Photos 框架實踐以及坑

PhotoManager.h

#import <Foundation/Foundation.h>
#import <Photos/Photos.h>

@interface PhotoManager : NSObject

/** 獲取單例對象 PhotoManager */
+ (instancetype)sharedManager;

/** 讀取所有相冊的信息 返回數(shù)組<AlbumModel *> */
- (void)loadAlbumInfoWithCompletionBlock:(void(^)(NSArray * albumsModelArray))completionBlock;

/** 讀取某個asset的圖片*/
- (void)getThumbnailImageWithAsset:(PHAsset *)asset completionBlock:(void(^)(UIImage *thumbnail))completionBlock;

/** 讀取預覽圖片 屏幕的大小*/
- (void)getPreviewImageWithAsset:(PHAsset *)asset completionBlock:(void(^)(UIImage *result))completionBlock;

/** 讀取原圖圖片 */
- (void)getOriginImageWithAsset:(PHAsset *)asset completionBlock:(void(^)(UIImage *result))completionBlock;
@end

PhotoManager.m

#import "PhotoManager.h"
#import "AlbumModel.h"

@interface PhotoManager ()
@property (nonatomic, strong) PHCachingImageManager *cacheImageManager;
@end

@implementation PhotoManager

+ (instancetype)sharedManager{
    static PhotoManager *instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[PhotoManager alloc] init];
    });
    
    return instance;
}

- (void)loadAlbumInfoWithCompletionBlock:(void (^)(NSArray *))completionBlock{
    //用來存放每個相冊model
    NSMutableArray *albumModelsArray = [NSMutableArray array];
    
    //創(chuàng)建讀取哪些相冊的subType
    PHAssetCollectionSubtype subType = PHAssetCollectionSubtypeSmartAlbumVideos|PHAssetCollectionSubtypeSmartAlbumUserLibrary|PHAssetCollectionSubtypeSmartAlbumScreenshots;
    
    //1.獲取所有相冊的信息PHFetchResult<PHAssetCollection *>
    PHFetchResult *albumsCollection = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:subType options:nil];
    
    //2.遍歷albumsCollection獲取每一個相冊的具體信息
    [albumsCollection enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        //將obj轉化為某個具體類型 PHAssetCollection 代表一個相冊
        PHAssetCollection *collection = (PHAssetCollection *)obj;
        
        //創(chuàng)建讀取相冊信息的options
        PHFetchOptions *options = [[PHFetchOptions alloc] init];
        options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
        
        //讀取相冊里面的所有信息 PHFetchResult <PHAsset *>
        PHFetchResult *assetsResult = [PHAsset fetchAssetsInAssetCollection:collection options:options];
        
        if (assetsResult.count > 0) {
            //創(chuàng)建一個model封裝這個相冊的信息
            AlbumModel *model = [[AlbumModel alloc] init];
            model.albumName = collection.localizedTitle;//相冊名
            model.count = assetsResult.count; //相冊里面內(nèi)容的個數(shù)（多少圖片或者視頻）
            model.result = assetsResult; //保存這個相冊的內(nèi)容
            
            [albumModelsArray addObject:model];
        }
       
    }];
    
    //回調(diào)
    //completionBlock ? completionBlock(albumModelsArray) : nil;
    if (completionBlock != nil) {
        completionBlock(albumModelsArray);
    }
}

- (PHCachingImageManager *)cacheImageManager{
    if (_cacheImageManager == nil) {
        self.cacheImageManager = [[PHCachingImageManager alloc] init];
    }
    return _cacheImageManager;
}

- (void)getThumbnailImageWithAsset:(PHAsset *)asset completionBlock:(void (^)(UIImage *))completionBlock{
    
    //創(chuàng)建異步讀取圖片的選項options
    PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
    options.resizeMode = PHImageRequestOptionsResizeModeFast;
    options.synchronous = NO;
    
    CGFloat scale = [UIScreen mainScreen].scale;
    [self.cacheImageManager requestImageForAsset:asset targetSize:CGSizeMake(70*scale, 70*scale) contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
        //回調(diào)讀取的圖片
        completionBlock ? completionBlock(result) : nil;
    }];
}

- (void)getPreviewImageWithAsset:(PHAsset *)asset completionBlock:(void (^)(UIImage *))completionBlock{
    //創(chuàng)建異步讀取圖片的選項options
    PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
    options.resizeMode = PHImageRequestOptionsResizeModeFast;
    options.synchronous = NO;
    
    CGFloat scale = [UIScreen mainScreen].scale;
    CGSize screenSize = [UIScreen mainScreen].bounds.size;
    
    [self.cacheImageManager requestImageForAsset:asset targetSize:CGSizeMake(screenSize.width*scale, screenSize.height*scale) contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
        //回調(diào)讀取的圖片
        completionBlock ? completionBlock(result) : nil;
    }];

}

- (void)getOriginImageWithAsset:(PHAsset *)asset completionBlock:(void (^)(UIImage *))completionBlock{
    //創(chuàng)建異步讀取圖片的選項options
    PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
    options.synchronous = NO;
    
    [self.cacheImageManager requestImageForAsset:asset targetSize:PHImageManagerMaximumSize contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
        //回調(diào)讀取的圖片
        completionBlock ? completionBlock(result) : nil;
    }];
}
@end

新寫了一個項目，安利一下！還在用UIImagePickerController? ——iOS相冊選擇器