UIScrollViewDelegate

// 触摸屏幕来滚动画面还是其他的方法使得画面滚动，皆触发该函数

• (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  NSLog(@"Scrolling...");
  }

// 触摸屏幕并拖拽画面，再松开，最后停止时，触发该函数

• (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
  NSLog(@"scrollViewDidEndDragging - End of Scrolling.");
  }

// 滚动停止时，触发该函数

• (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  NSLog(@"scrollViewDidEndDecelerating - End of Scrolling.");
  }

// 调用以下函数，来自动滚动到想要的位置，此过程中设置有动画效果，停止时，触发该函数
// UIScrollView的setContentOffset:animated:
// UIScrollView的scrollRectToVisible:animated:
// UITableView的scrollToRowAtIndexPath:atScrollPosition:animated:
// UITableView的selectRowAtIndexPath:animated:scrollPosition:

• (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
  NSLog(@"scrollViewDidEndScrollingAnimation - End of Scrolling.");
  }