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节的UICollectionView。用户可以从集合中删除单元格，并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：nil]; 
  

除了集合中的最后一个单元格之外，每个单元格都可以正常工作，每次都会崩溃应用程序错误：由于未捕获的异常'NSRangeException'终止应用程序，原因：'*** - [__ NSArrayM objectAtIndex：]：索引3超出边界[0 .. 2]

NSZombies没有向我显示堆栈跟踪，所以我在我的代码中的每一行都放了一个断点来访问一个数组，但没有一个被命中，我发现这个错误在 deleteItemsAtIndexPaths ， numberOfSectionsInCollectionView 和 sizeForItemAtIndexPath 之后抛出 numberOfItemsInSection 和 cellForItemAtIndexPath

可能导致此次崩溃的原因？我该怎么调试呢？

有一些类似的SO帖子，但这个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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