ios - [PHCollectionList canContainCustomKeyAssets] : unrecognized selector sent to instance

Question

在最新版本的 iOS(iOS 9.2 和 iOS 9.3)上，获取 PHAssets 现在崩溃了。它以前工作正常。

我得到的错误是:

[PHCollectionList canContainCustomKeyAssets]: unrecognized selector sent to instance Terminating app due to uncaught exception 'NSInvalidArgumentException'

抛出异常的行是:

            PHFetchResult *fetchImage = [PHAsset fetchKeyAssetsInAssetCollection:(PHAssetCollection*)collection options:fetchOptions];

更多代码，供引用:

Class PHPhotoLibrary_class = NSClassFromString(@"PHPhotoLibrary");
        if (PHPhotoLibrary_class) {

            PHFetchResult *fetchResult = self.collectionsFetchResults[indexPath.section];
            PHCollection *collection = fetchResult[indexPath.row];

            cell.textLabel.text = collection.localizedTitle;

            PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
            fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
            PHFetchResult *fetchImage = [PHAsset fetchKeyAssetsInAssetCollection:(PHAssetCollection*)collection options:fetchOptions];
            PHAsset *asset = [fetchImage firstObject];

            PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
            options.resizeMode = PHImageRequestOptionsResizeModeExact;

            CGFloat scale = [UIScreen mainScreen].scale;
            CGFloat dimension = 90.0;
            CGSize size = CGSizeMake(dimension*scale, dimension*scale);

            [[PHImageManager defaultManager] requestImageForAsset:asset
                                                       targetSize:size
                                                      contentMode:PHImageContentModeAspectFill
                                                          options:options
                                                    resultHandler:^(UIImage *result, NSDictionary *info) {
                                                        if (result) {
                                                            CGSize itemSize = CGSizeMake(60, 60);
                                                            UIGraphicsBeginImageContextWithOptions(itemSize, NO, 2);
                                                            CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
                                                            [result drawInRect:imageRect];
                                                            cell.imageView.image  = UIGraphicsGetImageFromCurrentImageContext();
                                                            UIGraphicsEndImageContext();
                                                        }
                                                        else{
                                                            UIImage *placeholder = [UIImage imageNamed:@"image-placeholder.jpg"];
                                                            CGSize itemSize = CGSizeMake(60, 60);
                                                            UIGraphicsBeginImageContextWithOptions(itemSize, NO, 2);
                                                            CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
                                                            [placeholder drawInRect:imageRect];
                                                            cell.imageView.image  = UIGraphicsGetImageFromCurrentImageContext();
                                                            UIGraphicsEndImageContext();
                                                        }
                                                    }];
        }

Answer 1

这个问题其实出在这里:

PHCollection *collection = fetchResult[indexPath.row];

然后在这里:

PHAsset *asset = [fetchImage firstObject];

您正在使用 PHCollection 获取集合，然后假设所有 Assets 都是 PHAssets 而没有正确检查是否是这种情况。

实际上，PHCollection 有 two possible subclasses : PHAsset 和 PHCollectionList，而 PHCollectionList 是这里引发错误的原因。

在 PHCollection *collection = fetchResult[indexPath.row]; 之后包装代码并检查 PHAsset，它应该可以解决问题:

if ([collection isKindOfClass:[PHAssetCollection class]]) {
//code 
}