ios - UICollectionView 无效索引路径崩溃

Question

我在 UICollectionView 尝试滚动到无效索引路径 {length = 2, path = 0 - 0} 时发生崩溃。

这是否意味着我的 Collection View 大小为 2，但我试图滚动到第 0 节索引 0？在这种情况下，这不是一个有效的卷轴吗？

从那以后，我们已经消除了使用 NSFetchedResultsController 的不必要的复杂性，这可能导致崩溃，但我仍然对错误消息的读取方式及其含义感到好奇？

这是代码

void fetch() {

   // get data from core data using a FetchRequest
   do a perform fetch to get my item

   // loop through to see which index the item I want is at
   loop through result {
      if (my id matches core data id) {
          self.selectedIndex = x;
       }
    }

    // get more from core data using a Fetch Request
    create another FetchedResultsController
    do another fetch to get all other items

    [self.myCV reloadData];

    // find the index path for the item I want to scroll to
    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:self.selectedIndex inSection:0];

    [self.myCV scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally | UICollectionViewScrollPositionCenteredVertically animated:NO];
}

// UICollectionView delegate methods
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return [[self.fetchedResultsController sections] count];
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    id<NSFetchedResultsSectionInfo> secInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    return [secInfo numberOfObjects];
}

Answer 1

我们也收到了很多相同的崩溃反馈，
原因是reloadData后立即使用scrollToItemAtIndexPath方法，我们使用这段代码成功修复。

[self.myCV reloadData];
[self.myCV.collectionViewLayout invalidateLayout];
if (self.myCV.numberOfSections != 0) {
     NSIndexPath *indexPath = [NSIndexPath indexPathForItem:self.selectedIndex inSection:0];
    [self.myCV scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally | UICollectionViewScrollPositionCenteredVertically animated:NO];
}