ALAssetRepresentation fullResolutionImage永远不会返回

Question

我正在编写一个多线程应用程序,需要在后台集中上传ALAssetsLibrary中的照片.所以我有一个NSOperation子类,它通过资产的URL找到适当的ALAsset,并将图像添加到上传队列.

在当前ALAsset的上传队列中,我需要从图像中获取元数据,但是我遇到了一个问题:在ALAsset的ALAssetRepresentation上调用它们时,-metadata和-fullResolutionImage方法都不会返回.他们只是无限期地挂在那里.我尝试在LLDB中打印这些方法中的每一个的值,但它挂起了调试器,我最终杀死了Xcode,信号9样式.在后台队列上调用这些方法.

我在iPad 2上测试这些.这是在-assetForURL的成功块中找到ALAsset时添加到上传队列的方法:resultBlock:failureBlock:

- (void)addMediaToUploadQueue:(ALAsset *)media {
    @autoreleasepool {
        ALAssetRepresentation *defaultRepresentation = [media defaultRepresentation];
        CGImageRef fullResolutionImage = [defaultRepresentation fullResolutionImage];

        // Return if the user is trying to upload an image which has already been uploaded
        CGFloat scale = [defaultRepresentation scale];
        UIImageOrientation orientation = [defaultRepresentation orientation];

        UIImage *i = [UIImage imageWithCGImage:fullResolutionImage scale:scale orientation:orientation];
        if (![self isImageUnique:i]) return;

        NSDictionary *imageDictionary = [self dictionaryForAsset:media withImage:i];

        dispatch_async(self.background_queue, ^{
            NSManagedObjectContext *ctx = [APPDELEGATE createManagedObjectContextForThread];
            [ctx setUndoManager:nil];

            [ctx performBlock:^{
                ImageEntity *newImage = [NSEntityDescription insertNewObjectForEntityForName:@"ImageEntity"
                                                                    inManagedObjectContext:ctx];

                [newImage updateWithDictionary:imageDictionary
                         inManagedObjectContext:ctx];

                [ctx save:nil];

                [APPDELEGATE saveContext];

                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.fetchedResultsController performFetch:nil];
                });

                    if (!currentlyUploading) {
                        currentlyUploading = YES;
                        [self uploadImage:newImage];
                    }
            }];
        });
    }
}

Answer 1

我有一个类似的问题,我正在试图弄清楚我的头发.

事实证明我为ALAssetsLibrary设置了一个单例,我的代码没有正确调用它,一些ALAssets返回一个空的'fullResolutionImage'

在我的所有NSLog中,我一定错过了Xcode最重要的消息:

"无法尝试在其拥有的ALAssetsLibrary的生命周期内访问ALAssetPrivate"

点击此链接

http://www.daveoncode.com/2011/10/15/solve-xcode-error-invalid-attempt-to-access-alassetprivate-past-the-lifetime-of-its-owning-alassetslibrary/

我希望有所帮助