UICollectionView＆amp; performBatchUpdates

Question

我试图建立一个应用程序，我可以使用UICollectionviewcontroller＆amp; NSFetchresultcontroller，我找到了以下链接"https://github.com/AshFurrow/UICollectionView-NSFetchedResultsController/blob/master/AFMasterViewController.m

您可以在这里找到代码

#pragma mark - UICollectionVIew

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

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{

    id <NSFetchedResultsSectionInfo> sectionInfo = [self.fetchedResultsController sections][section];
    return [sectionInfo numberOfObjects];
}

// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    AFCollectionViewCell *cell = (AFCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];

    NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath];

#warning Unimplement Cell Configuration

    return cell;
}

#pragma mark - Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController
{
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

#warning Unimplemented fetched results controller

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:<#entity#>inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:<#batch size#>];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:<#descriptor#> ascending:NO];
    NSArray *sortDescriptors = @[sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Master"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
         // Replace this implementation with code to handle the error appropriately.
         // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _fetchedResultsController;
}    

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

    NSMutableDictionary *change = [NSMutableDictionary new];

    switch(type) {
        case NSFetchedResultsChangeInsert:
            change[@(type)] = @[@(sectionIndex)];
            break;
        case NSFetchedResultsChangeDelete:
            change[@(type)] = @[@(sectionIndex)];
            break;
    }

    [_sectionChanges addObject:change];
}

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

    NSMutableDictionary *change = [NSMutableDictionary new];
    switch(type)
    {
        case NSFetchedResultsChangeInsert:
            change[@(type)] = newIndexPath;
            break;
        case NSFetchedResultsChangeDelete:
            change[@(type)] = indexPath;
            break;
        case NSFetchedResultsChangeUpdate:
            change[@(type)] = indexPath;
            break;
        case NSFetchedResultsChangeMove:
            change[@(type)] = @[indexPath, newIndexPath];
            break;
    }
    [_objectChanges addObject:change];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    if ([_sectionChanges count] > 0)
    {
        [self.collectionView performBatchUpdates:^{

            for (NSDictionary *change in _sectionChanges)
            {
                [change enumerateKeysAndObjectsUsingBlock:^(NSNumber *key, id obj, BOOL *stop) {

                    NSFetchedResultsChangeType type = [key unsignedIntegerValue];
                    switch (type)
                    {
                        case NSFetchedResultsChangeInsert:
                            [self.collectionView insertSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
                            break;
                        case NSFetchedResultsChangeDelete:
                            [self.collectionView deleteSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
                            break;
                        case NSFetchedResultsChangeUpdate:
                            [self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:[obj unsignedIntegerValue]]];
                            break;
                    }
                }];
            }
        } completion:nil];
    }

    if ([_objectChanges count] > 0 && [_sectionChanges count] == 0)
    {
        [self.collectionView performBatchUpdates:^{

            for (NSDictionary *change in _objectChanges)
            {
                [change enumerateKeysAndObjectsUsingBlock:^(NSNumber *key, id obj, BOOL *stop) {

                    NSFetchedResultsChangeType type = [key unsignedIntegerValue];
                    switch (type)
                    {
                        case NSFetchedResultsChangeInsert:
                            [self.collectionView insertItemsAtIndexPaths:@[obj]];
                            break;
                        case NSFetchedResultsChangeDelete:
                            [self.collectionView deleteItemsAtIndexPaths:@[obj]];
                            break;
                        case NSFetchedResultsChangeUpdate:
                            [self.collectionView reloadItemsAtIndexPaths:@[obj]];
                            break;
                        case NSFetchedResultsChangeMove:
                            [self.collectionView moveItemAtIndexPath:obj[0] toIndexPath:obj[1]];
                            break;
                    }
                }];
            }
        } completion:nil];
    }

    [_sectionChanges removeAllObjects];
    [_objectChanges removeAllObjects];
}

@end

我有以下错误

NSFetchedResultsController during a call to -controllerDidChangeContent:.  -[__NSArrayI unsignedIntegerValue]

_sectionsChange的NS日志给我以下输出

1 =         (
        6
    );

我想知道如何解决这个问题，所以任何帮助都会受到赞赏

谢谢

Answer 1

不，我在更新以下代码后修复了错误：

{
case NSFetchedResultsChangeInsert:
                            [self.collectionView insertItemsAtIndexPaths:@[obj]];
                            [self.collectionView.window endEditing:YES];
                            break;
}

而非案例NSFetchedResultsChangeInsert：

[self.collectionView insertItemsAtIndexPaths:@[obj]];
break;

然后删除所有对象，从头开始创建所有内容，解决问题！