uitableview sectionTextTitle 滾動顯示時可以做點什么。可以參考這個方法

代碼來自：CityPickerViewController
https://github.com/guoshimeihua/CityPickerViewController

• (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index {
  [self showIndexTitle:title];

  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  [self dissmissIndexTitle];
  });

  return [_indexArray[index] integerValue];
  }

• (void)showIndexTitle:(NSString *)indexTitle {
  self.view.userInteractionEnabled = NO;
  self.indexTitleLabel.text = indexTitle;
  [self.view addSubview:self.indexTitleLabel];
  }

• (void)dissmissIndexTitle {
  self.view.userInteractionEnabled = YES;
  [self.indexTitleLabel removeFromSuperview];
  }

• (void)labelPrepare {
  self.indexTitleLabel.backgroundColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:0.4];
  self.indexTitleLabel.center = self.view.center;
  self.indexTitleLabel.bounds = CGRectMake(0, 0, 120, 120);
  self.indexTitleLabel.font = [UIFont boldSystemFontOfSize:80];
  self.indexTitleLabel.textAlignment = NSTextAlignmentCenter;
  self.indexTitleLabel.textColor = [UIColor whiteColor];
  }