- (void)layoutSubviews {
 [self resetContentOffsetIfNeeded];
 [super layoutSubviews];
}

- (void)resetContentOffsetIfNeeded {
 CGPoint contentOffset = self.contentOffset;
 //头部
 if (contentOffset.y < 0.0) {
  contentOffset.y = self.contentSize.height / 3.0;
 }
 //尾部
 else if (contentOffset.y >= (self.contentSize.height - self.bounds.size.height)) {
  contentOffset.y = self.contentSize.height / 3.0 - self.bounds.size.height;
 }
 [self setContentOffset: contentOffset];
}

@interface SUTableViewInterceptor : NSObject

@property (nonatomic, weak) id receiver;
@property (nonatomic, weak) id middleMan;

@end

- (void)setDataSource:(id<UITableViewDataSource>)dataSource {
 self.dataSourceInterceptor.receiver = dataSource;
 [super setDataSource:(id<UITableViewDataSource>)self.dataSourceInterceptor];
}

- (SUTableViewInterceptor *)dataSourceInterceptor {
 if (!_dataSourceInterceptor) {
  _dataSourceInterceptor = [[SUTableViewInterceptor alloc]init];
  _dataSourceInterceptor.middleMan = self;
 }
 return _dataSourceInterceptor;
}

- (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section {
 self.actualRows = [self.dataSourceInterceptor.receiver tableView:tableView numberOfRowsInSection:section];
 return self.actualRows * 3;
}

- (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
 NSIndexPath * actualIndexPath = [NSIndexPath indexPathForRow:indexPath.row % self.actualRows inSection:indexPath.section];
 return [self.dataSourceInterceptor.receiver tableView:tableView cellForRowAtIndexPath:actualIndexPath];
}

@implementation SUTableViewInterceptor

#pragma mark - forward & response override
- (id)forwardingTargetForSelector:(SEL)aSelector {
 if ([self.middleMan respondsToSelector:aSelector]) return self.middleMan;
 if ([self.receiver respondsToSelector:aSelector]) return self.receiver;
 return [super forwardingTargetForSelector:aSelector];
}

- (BOOL)respondsToSelector:(SEL)aSelector {
 if ([self.middleMan respondsToSelector:aSelector]) return YES;
 if ([self.receiver respondsToSelector:aSelector]) return YES;
 return [super respondsToSelector:aSelector];
}

@end

- (void)viewDidLoad {
 [super viewDidLoad];
 [self.view addSubview:self.tableView];
}

- (UITableView *)tableView {
 if(!_tableView) {
  _tableView = [[SUTableView alloc] initWithFrame:self.view.bounds style:UITableViewStylePlain];
  _tableView.delegate = self;
  _tableView.dataSource = self;
  _tableView.showsVerticalScrollIndicator = NO;
  _tableView.rowHeight = 150.0;
  [_tableView registerNib:[UINib nibWithNibName:@"LiveCell" bundle:nil] forCellReuseIdentifier:liveCellID];
 }
 return _tableView;
}

#pragma mark - UITableViewDataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
 return 5;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
 LiveCell * cell = [self.tableView dequeueReusableCellWithIdentifier:liveCellID];
 cell.selectionStyle = UITableViewCellSelectionStyleNone;
 cell.descLabel.text = [NSString stringWithFormat:@"第 %ld 个主播频道", indexPath.row + 1];
 return cell;
}