问题
I'm creating an iOS 5 app. I want to save a photo to the device.
I want to save the photo to an album specific to my app, so I need to create the album, and then save photos to the album.
I know how to create the album:
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library addAssetsGroupAlbumWithName:@"MY APP NAME" resultBlock:^(ALAssetsGroup *group) {
//How to get the album URL?
} failureBlock:^(NSError *error) {
//Handle the error
}];
I want add photos to the new album now, how do I do so? Sample code is greatly appreciated!
回答1:
You may use the following code just change the name of album :
__weak ALAssetsLibrary *lib = self.library;
[self.library addAssetsGroupAlbumWithName:@"My Photo Album" resultBlock:^(ALAssetsGroup *group) {
///checks if group previously created
if(group == nil){
//enumerate albums
[lib enumerateGroupsWithTypes:ALAssetsGroupAlbum
usingBlock:^(ALAssetsGroup *g, BOOL *stop)
{
//if the album is equal to our album
if ([[g valueForProperty:ALAssetsGroupPropertyName] isEqualToString:@"My Photo Album"]) {
//save image
[lib writeImageDataToSavedPhotosAlbum:UIImagePNGRepresentation(image) metadata:nil
completionBlock:^(NSURL *assetURL, NSError *error) {
//then get the image asseturl
[lib assetForURL:assetURL
resultBlock:^(ALAsset *asset) {
//put it into our album
[g addAsset:asset];
} failureBlock:^(NSError *error) {
}];
}];
}
}failureBlock:^(NSError *error){
}];
}else{
// save image directly to library
[lib writeImageDataToSavedPhotosAlbum:UIImagePNGRepresentation(image) metadata:nil
completionBlock:^(NSURL *assetURL, NSError *error) {
[lib assetForURL:assetURL
resultBlock:^(ALAsset *asset) {
[group addAsset:asset];
} failureBlock:^(NSError *error) {
}];
}];
}
} failureBlock:^(NSError *error) {
}];
回答2:
For anyone looking to do this as of iOS 9, things have gotten a bit more complicated since the ALAssetsLibrary is deprecated in favor of the new Photos library.
Here's some Swift code for adding UIImages to a specific album name (creating the album if it doesn't exist), you may need to do some refactoring/optimization for your needs:
func insertImage(image : UIImage, intoAlbumNamed albumName : String) {
//Fetch a collection in the photos library that has the title "albumNmame"
let collection = fetchAssetCollectionWithAlbumName(albumName)
if collection == nil {
//If we were unable to find a collection named "albumName" we'll create it before inserting the image
PHPhotoLibrary.sharedPhotoLibrary().performChanges({
PHAssetCollectionChangeRequest.creationRequestForAssetCollectionWithTitle(albumName)
}, completionHandler: {(success : Bool, error : NSError?) in
if error != nil {
print("Error: " + error!.description)
}
if success {
//Fetch the newly created collection (which we *assume* exists here)
let newCollection = self.fetchAssetCollectionWithAlbumName(albumName)
self.insertImage(image, intoAssetCollection: newCollection!)
}
}
)
} else {
//If we found the existing AssetCollection with the title "albumName", insert into it
self.insertImage(image, intoAssetCollection: collection!)
}
}
func fetchAssetCollectionWithAlbumName(albumName : String) -> PHAssetCollection? {
//Provide the predicate to match the title of the album.
let fetchOption = PHFetchOptions()
fetchOption.predicate = NSPredicate(format: "title == '" + albumName + "'")
//Fetch the album using the fetch option
let fetchResult = PHAssetCollection.fetchAssetCollectionsWithType(
PHAssetCollectionType.Album,
subtype: PHAssetCollectionSubtype.AlbumRegular,
options: fetchOption)
//Assuming the album exists and no album shares it's name, it should be the only result fetched
let collection = fetchResult.firstObject as? PHAssetCollection
return collection
}
func insertImage(image : UIImage, intoAssetCollection collection : PHAssetCollection) {
//Changes for the Photos Library must be maded within the performChanges block
PHPhotoLibrary.sharedPhotoLibrary().performChanges({
//This will request a PHAsset be created for the UIImage
let creationRequest = PHAssetCreationRequest.creationRequestForAssetFromImage(image)
//Create a change request to insert the new PHAsset in the collection
let request = PHAssetCollectionChangeRequest(forAssetCollection: collection)
//Add the PHAsset placeholder into the creation request.
//The placeholder is used because the actual PHAsset hasn't been created yet
if request != nil && creationRequest.placeholderForCreatedAsset != nil {
request!.addAssets([creationRequest.placeholderForCreatedAsset!])
}
},
completionHandler: { (success : Bool, error : NSError?) in
if error != nil {
print("Error: " + error!.description)
}
}
)
}
回答3:
For those looking for Eddy's answer in Objective-C.
#import <Photos/Photos.h>
- (void)insertImage:(UIImage *)image intoAlbumNamed:(NSString *)albumName {
//Fetch a collection in the photos library that has the title "albumNmame"
PHAssetCollection *collection = [self fetchAssetCollectionWithAlbumName: albumName];
if (collection == nil) {
//If we were unable to find a collection named "albumName" we'll create it before inserting the image
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
[PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle: albumName];
} completionHandler:^(BOOL success, NSError * _Nullable error) {
if (error != nil) {
NSLog(@"Error inserting image into album: %@", error.localizedDescription);
}
if (success) {
//Fetch the newly created collection (which we *assume* exists here)
PHAssetCollection *newCollection = [self fetchAssetCollectionWithAlbumName:albumName];
[self insertImage:image intoAssetCollection: newCollection];
}
}];
} else {
//If we found the existing AssetCollection with the title "albumName", insert into it
[self insertImage:image intoAssetCollection: collection];
}
}
- (PHAssetCollection *)fetchAssetCollectionWithAlbumName:(NSString *)albumName {
PHFetchOptions *fetchOptions = [PHFetchOptions new];
//Provide the predicate to match the title of the album.
fetchOptions.predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"title == '%@'", albumName]];
//Fetch the album using the fetch option
PHFetchResult *fetchResult = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:fetchOptions];
//Assuming the album exists and no album shares it's name, it should be the only result fetched
return fetchResult.firstObject;
}
- (void)insertImage:(UIImage *)image intoAssetCollection:(PHAssetCollection *)collection {
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
//This will request a PHAsset be created for the UIImage
PHAssetCreationRequest *creationRequest = [PHAssetCreationRequest creationRequestForAssetFromImage:image];
//Create a change request to insert the new PHAsset in the collection
PHAssetCollectionChangeRequest *request = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:collection];
//Add the PHAsset placeholder into the creation request.
//The placeholder is used because the actual PHAsset hasn't been created yet
if (request != nil && creationRequest.placeholderForCreatedAsset != nil) {
[request addAssets: @[creationRequest.placeholderForCreatedAsset]];
}
} completionHandler:^(BOOL success, NSError * _Nullable error) {
if (error != nil) {
NSLog(@"Error inserting image into asset collection: %@", error.localizedDescription);
}
}];
}
回答4:
Adaptation of Eddy's answer for Swift 4:
func saveImageToAlbum(_ image: UIImage, name: String) {
if let collection = fetchAssetCollection(name) {
self.saveImageToAssetCollection(image, collection: collection)
} else {
// Album does not exist, create it and attempt to save the image
PHPhotoLibrary.shared().performChanges({
PHAssetCollectionChangeRequest.creationRequestForAssetCollection(withTitle: name)
}, completionHandler: { (success: Bool, error: Error?) in
guard success == true && error == nil else {
NSLog("Could not create the album")
if let err = error {
NSLog("Error: \(err)")
}
return
}
if let newCollection = self.fetchAssetCollection(name) {
self.saveImageToAssetCollection(image, collection: newCollection)
}
})
}
}
func fetchAssetCollection(_ name: String) -> PHAssetCollection? {
let fetchOption = PHFetchOptions()
fetchOption.predicate = NSPredicate(format: "title == '" + name + "'")
let fetchResult = PHAssetCollection.fetchAssetCollections(
with: PHAssetCollectionType.album,
subtype: PHAssetCollectionSubtype.albumRegular,
options: fetchOption)
return fetchResult.firstObject
}
func saveImageToAssetCollection(_ image: UIImage, collection: PHAssetCollection) {
PHPhotoLibrary.shared().performChanges({
let creationRequest = PHAssetCreationRequest.creationRequestForAsset(from: image)
if let request = PHAssetCollectionChangeRequest(for: collection),
let placeHolder = creationRequest.placeholderForCreatedAsset {
request.addAssets([placeHolder] as NSFastEnumeration)
}
}, completionHandler: { (success: Bool, error: Error?) in
guard success == true && error == nil else {
NSLog("Could not save the image")
if let err = error {
NSLog("Error: " + err.localizedDescription)
}
return
}
})
}
回答5:
Improved version on Objective C, using blocks. It creates an album, if it doesn't exist, then saves three types of media items - photos, gifs and videos:
// Types of media, that can be saved to an album
typedef NS_ENUM(NSUInteger, AlbumMediaType) {
AlbumMediaTypePhoto,
AlbumMediaTypeGIF,
AlbumMediaTypeVideo
};
/**
Creates album if it doesn't exist and returns it in a block
*/
- (void)createCollectionOnComplete:(void (^ _Nonnull)(PHAssetCollection * _Nonnull collection))onComplete
{
NSString *albumTitle = @"YOUR_ALBUM_TITLE";
__block PHAssetCollection *collection;
__block PHObjectPlaceholder *placeholder;
// Searching for an existing album
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
fetchOptions.predicate = [NSPredicate predicateWithFormat:@"title = %@", albumTitle];
collection = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum
subtype:PHAssetCollectionSubtypeAny
options:fetchOptions].firstObject;
// If album is not found, we create it
if (!collection)
{
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
PHAssetCollectionChangeRequest *createAlbum = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:albumTitle];
placeholder = [createAlbum placeholderForCreatedAssetCollection];
} completionHandler:^(BOOL success, NSError *error) {
if (success)
{
PHFetchResult *collectionFetchResult = [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[placeholder.localIdentifier]
options:nil];
collection = collectionFetchResult.firstObject;
// After creating album, we return it
onComplete(collection);
}
}];
} else {
// If album already exists, we instantly return it
onComplete(collection);
}
}
/**
Saves an item of a given mediatype, that is located in mediaURL
*/
- (void)saveToAlbumMediaItemFromURL:(NSURL *)mediaURL mediaType:(AlbumMediaType)mediaType
{
NSData *mediaData = [NSData dataWithContentsOfURL:mediaURL];
if (!mediaData) {
OWSFail(@"%@ Could not load data: %@", self.logTag, [self.attachmentStream mediaURL]);
return;
}
[self createCollectionOnComplete:^(PHAssetCollection * _Nonnull collection) {
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
// We create a PHAsset using creationRequest
PHAssetCreationRequest *assetRequest;
switch (mediaType) {
case AlbumMediaTypePhoto: {
assetRequest = [PHAssetCreationRequest creationRequestForAssetFromImage:[UIImage imageWithData:mediaData]];
break;
}
case AlbumMediaTypeGIF: {
assetRequest = [PHAssetCreationRequest creationRequestForAsset];
PHAssetResourceCreationOptions *options = [[PHAssetResourceCreationOptions alloc] init];
[assetRequest addResourceWithType:PHAssetResourceTypePhoto data:mediaData options:options];
break;
}
case AlbumMediaTypeVideo: {
if ( !UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(mediaURL.path) ) {
OWSFail(@"%@ Could not save incompatible video data.", self.logTag);
break;
}
NSString *videoPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"file.mov"];
[mediaData writeToFile:videoPath atomically:YES];
assetRequest = [PHAssetCreationRequest creationRequestForAssetFromVideoAtFileURL:[NSURL fileURLWithPath:videoPath]];
break;
}
default:
break;
}
// Creating a request to change an album
PHAssetCollectionChangeRequest *albumChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:collection];
// PHAsset is not created yet, so we use a placeholder
PHObjectPlaceholder *placeholder = [assetRequest placeholderForCreatedAsset];
// We add a placeholder of a created item to the request of changing album
if (albumChangeRequest != nil && placeholder != nil) {
[albumChangeRequest addAssets: @[placeholder]];
}
} completionHandler:^(BOOL success, NSError *error) {
if (success) {
NSLog(@"Media item saved!");
} else {
NSLog(@"Error saving media item - %@", error ? error.localizedDescription : @"");
}
}];
}];
}
We can use these methods to save media items this way:
[self saveToAlbumMediaItemFromURL:[self.attachmentStream mediaURL] mediaType:AlbumMediaTypeGIF];
来源：https://stackoverflow.com/questions/11972185/ios-save-photo-in-an-app-specific-album