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我使用Photos.Framework将从相机拍摄的照片保存到我的画廊并检索它们。FetchAssetsWithLocalIdentifiers返回空数组
这是我用来存储照片的代码：
__block PHAssetCollection *album = [self getMyAlbumWithName:@"MyAlbumName"];
if(album == nil)
{
[self makeAlbumWithTitle:@"MyAlbumName" onSuccess:^(NSString *AlbumId) {
album = [self getMyAlbumWithName:@"MyAlbumName"];
[self addNewAssetWithImage:_imageToStore toAlbum:album onSuccess:^(NSString *ImageId)
{
_imageLocalIdentifier = imageId;
} onError:^(NSError *error) {
// No need to do anything
}];
} onError:^(NSError *error) {
// No need to do anything
}];
}
else
{
[self addNewAssetWithImage:_imageToStore toAlbum:album onSuccess:^(NSString *ImageId)
{
_imageLocalIdentifier = imageId;
} onError:^(NSError *error) {
// No need to do anything
}];
}
-(PHAssetCollection *)getMyAlbumWithName:(NSString*)AlbumName
{
PHFetchResult *assetCollections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum
subtype:PHAssetCollectionSubtypeAlbumRegular
options:nil];
NSLog(@"assetCollections.count = %lu", assetCollections.count);
if (assetCollections.count == 0) return nil;
__block PHAssetCollection * myAlbum;
[assetCollections enumerateObjectsUsingBlock:^(PHAssetCollection *album, NSUInteger idx, BOOL *stop) {
NSLog(@"album:%@", album);
NSLog(@"album.localizedTitle:%@", album.localizedTitle);
if ([album.localizedTitle isEqualToString:AlbumName]) {
myAlbum = album;
*stop = YES;
}
}];
if (!myAlbum) return nil;
return myAlbum;
}
-(void)makeAlbumWithTitle:(NSString *)title onSuccess:(void(^)(NSString *AlbumId))onSuccess onError: (void(^)(NSError * error)) onError
{
//Check weather the album already exist or not
if (![self getMyAlbumWithName:title])
{
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
// Request editing the album.
PHAssetCollectionChangeRequest *createAlbumRequest = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title];
// Get a placeholder for the new asset and add it to the album editing request.
PHObjectPlaceholder * placeHolder = [createAlbumRequest placeholderForCreatedAssetCollection];
if (placeHolder)
{
onSuccess(placeHolder.localIdentifier);
}
} completionHandler:^(BOOL success, NSError *error) {
NSLog(@"Finished adding asset. %@", (success ? @"Success" : error));
if (error)
{
onError(error);
}
}];
}
}
-(void)addNewAssetWithImage:(UIImage *)image
toAlbum:(PHAssetCollection *)album
onSuccess:(void(^)(NSString *ImageId))onSuccess
onError: (void(^)(NSError * error)) onError
{
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
// Request creating an asset from the image.
PHAssetChangeRequest *createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
// Request editing the album.
PHAssetCollectionChangeRequest *albumChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:album];
// Get a placeholder for the new asset and add it to the album editing request.
PHObjectPlaceholder * placeHolder = [createAssetRequest placeholderForCreatedAsset];
[albumChangeRequest addAssets:@[ placeHolder ]];
NSLog(@"%@",placeHolder.localIdentifier);
if (placeHolder) {
onSuccess(placeHolder.localIdentifier);
}
} completionHandler:^(BOOL success, NSError *error) {
NSLog(@"Finished adding asset. %@", (success ? @"Success" : error));
if (error) {
onError(error);
}
}];
}
这是我使用来获取这张照片的代码：
PHImageManager *imgManager = [[PHImageManager alloc] init];
PHFetchResult* fetchResult = [PHAsset fetchAssetsWithLocalIdentifiers:@[_imageLocalIdentifier] options:nil];
if([fetchResult count] > 0)
{
PHAsset *asset = [fetchResult objectAtIndex:0];
PHImageRequestOptions *option = [PHImageRequestOptions new];
option.synchronous = NO;
option.version = PHImageRequestOptionsVersionCurrent;
option.networkAccessAllowed = YES;
option.deliveryMode = PHImageRequestOptionsDeliveryModeOpportunistic;
option.resizeMode = PHImageRequestOptionsResizeModeFast;
[imgManager requestImageForAsset:asset
targetSize:CGSizeMake(CAMERA_GALLERY_SIZE, CAMERA_GALLERY_SIZE)
contentMode:PHImageContentModeDefault
options:option
resultHandler:^(UIImage *result, NSDictionary *info) {
[cell.photoIV setImage:result];
}];
}
有了这一段代码，存储12张照片的样本（它们在我的相册中都可以）4或5个本地标识符返回一个空的提取结果。 这是在iOS 8，iOS 9和iOS 10中测试的（对于iOS 10，情况确实更糟，因为几乎所有的提取结果都是空的）。
我读过类似的东西是以前版本的iOS中的错误，但我想现在不是这个原因。
我已经用这种方法尝试取回照片：
- (PHAsset *)getAssetFromGallery:(NSString *)identifier
{
PHAsset *asset = [PHAsset fetchAssetsWithLocalIdentifiers:@[identifier] options:nil].lastObject;
if(asset != nil)
return asset;
__block PHAsset *result;
PHFetchResult *userAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAny options:nil];
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
[fetchOptions setPredicate:[NSPredicate predicateWithFormat:@"localIdentifier == %@", identifier]];
[userAlbums enumerateObjectsUsingBlock:^(id _Nonnull objectCollection, NSUInteger idx, BOOL * _Nonnull stopCollectionEnumeration) {
PHAssetCollection *collection = nil;
if(![objectCollection isKindOfClass:[PHAssetCollection class]])
return;
collection = (PHAssetCollection *)objectCollection;
PHFetchResult *assetsFetchResult = [PHAsset fetchAssetsInAssetCollection:collection options:fetchOptions];
[assetsFetchResult enumerateObjectsUsingBlock:^(id _Nonnull objectAsset, NSUInteger idx, BOOL * _Nonnull stopAssetEnumeration) {
PHAsset *asset = nil;
if(![objectAsset isKindOfClass:[PHAsset class]])
return;
result = asset;
*stopAssetEnumeration = YES;
*stopCollectionEnumeration = YES;
}];
}];
return asset;
}
我试着PHAssetCollectionSubtypeAlbumMyPhotoStream而不是PHAssetCollectionSubtypeAny。 我试过用@"localIdentifier ==[cd] %@"而不是@"localIdentifier == %@". 而且总是得到相同的结果，很多次提取结果都是空的。 有什么想法发生了什么？
你有没有发现前夜的原因呢？同样发生在我身上 – StackOverflower
是的，原因是我打电话给成功（placeHolder.localIdentifier）;在performChanges块内而不是在completionHandler块内。我将用我的代码更新回答我自己的问题，以便您可以检查它。 – Wonton
感谢您的回答，我将检查您的答案:) – StackOverflower