如果实现了代理方法返回头部脚部视图，如果我只返回头部 脚部返回nil会直接崩溃

[zhangxiongwen]

//返回头脚视图

• (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
  // CollectionHeaderAndFooterView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"sectionHeader" forIndexPath:indexPath];
  // headerView.titleLabel.text = @"头视图";
  // headerView.titleLabel.backgroundColor = [UIColor orangeColor];
  // return headerView;
  return nil;

  }else{
  CollectionHeaderAndFooterView *footerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"sectionFooter" forIndexPath:indexPath];
  footerView.titleLabel.text = @"脚视图";
  footerView.titleLabel.backgroundColor = [UIColor cyanColor];
  return footerView;

  }
  }