2020-09-02

Thread 1: Exception: "the view returned from -collectionView:viewForSupplementaryElementOfKind:atIndexPath (UICollectionElementKindSectionFooter, {length = 2, path = 1 - 0}) was not retrieved by calling -dequeueReusableSupplementaryViewOfKind:withReuseIdentifier:forIndexPath: or is nil (>)"

collectionView UICollectionReusableView 没有找到对对应注册的view 需要 viewForSupplementaryElementOfKind代理方法中添加
UICollectionElementKindSectionHeader
UICollectionElementKindSectionFooter
的对应的方法。可以复用的。