iOS - 实现scrollView和collectionView自定义分页

//主要代码

• (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
  CGFloat x = targetContentOffset->x;
  CGFloat pageWidth = itemWidth + 20;
  CGFloat movedX = x - pageWidth * selectedIndex;
  if (movedX < -pageWidth * 0.5) {
  // Move left
  selectedIndex--;
  } else if (movedX > pageWidth * 0.5) {
  // Move right
  selectedIndex++;
  }

  if (ABS(velocity.x) >= 2){
  targetContentOffset->x = pageWidth * selectedIndex;
  } else {
  targetContentOffset->x = scrollView.contentOffset.x;
  [scrollView setContentOffset:CGPointMake(pageWidth * selectedIndex, scrollView.contentOffset.y) animated:YES];
  }
  NSLog(@"%ld",selectedIndex);
  }