CollectionView的NSFetchedResultsContollerDelegate [英] NSFetchedResultsContollerDelegate for CollectionView

问题描述

我想在CollectionViewController中使用NSFetchedResultsControllerRelegate。
因此，我只是改变了TableViewController的CollectionView的方法。

I'd like to use the NSFetchedResultsControllerRelegate in a CollectionViewController. Therefore I just changed the method for the TableViewController for the CollectionView.

(void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
       atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.collectionView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]];
            break;

        case NSFetchedResultsChangeDelete:
            [self.collectionView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] ];

       break;
    }
}


(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
   atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
  newIndexPath:(NSIndexPath *)newIndexPath {

  UICollectionView *collectionView = self.collectionView;

  switch(type) {

    case NSFetchedResultsChangeInsert:
        [collectionView insertItemsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]];
        break;

    case NSFetchedResultsChangeDelete:
        [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];
        break;

    case NSFetchedResultsChangeUpdate:
        [collectionView reloadItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];
        break;

    case NSFetchedResultsChangeMove:
        [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];
        [collectionView insertItemsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]];
        break;
  }
}

(void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
   [self.collectionView reloadData];
}

但我不知道如何处理 WillChangeContent （ beginUpdates for TableView ）和 DidChangeContent （ endUpdates >。

But I do not know how to handle the WillChangeContent (beginUpdates for TableView) and DidChangeContent (endUpdates for TableView) for a CollectionView.

一切正常，除非我将一个项目从一个部分移动到另一个部分。然后我得到以下错误。

Everything works fine except when I move one item from one section to another section. Then I get the following error.

这通常是NSManagedObjectContextObjectsDidChangeNotification的观察者中的错误。无效的更新：第0部分中的项目数目无效....

This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification. Invalid update: invalid number of items in section 0....

任何想法如何解决这个问题？

Any idea how can I solve this issue?

推荐答案

将获取的结果控制器与集合视图组合有点棘手。

Combining a fetched results controller with a collection view is a bit tricky. The problem is explained in

• http://ashfurrow.com/blog/how-to-use-nsfetchedresultscontroller-with-uicollectionview

• http://ashfurrow.com/blog/how-to-use-nsfetchedresultscontroller-with-uicollectionview

如果你正在寻找如何使用
来解决
NSInternalInconsistencyException 运行时异常 UICollectionView ，我有一个关于GitHub的例子，详细说明如何对NSFetchedResultsControllerDelegate中的
更新进行排队。

If you're looking for how to get around the NSInternalInconsistencyException runtime exception with UICollectionView, I have an example on GitHub detailing how to queue updates from the NSFetchedResultsControllerDelegate.

问题是现有的 UITableView 类使用 beginUpdates
和 endUpdates 将批次提交到表视图。 UICollectionView
有一个新的 performBatchUpdates：方法，它使用块参数
更新集合视图。这是性感的，但它不工作良好
与现有的范例NSFetchedResultsController。

The problem is that the existing UITableView class uses beginUpdates and endUpdates to submit batches to the table view. UICollectionView has a new performBatchUpdates: method, which takes a block parameter to update the collection view. That's sexy, but it doesn't work well with the existing paradigm for NSFetchedResultsController.

幸运的是，该文章还提供示例实现：

Fortunately, that article also provides a sample implementation:

• https：// github.com/AshFurrow/UICollectionView-NSFetchedResultsController

• https://github.com/AshFurrow/UICollectionView-NSFetchedResultsController

从README：

这是一个如何使用新的 UICollectionView 和
NSFetchedResultsController 。诀窍是通过 NSFetchedResultsControllerDelegate 将
的更新排队，直到控制器
完成它的更新。 UICollectionView 没有相同的
beginUpdates 和 endUpdates UITableView 必须让它工作轻松
与 NSFetchedResultsController ，所以你必须排队他们或者你得到
内部一致性运行时异常。

This is an example of how to use the new UICollectionView with NSFetchedResultsController. The trick is to queue the updates made through the NSFetchedResultsControllerDelegate until the controller finishes its updates. UICollectionView doesn't have the same beginUpdates and endUpdates that UITableView has to let it work easily with NSFetchedResultsController, so you have to queue them or you get internal consistency runtime exceptions.

这篇关于CollectionView的NSFetchedResultsContollerDelegate的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！