从用户照片库加载图像并更新UICollectionView

Question

So i have UICollectionView . I need to get all user photos from his photos library and when photo is loaded update my collection view. I tried using NSNotificationCenter . I added observer to UICollectionViewController and when i enumerate photos i post notification so i could update my collection view when photo us loaded. Here is my controller:

  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(phonePhotoLoaded:) name:@"PhonePhotoLoaded" object:nil]; [self.manager getPhonePhotos]; 

Selector method:

 -(void)phonePhotoLoaded:(NSNotification *)userInfo { [self.collectionView performBatchUpdates:^{ NSDictionary *dic = [userInfo valueForKey:@"userInfo"]; [self.photos addObject:[dic valueForKey:@"photo"]]; [self.collectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:self.photos.count inSection:0]]]; } completion:^(BOOL finished){ }]; 

}

And in [self.manager getPhonePhotos]

 ALAssetsLibrary *al = [PhotoManager defaultAssetsLibrary]; [al enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop){ [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop){ if ([[asset valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]) { NSDictionary *userPhotos = [NSDictionary dictionaryWithObjectsAndKeys:asset, @"photo", nil]; [[NSNotificationCenter defaultCenter] postNotificationName:@"PhonePhotoLoaded" object:self userInfo:userPhotos]; } }]; }failureBlock:^(NSError *error) { ;} ]; 

This is what error i get:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'too many update animations on one view - limit is 31 in flight at a time (; }; layer = >)'

So as much as i understand, when i enumerate photos, i post notification, then notification method is executed but UICollectionView is not making animations. He somehow starts them when i finish enumerating. So how could i update my UI when photo is fetched? Any ideas?

Answer 1

Don't post a notification on each iteration of the photo enumeration (each time your block is called). Instead, build up an array of all of the assets and post it on the last call of the block (IIRC, the asset will be nil on the last call, need to check the docs).

Your current problem is that you are starting lots of animations by posting a notification each time and you should really collate all of your changes and then execute a single performBatchUpdates .