ALAssetPrivate超过其拥有的ALAssetsLibrary的生命周期

Question

我试图获取photos.app中的所有图像并将它们显示在UICollectionView中.我有这个代码来检索图像:

ALAssetsLibrary *al = [ViewController defaultAssetsLibrary];

ALAssetsGroupEnumerationResultsBlock groupEnumerAtion = ^(ALAsset *result, NSUInteger index, BOOL *stop){

    if (result!=NULL) {

        if ([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]) {

            [imagesGotFromUserLibrary addObject:result];
        }

    }
};

ALAssetsLibraryGroupsEnumerationResultsBlock
libraryGroupsEnumeration = ^(ALAssetsGroup* group, BOOL* stop){
    [group setAssetsFilter:[ALAssetsFilter allPhotos]];

    if (group!=nil)
    {

        [group enumerateAssetsUsingBlock:groupEnumerAtion];
    }
    else
    {

        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            GalleryCollectionViewController *otherController = [[GalleryCollectionViewController alloc] init];
            [otherController receiveImagesWithMutableArray:imagesGotFromUserLibrary];

        });
    }

};



al = [[ALAssetsLibrary alloc] init];
[al enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos
                       usingBlock:libraryGroupsEnumeration
                     failureBlock:^(NSError *error){
                         NSLog(@"ERROR: %@", error);
                     }];

这是在viewDidLoad然后:

+ (ALAssetsLibrary *)defaultAssetsLibrary {
static dispatch_once_t pred = 0;
static ALAssetsLibrary *library = nil;
dispatch_once(&pred, ^{
    library = [[ALAssetsLibrary alloc] init];
});
return library;
}

这段代码将一个数组发送到另一个控制器,该控制器将图像设置为我的UICollectionView.问题是我收到错误"无法尝试访问其拥有的ALAssetsLibrary的生命周期",如果我尝试NSLog我的数组,结果类似于"ALAsset - Type:Unknown,URL:(null)".

我抬头看了互联网,找到了解决方案.我应该添加这行代码,但它不起作用.代码是:

+ (ALAssetsLibrary *)defaultAssetsLibrary {
static dispatch_once_t pred = 0;
static ALAssetsLibrary *library = nil;
dispatch_once(&pred, ^{
    library = [[ALAssetsLibrary alloc] init];
});
return library;
}

任何人都能帮助我获取正确的图像URL显示？

Answer 1

解决方案是始终使用相同的库来访问所有类中的资产.您在上面显示的单例解决方案很好 - 只要您的所有类都调用defaultAssetsLibrary它们,并且它们都不会分配/初始化它们自己的类ALAssetsLibrary.