iOS 14使用PHPhotoLibrary获取图片库

之前项目使用UIImagePickerController获取相册。由于iOS 14升级了图片库权限，多了PHAuthorizationStatusLimited权限。为了适应升级，需要用PHPhotoLibrary获取相册。

一、使用PHPickerViewController显示图片库

<PhotosUI/PhotosUI.h>中提供了PHPickerViewController。可以直接使用，用于显示照片库。带原生的搜索功能（很强大）。但是Limited权限，显示全部照片而非部分。

@interface PHPickerViewController : UIViewController
/// The delegate to be notified.
@property (NS_NONATOMIC_IOSONLY, weak) id<PHPickerViewControllerDelegate> delegate NS_REFINED_FOR_SWIFT;
/// Initializes new picker with the \c configuration the picker should use.
- (instancetype)initWithConfiguration:(PHPickerConfiguration *)configuration NS_DESIGNATED_INITIALIZER NS_REFINED_FOR_SWIFT;
@end

1.先声明PHPickerConfiguration

@interface PHPickerConfiguration : NSObject <NSCopying>
//转码模式
@property (NS_NONATOMIC_IOSONLY) PHPickerConfigurationAssetRepresentationMode preferredAssetRepresentationMode;
//可选择的照片数
@property (NS_NONATOMIC_IOSONLY) NSInteger selectionLimit;
//筛选模式设置，目前可以指定筛选照片、视频、LivePhoto 几种类型，或者任何他们的组合。
@property (NS_NONATOMIC_IOSONLY, copy, nullable) PHPickerFilter *filter;
@end

2.使用Delegate获取照片

@protocol PHPickerViewControllerDelegate <NSObject>
- (void)picker:(PHPickerViewController *)picker didFinishPicking:(NSArray<PHPickerResult *> *)results;
@end

3.代码

//跳转代码
PHPickerConfiguration *config = [[PHPickerConfiguration alloc] initWithPhotoLibrary:[PHPhotoLibrary sharedPhotoLibrary]];
config.filter = [PHPickerFilter imagesFilter];
config.selectionLimit = 1;
self.pickerVC = [[PHPickerViewController alloc] initWithConfiguration:config];
self.pickerVC.delegate = self;
self.pickerVC.modalPresentationStyle = UIModalPresentationFullScreen;
[self presentViewController:self.pickerVC animated:YES completion:^{}];


//代理
- (void)picker:(PHPickerViewController *)picker didFinishPicking:(NSArray<PHPickerResult *> *)results
{
    if (results.count<=0) {//点击返回
        
    }else{
        PHPickerResult *imgResult = [results objectAtIndex:0];//可多选
        if ([imgResult.itemProvider canLoadObjectOfClass:UIImage.class]) {
            [imgResult.itemProvider loadObjectOfClass:[UIImage class] completionHandler:^(__kindof id<NSItemProviderReading>  _Nullable object, NSError * _Nullable error) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    UIImage *image = object;
                });
            }];
        }
    }
    [self.pickerVC dismissViewControllerAnimated:YES completion:nil];
}

二、使用PHFetchResult获取图片

PHFetchResult可以获取到有限照片库权限的照片。如果此时权限是全部，则返回全部照片。这种方法只能自己写UI去显示。

1.获取相册数据

1.1PHFetchResult

// Accessing fetched results (fetches objects from the backing store in chunks on demand rather than all at once)
// Fetched objects will be kept in a cache and purged under memory pressure
//访问获取的结果（按需从备份存储中获取对象，而不是一次获取所有对象）
//获取的对象将保存在缓存中，并在内存压力下清除

PHFetchResult *smartAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeSmartAlbumUserLibrary options:nil];

其中PHAssetCollection一个该实例对象代表一个相册。是PHCollection的子类。

typedef NS_ENUM(NSInteger, PHAssetCollectionType) {
 PHAssetCollectionTypeAlbum      = 1,照片应用程序中的相册 //An album in the Photos app. 
 PHAssetCollectionTypeSmartAlbum = 2,内容动态更新的智能相册。//  A smart album whose contents update dynamically.
 PHAssetCollectionTypeMoment   API_DEPRECATED("Will be removed in a future release", ios(8, 13), tvos(10, 13)) = 3, // A moment in the Photos app.
 }

PHAssetCollectionSubtype
1.User Album Types

 // PHAssetCollectionTypeAlbum regular subtypes
 PHAssetCollectionSubtypeAlbumRegular         = 2, 在iPhone中自己创建的相册// An album created in the Photos app. 
 PHAssetCollectionSubtypeAlbumSyncedEvent     = 3, 从iPhoto（就是iMac上的图片app）中导入图片到设备//An Event synced to the device from iPhoto.
 PHAssetCollectionSubtypeAlbumSyncedFaces     = 4, 从图片app中导入的人物照片// A Faces group synced to the device from iPhoto.
 PHAssetCollectionSubtypeAlbumSyncedAlbum     = 5, 从图片app导入的相册// An album synced to the device from iPhoto. 
 PHAssetCollectionSubtypeAlbumImported        = 6, 从其他的相机或者存储设备导入的相册// An album imported from a camera or external storage.

2.Cloud Album Types

// PHAssetCollectionTypeAlbum shared subtypes
PHAssetCollectionSubtypeAlbumMyPhotoStream   = 100,  用户的照片流，如果在设置里关闭了iCloud开关，就获取不到了。//The user’s personal iCloud Photo Stream.
PHAssetCollectionSubtypeAlbumCloudShared     = 101,  iCloud的共享相册，点击照片上的共享tab创建后就能拿到了，但是前提是你要在设置中打开iCloud的共享开关（打开后才能看见共享tab）// An iCloud Shared Photo Stream.

3.Smart Album Types

 // PHAssetCollectionTypeSmartAlbum subtypes
 PHAssetCollectionSubtypeSmartAlbumGeneric    = 200,一个没有更多特定子类型的智能相册。//A smart album of no more specific subtype.
 PHAssetCollectionSubtypeSmartAlbumPanoramas  = 201,  一个智能相册，将照片库中的所有全景照片分组。// A smart album that groups all panorama photos in the photo library.
 PHAssetCollectionSubtypeSmartAlbumVideos     = 202, 将照片库中的所有视频资产分组的智能相册。//A smart album that groups all video assets in the photo library.
 PHAssetCollectionSubtypeSmartAlbumFavorites  = 203,  标记为喜欢、收藏 //A smart album that groups all assets that the user has marked as favorites.
 PHAssetCollectionSubtypeSmartAlbumTimelapses = 204, 延时拍摄、定时拍摄// A smart album that groups all time-lapse videos in the photo library. 
 PHAssetCollectionSubtypeSmartAlbumAllHidden  = 205,   一个智能相册，将照片应用程序的“时刻”视图中隐藏的所有资产分组。//A smart album that groups all assets hidden from the Moments view in the Photos app.
 PHAssetCollectionSubtypeSmartAlbumRecentlyAdded = 206, 最近添加的 //A smart album that groups assets that were recently added to the photo library.
 PHAssetCollectionSubtypeSmartAlbumBursts     = 207,  连拍//A smart album that groups all burst photo sequences in the photo library. 
 PHAssetCollectionSubtypeSmartAlbumSlomoVideos = 208,  所有慢镜头视频// A smart album that groups all Slow-Mo videos in the photo library.
 PHAssetCollectionSubtypeSmartAlbumUserLibrary = 209, 一个智能相册，它将来自用户自己库的所有资产（与iCloud共享相册中的资产不同）。//A smart album that groups all assets that originate in the user’s own library (as opposed to assets from iCloud Shared Albums).
 PHAssetCollectionSubtypeSmartAlbumSelfPortraits = 210, 使用前置摄像头拍摄的作品 //A smart album that groups all photos and videos captured using the device’s front-facing camera.
 PHAssetCollectionSubtypeSmartAlbumScreenshots = 211,  屏幕截图 //A smart album that groups all images captured using the device’s screenshot function.
 PHAssetCollectionSubtypeSmartAlbumDepthEffect = 212,  在可兼容的设备上使用景深模式拍的照片（人像模式） //A smart album that groups all images captured using the Depth Effect camera mode on compatible devices.
 PHAssetCollectionSubtypeSmartAlbumLivePhotos = 213,  Live Photo资源 //A smart album that groups all Live Photo assets.
 PHAssetCollectionSubtypeSmartAlbumAnimated = 214,  将所有图像动画资源分组的智能相册。//A smart album that groups all image animation assets.
 PHAssetCollectionSubtypeSmartAlbumLongExposures = 215,  启用长曝光变化的所有Live Photo资源 //A smart album that groups all Live Photo assets where the Long Exposure variation is enabled. 
 // Used for fetching, if you don't care about the exact subtype
 PHAssetCollectionSubtypeAny = NSIntegerMax

2.实现代码

2.1获取所有照片

PHFetchOptions *option = [[PHFetchOptions alloc] init];
//ascending 为YES时，按照照片的创建时间升序排列;为NO时，则降序排列
option.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
self.fetchList = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:option];//PHFetchResult这个类型可以当成NSArray使用。此时所有可获取照片都已拿到，可以刷新UI进行显示

2.2按顺序获取照片显示

PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
    options.synchronous = true;
    options.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
    options.networkAccessAllowed = YES;
    [[PHImageManager defaultManager] requestImageDataAndOrientationForAsset:[self.fetchList objectAtIndex:indexPath.row] options:options resultHandler:^(NSData * _Nullable imageData, NSString * _Nullable dataUTI, CGImagePropertyOrientation orientation, NSDictionary * _Nullable info)
    {
        UIImage *image = [UIImage imageWithData:imageData];
    }];

参考：
1.照片框架 https://objccn.io/issue-21-4/
2.Photo Frameworks之PHAssetCollection、PHCollectionList和PHAsset https://www.jianshu.com/p/ac3d7f490f82