UICollectionView在部分之间重新布置项目时崩溃 | UICollectionView在部分之间重新布置项目时崩溃

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问题描述

我无法在 UICollectionView 中的部分之间动画变化，我的程序会不断崩溃，它有什么问题？

我有一个集合视图，其中包含四个部分：

我想将其转换为只有三个具有相同项目的部分：

我想对这个转换进行动画处理：

  //初始状态
 
 NSArray * source = @ [@ [@A]，@ [@B]，@ [@C @ [@D]]; 
 
 
 //一些数据源方法
 
  - （NSInteger）collectionView：（UICollectionView *）collectionView numberOfItemsInSection：（NSInteger）section 
 {
 return [source [section] count]; 
} 
 
  - （NSInteger）numberOfSectionsInCollectionView：（UICollectionView *）collectionView 
 {
 return [source count]; 
} 
 
 
 //转换：工作，但我必须保留一个空段
 
 source = @ [@ [@A] ，@ [@B，C]，@ [@D]，@ []]; 
 
 [collection performBatchUpdates：^ {
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：0] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：0] 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：1] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：1]]; 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：2] 
 toIndexPath：[NSIndexPath indexPathForItem：1 inSection：1]]; 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：3] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：2]]; 
} completion：nil]; 
 
 
 //转换：崩溃！ 
 
 source = @ [@ [@A]，@ [@B，@C]，@ [@D]]; 
 
 [collection performBatchUpdates：^ {
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：0] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：0] 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：1] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：1]]; 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：2] 
 toIndexPath：[NSIndexPath indexPathForItem：1 inSection：1]]; 
 [collection moveItemAtIndexPath：[NSIndexPath indexPathForItem：0 inSection：3] 
 toIndexPath：[NSIndexPath indexPathForItem：0 inSection：2]]; 
 [collection deleteSections：[NSIndexSet indexSetWithIndex：3]]; 
} completion：nil];

我不断得到崩溃，或者内部断言失败： [UICollectionView _endItemAnimations] ... ，有时更奇怪，一个malloc错误：对于释放的对象不正确的校验和... p>

如果我不调用 deleteSections：，它也不工作。如果我放在第一，它不改变任何东西。如果我删除具有相同源和目标的 moveItemAtIndexPath：toIndexPath：，它不会更改任何内容。如果我不在一个批处理块，它显然崩溃在第一个命令。
我忽略了什么？

解决方案

这个非常有趣的一个摘录关于UICollectionView：

知道这一点，我发现这并不奇怪，删除的部分和 moveItemFromIndexPath：toIndexPath 不能一起很好地工作。我想这是同样的错误。

我使用的解决方案：

我把一个假的看不见的细胞放在我应该删除的部分。这允许我保持相同的行为，如果我做了一个 moveItemFromIndexPath：toIndexPath：。当然，我相应地修改了我的数据源！

I have trouble animating changes between sections in a UICollectionView, my program keeps crashing, what is wrong with it?

I have a collection view which has four sections:

I want to transform it to have only three sections with the same items:

And I want to animate this transformation:

// Initial state

NSArray *source = @[ @[@"A"], @[@"B"], @[@"C"], @[@"D"] ];


// Some data source methods

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return [source[section] count];
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return [source count];
}


// Transformation: that works but I have to keep an empty section

source = @[ @[@"A"], @[@"B", @"C"], @[@"D"], @[] ];

[collection performBatchUpdates:^{
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:1]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:1]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:2]
                        toIndexPath:[NSIndexPath indexPathForItem:1 inSection:1]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:3]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:2]];
} completion:nil];


// Transformation: that crashes!

source = @[ @[@"A"], @[@"B", @"C"], @[@"D"] ];

[collection performBatchUpdates:^{
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:1]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:1]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:2]
                        toIndexPath:[NSIndexPath indexPathForItem:1 inSection:1]];
    [collection moveItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:3]
                        toIndexPath:[NSIndexPath indexPathForItem:0 inSection:2]];
    [collection deleteSections:[NSIndexSet indexSetWithIndex:3]];
} completion:nil];

I keep getting crashes, either an internal assertion failure: Assertion failure in -[UICollectionView _endItemAnimations]..., or sometimes, even more weird, a malloc error: incorrect checksum for freed object....

If I don't call deleteSections: it doesn't work either. If I put first, it doesn't change anything. If I remove the moveItemAtIndexPath:toIndexPath: which have the same source and destination, it doesn't change anything. If I don't do it in a batch block, it obviously crashes at the first command.Did I overlook something?

解决方案

An extract from this very interesting article about UICollectionView:

Knowing this, I find it not surprising at all that deleting of section and moveItemFromIndexPath:toIndexPath do not work well together either. I guess it's "kind of the same bug".

The solution I used:

I put a fake invisible cell in the section I should have deleted. That permitted me to keep the same behavior as if I had done a moveItemFromIndexPath:toIndexPath:. Of course, I adapted my datasource accordingly!

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