = NO;
  _listCollectionView.scrollsToTop = NO;
  [_listCollectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:GKPageSmoothViewCellID];
  if (@available(iOS 11.0, *)) {
  _listCollectionView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
  }
  if (@available(iOS 10.0, *)) {
  _listCollectionView.prefetchingEnabled = NO;
  }
  _listCollectionView.backgroundColor = [UIColor clearColor];
  _listCollectionView.headerContainerView = self.headerContainerView;
  }
  return _listCollectionView;
  }

• (UIView *)headerContainerView {
  if (!_headerContainerView) {
  _headerContainerView = [UIView new];
  }
  return _headerContainerView;
  }

• (UIView *)bottomContainerView {
  if (!_bottomContainerView) {
  _bottomContainerView = [UIView new];
  _bottomContainerView.backgroundColor = UIColor.whiteColor;
  }
  return _bottomContainerView;
  }

• (UIPanGestureRecognizer *)panGesture {
  if (!_panGesture) {
  _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePanGesture:)];
  _panGesture.delegate = self;
  }
  return _panGesture;
  }

@end
``