tableview視圖可見范圍內(nèi)cell
NSArray *visiblePaths = [self.tableView indexPathsForVisibleRows];
UICollectionView視圖可見范圍內(nèi)cell
NSArray *visiblePaths = [_collectionView indexPathsForVisibleItems];
刷新某個cell
[self.collectionView reloadItemsAtIndexPaths:@[indexPath]];