照片框架PhotoKit使用记录

1、创建自定义相册并命名

- (PHAssetCollection * )createCollection{
    // 创建一个新的相册，查看所有的自定义相册，先查看是否有自己要创建的自定义相册，如果没有自己要创建的自定义相册那么我们就进行创建
    NSString * title = [NSBundle mainBundle].infoDictionary[(NSString *)kCFBundleNameKey];
    PHFetchResult<PHAssetCollection *> *collections =  [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    
    PHAssetCollection * createCollection = nil; // 最终要获取的自己创建的相册
    for (PHAssetCollection * collection in collections) {
        if ([collection.localizedTitle isEqualToString:title]) {    // 如果有自己要创建的相册
            createCollection = collection;
            break;
        }
    }
    if (createCollection == nil) {  // 如果没有自己要创建的相册
        // 创建自己要创建的相册
        NSError * error1 = nil;
        __block NSString * createCollectionID = nil;
        // 这个方法会在相册创建完毕后才会返回(同步返回)
        [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
            NSString * title = [NSBundle mainBundle].infoDictionary[(NSString *)kCFBundleNameKey];
            createCollectionID = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title].placeholderForCreatedAssetCollection.localIdentifier;
        } error:&error1];
        
        if (error1) {
            NSLog(@"创建相册失败...");
        }
        // 创建相册之后我们还要获取此相册  因为我们要往进存储相片
        createCollection = [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[createCollectionID] options:nil].firstObject;
    }
    
    return createCollection;
}

2、保存图片至相册

- (void)saveImage:(UIImage *)image toCollection:(PHAssetCollection *)collection {
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        // 保存图片至相机胶卷 并拿到这个图片资源的标识
        PHAssetChangeRequest *createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
        PHObjectPlaceholder *assetPlaceholder = createAssetRequest.placeholderForCreatedAsset;
        // 将“相机胶卷”中的图片添加到指定相册
        PHAssetCollectionChangeRequest *albumChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:collection];
        [albumChangeRequest addAssets:@[assetPlaceholder]];
    } completionHandler:^(BOOL success, NSError * _Nullable error) {
        if (error) {
            NSLog(@"success = %d, error = %@", success, error);
        }
    }];
}

3、从指定相册读取照片资源

- (PHFetchResult *)getImagesFromCollection:(PHAssetCollection *)collection {
    // 获取所有资源的集合，并按资源的创建时间逆序排序
    PHFetchOptions *options = [[PHFetchOptions alloc] init];
    // 根据照片创建时间来倒序排列
    options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
    PHFetchResult *result = [PHAsset fetchAssetsInAssetCollection:collection options:options];
    return result;
}

4、删除指定相册的指定图片

- (void)removeAsset:(PHAsset *)asset fromCollection:(PHAssetCollection *)collection {
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        // 将指定相册的指定图片移除（这里只是把照片从相册中移除，照片依然存储在手机的相册胶卷中）
        PHAssetCollectionChangeRequest *albumChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:collection];
        [albumChangeRequest removeAssets:@[asset]];
        // 将“相机胶卷”中的指定图片删除掉
        [PHAssetChangeRequest deleteAssets:@[asset]];
    } completionHandler:^(BOOL success, NSError * _Nullable error) {
        if (error) {
            NSLog(@"success = %d, error = %@", success, error);
        }
    }];
}

5、将相册中的照片资源转化为可用的image

PHFetchResult *result = [self getImagesFromCollection:_selfCollection];
    [result enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        PHImageRequestOptions *option = [[PHImageRequestOptions alloc] init];
        option.resizeMode = PHImageRequestOptionsResizeModeNone;
        // 照片是否同步处理图像请求，设置为NO可能会多次调用resultHandle，设置为YES会阻塞调用线程直到图像数据准备好了或出现错误
        option.synchronous = NO;
        // targetSize设置为PHImageManagerMaximumSize，则image会返回原始尺寸
        [[PHImageManager defaultManager] requestImageForAsset:(PHAsset *)obj targetSize:PHImageManagerMaximumSize contentMode:PHImageContentModeAspectFit options:option resultHandler:^(UIImage * _Nullable imgResult, NSDictionary * _Nullable info) {
            // 是否原图
            BOOL isOriginImg = ![[info objectForKey:PHImageCancelledKey] boolValue] && ![info objectForKey:PHImageErrorKey] && ![[info objectForKey:PHImageResultIsDegradedKey] boolValue];

            if (isOriginImg) {
                // do something you want to do with UIImage
            }
        }];
    }];