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我是objective-c编程的新手。我正在尝试制作我的第一个应用程序，但我无法解决一个问题。

我在我的应用程序中使用 UICollectionView 和 NSFetchedResultController。该应用程序从 Web 下载数据并使用 NSOperationQueue 异步执行此操作。当我在模拟器中测试我的应用程序时一切正常，但是当我在 iPad 3 上测试它时，我经常遇到这个错误。

* -[UICollectionView _endItemAnimations] 中的断言失败，/SourceCache/UIKit/UIKit-2380.17/UICollectionView.m:2801

*由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因：“无效更新：第 0 节中的项目数无效。更新后现有节中包含的项目数 (28) 必须等于其中包含的项目数更新前的那个部分 (26)，加上或减去从该部分插入或删除的项目数（1 插入，0 删除），加上或减去移入或移出该部分的项目数（0 移入，0搬出）。'

我不知道为什么，因为我将 maxConcurrentOperationCount 设置为 1，并且我认为在这种情况下，所有操作都会导致按顺序将项目插入 UICollectionView……可能有什么问题，我应该改变什么？

马图斯

如果有人仍然感兴趣，那是我的代码：

当我的 NSOperation 完成时，我正在调用此方法：

- (void)collectionViewUpdaterDidFinish:(CollectionViewUpdater *)updater {
    [Artwork  artworkWithBehanceInfo:self.projectsData
                        andImageData:updater.imageData
                             atIndex:updater.projectIndex
                  forIndexInDataBase:updater.indexPathInCollectionView.item withDataHelper:self.dataHelper];


    NSIndexPath *indexPath = updater.indexPathInCollectionView;
    [self.dataHelper fetchData];
    [self.myCollectionView insertItemsAtIndexPaths:@[indexPath]];
    [self.pendingOperations.downloadsInProgress removeObjectForKey:indexPath];
    if ([self.dataHelper.fetchedResultsController.fetchedObjects count]==self.numberOfLastItemOnPage){
        [self.refresh endRefreshing];
        [self stopAnimation];
        self.progressView.hidden = YES;
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];

    }
}


- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{

    static NSString *CellIdentifier = @"ResultCell";
    ResultCellView *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];

    Artwork *artwork = [self.dataHelper.fetchedResultsController objectAtIndexPath:indexPath];
    cell.title.text = [artwork.title stringByAppendingString:@"\n "];
    cell.owner.text = [NSString stringWithFormat:@"%@",artwork.owner];
    cell.fields.text = artwork.fields;
    cell.numberOfViews.text = [NSString stringWithFormat:@"%@",artwork.views];
    cell.numberOfLikes.text = [NSString stringWithFormat:@"%@",artwork.likes];
    cell.numberOfComments.text = [NSString stringWithFormat:@"%@",artwork.comments];
    cell.publishedDate.text = artwork.publishedDate;
    if ([artwork.hasThumbnail boolValue]) {
        dispatch_queue_t downloadQueue = dispatch_queue_create("imagecache", NULL);
        dispatch_async(downloadQueue, ^{
            UIImage *productImage = [UIImage imageWithData:artwork.thumbnail];
            CGSize imageSize = productImage.size;
            UIGraphicsBeginImageContext(imageSize);
            [productImage drawInRect:CGRectMake(0, 0, imageSize.width, imageSize.height)];
            productImage = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            dispatch_async(dispatch_get_main_queue(), ^ {
                cell.thumbnailImage.image = productImage;
                cell.thumbnailImage.hidden = NO;
            });
        });


    }
    else {
        NSLog(@"Has to download thumbnail");
        cell.thumbnailImage.hidden = YES;
        [self startOperationsForPhotoRecord:artwork atIndexPath:indexPath];

    }

    if ([self.dataHelper.fetchedResultsController.fetchedObjects count]==self.numberOfLastItemOnPage) {
        self.cellRefreshed = YES;
    }

   // it must be redifined for collections in behance!


    if (indexPath.item >=(self.numberOfLastItemOnPage-10) &&self.cellRefreshed &&([self.projectsData count]%12==0)) {

        self.numberOfFirstItemOnPage = self.numberOfLastItemOnPage+1;
        self.numberOfLastItemOnPage +=12;
        [self downloadMoreProjects];
        self.cellRefreshed = NO;
    }

    cell.selectedBackgroundView = [[UIView alloc] initWithFrame:CGRectZero];
    cell.selectedBackgroundView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5f];



    return cell;
}
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