删除最后一个 UICollectionViewCell 时出现 NSRangeException [英] NSRangeException when deleting last UICollectionViewCell

问题描述

我有一个带有 1 个部分的 UICollectionView.用户可以从集合中删除单元格，我使用此代码进行删除:

[self.collectionView performBatchUpdates:^{[self.collectionView deleteItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:i inSection:0]]];[self.media removeObjectAtIndex:i];} 完成:无];

这对除了集合中的最后一个单元格之外的每个单元格都有效，每次都会使应用程序崩溃并出现错误:由于未捕获的异常'NSRangeException'而终止应用程序，原因:'*** -[__NSArrayMobjectAtIndex:]: index 3 越界[0 .. 2]

NSZombies 没有向我显示堆栈跟踪，因此我在代码中访问数组但没有命中的每一行都放置了一个断点，我发现在 deleteItemsAtIndexPaths 之后引发了此错误，numberOfSectionsInCollectionView 和 sizeForItemAtIndexPath，但在 numberOfItemsInSection 和 cellForItemAtIndexPath

之前

什么可能导致此崩溃?如何调试?

有一些类似的 SO 帖子，但是这个 2 年前的帖子没有答案

I have a UICollectionView with 1 section. The user can delete cells from the collection, and I use this code for removal:

[self.collectionView performBatchUpdates:^{
   [self.collectionView deleteItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:i inSection:0]]];
   [self.media removeObjectAtIndex:i];
} completion:nil];

This works fine for every cell except for the last cell in the collection, which crashes the app every time with the error: Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 3 beyond bounds [0 .. 2]

NSZombies aren't showing me a stack trace so I put a breakpoint on every line in my code that accesses an array but none were hit, and I found that this error is thrown after deleteItemsAtIndexPaths, numberOfSectionsInCollectionView and sizeForItemAtIndexPath, but before numberOfItemsInSection and cellForItemAtIndexPath

What could be causing this crash? How can I debug it?

There are some similar SO posts, but this one from 2 years ago has no answer UICollectionView crash when deleting last item, and this one only solves the problem if you want to delete the whole section: Removing the last Cell in UICollectionView makes a Crash

UPDATE, here are the data source delegate methods that run before the crash:

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}
-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return CGSizeMake(floorf(screenWidth/3), 200);
}

解决方案

Just put the Exceptions Breakpoint and you'll find where exactly it is crashing.

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