ALAssetsLibrary delete ALAssetsGroup / ALAsset

问题:

I have created "photos album" from my App, using IOS AssetsLibrary.

Reading ALAssetsLibrary,ALAssetsGroup and ALAsset documentations, i have seen methods to "addAsset","addAssetsGroupAlbumWithName".

Is there a way to delete PROGRAMMATICALLY my ALAssetsGroup and ALAsset. (the property 'editable' suppose to be TRUE because i create this data).

回答1:

This is not possible using any documented API. Only the photos app can delete Albums. If you want this feature to be added to iOS, I would fill a feature request at http://radar.apple.com.

回答2:

You can only delete the ALAsset which is created by your app with document API [ALAsset setImageData:metadata:completionBlock:] (But I have not found any API to delete a ALAssetGroup).

1). Add an image "photo.jpg" to your project 2). Save an image to asset library:

ALAssetsLibrary *lib = [ALAssetsLibrary new];
UIImage *image = [UIImage imageNamed:@"photo.jpg"];
[lib writeImageToSavedPhotosAlbum:image.CGImage metadata:@{} completionBlock:^(NSURL *assetURL, NSError *error) {
    NSLog(@"Write image %@ to asset library. (Error %@)", assetURL, error);
}];

3). Go to default gallery, you will find photo.jpg in your "Saved Photos" album.

4). Delete this image from asset library:

ALAssetsLibrary *lib = [ALAssetsLibrary new];
[lib enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
    [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop) {
        if(asset.isEditable) {
            [asset setImageData:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
                NSLog(@"Asset url %@ should be deleted. (Error %@)", assetURL, error);
            }];
        }
    }];
} failureBlock:^(NSError *error) {

}];

5). Go to default gallery, you will find photo.jpg has already been deleted.

回答3:

in ios8 deleting photos might be possible using the Photos Framework

Please check the documentation of Photos Framework

For deleting assets refer to PHAssetChangeRequest

+ (void)deleteAssets:(id<NSFastEnumeration>)assets

where assets is an array of PHAsset objects to be deleted.

For deleting collections refer to PHAssetCollectionChangeRequest

+ (void)deleteAssetCollections:(id<NSFastEnumeration>)assetCollections

https://developer.apple.com/library/prerelease/ios/documentation/Photos/Reference/PHAssetChangeRequest_Class/index.html#//apple_ref/occ/clm/PHAssetChangeRequest/deleteAssets:

回答4:

As Ted said, this is now possible in iOS 8 using the Photos service. It's pretty clean actually. You need to submit a change request to the photolibrary. Here's an example.

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    [PHAssetChangeRequest deleteAssets:arrayOfPHAssets];
} completionHandler:^(BOOL success, NSError *error) {
    NSLog(@"Finished deleting asset. %@", (success ? @"Success." : error));
}];

Make sure you've imported Photos, and gotten authorization from the user. (Which you probably did to show the image already)

PHAssetchangeRequest - deleteAssets https://developer.apple.com/library/prerelease/ios/documentation/Photos/Reference/PHAssetChangeRequest_Class/index.html#//apple_ref/occ/clm/PHAssetChangeRequest/deleteAssets: PHPhotoLibrary Class - authorizationStatus https://developer.apple.com/library/ios/documentation/Photos/Reference/PHPhotoLibrary_Class/#//apple_ref/occ/clm/PHPhotoLibrary/authorizationStatus

回答5:

evanchin is correct. Further more, if you want to do this in Xamarin.iOS (aka monotouch):

var lib = new ALAssetsLibrary();
lib.Enumerate(ALAssetsGroupType.All, (ALAssetsGroup group, ref bool libStop) =>
{
    if (group == null)
    {
        return;
    }
    group.Enumerate((ALAsset asset, int index, ref bool groupStop) =>
    {
        if (asset != null && asset.Editable)
        {
            asset.SetImageDataAsync(new NSData(IntPtr.Zero), new NSDictionary(IntPtr.Zero));
        }
    });
}, error => { });

This code will delete all images that your app added to the ALAssetsLibrary.

回答6:

You may delete any asset in the library using documented API ONLY.

1. over writing the [ALAsset isEditable] function:

   @implementation ALAsset(DELETE)
   -(BOOL)isEditable{
       return YES;
   }
   @end
   

2. like evanchin said, delete the asset:

   ALAssetsLibrary *lib = [ALAssetsLibrary new];
   [lib enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos 
                      usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
       [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop) {
           if(asset.isEditable) {
               [asset setImageData:nil 
                          metadata:nil 
                   completionBlock:^(NSURL *assetURL, NSError *error) {
                   NSLog(@"Asset url %@ should be deleted. (Error %@)", assetURL, error);
               }];
            }
        }];
    } failureBlock:^(NSError *error) {
   
    }];