Question

我正在尝试使用AssetForURL方法，但它返回nil。

这是我正在使用的代码：

-(void)addAssetURL:(NSURL*)assetURL toAlbum:(NSString*)albumName withCompletionBlock:(SaveImageCompletion)completionBlock
{
__block BOOL albumWasFound = NO;

//search all photo albums in the library
[self enumerateGroupsWithTypes:ALAssetsGroupAlbum 
                    usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

                        //compare the names of the albums
                        if ([albumName compare: [group valueForProperty:ALAssetsGroupPropertyName]]==NSOrderedSame) {

                            //target album is found
                            albumWasFound = YES;

                            //get a hold of the photo's asset instance
                            [self assetForURL: assetURL
                                  resultBlock:^(ALAsset *asset) {
                                      //add photo to the target album
                                      [group addAsset: asset];
                                      //run the completion block
                                      completionBlock(nil);

                                  } failureBlock: completionBlock];

                            //album was found, bail out of the method
                            return;
                        }

                        if (group==nil && albumWasFound==NO) {
                            //photo albums are over, target album does not exist, thus create it

                            __weak ALAssetsLibrary* weakSelf = self;

                            //create new assets album
                            [self addAssetsGroupAlbumWithName:albumName 
                                                  resultBlock:^(ALAssetsGroup *group) {

                                                      //get the photo's instance
                                                      [weakSelf assetForURL: assetURL 
                                                                    resultBlock:^(ALAsset *asset) {

                                                                        //add photo to the newly created album
                                                                        [group addAsset: asset];

                                                                        //call the completion block
                                                                        completionBlock(nil);

                                                                    } failureBlock: completionBlock];

                                                  } failureBlock: completionBlock];

                            //should be the last iteration anyway, but just in case
                            return;
                        }

                    } failureBlock: completionBlock];

}

我给它的网址是：

    file://localhost/private/var/mobile/Applications/6630FBD3-1212-4ED0-BC3B-0C23AEEFB267/tmp/capture-T0x1d56e310.tmp.N3SZXy/capturedvideo.MOV

我从相机委托方法获取网址：

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    NSLog(@"%@",[info objectForKey:UIImagePickerControllerMediaURL]);

    [library addAssetURL:[info objectForKey:UIImagePickerControllerMediaURL] toAlbum:@"Compedia videos" withCompletionBlock:^(NSError *error) {
        if (error!=nil) {
            NSLog(@"Big error: %@", [error description]);
        }
    }];

}

有什么想法吗？

Answer 1

您确定可以访问资产库吗？别忘了检查访问状态

ALAuthorizationStatus status = [ALAssetsLibrary authorizationStatus];
if (status == ALAuthorizationStatusNotDetermined) {
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [ALAssetsLibrary authorizationStatus];
    __block BOOL accessChecked = NO; /// *stop is not respected immediately
    [library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
        if (accessChecked) return ;
        *stop = YES;
        accessChecked = YES;
    } failureBlock:^(NSError *error){
    }];
}
else {
    BOOL granted = status == ALAuthorizationStatusAuthorized;
}

- (void)enumerateGroupsWithTypes:(ALAssetsGroupType)types usingBlock:(ALAssetsLibraryGroupsEnumerationResultsBlock)enumerationBlock failureBlock:(ALAssetsLibraryAccessFailureBlock)failureBlock

描述调用给定的块作为参数传递每个   与给定资产组类型匹配的资产组。结果是   通过执行枚举块逐个传递给调用者。   此方法是异步的。枚举组时，用户可以   被要求确认申请人对数据的访问权限;方法，   但是，立即返回。你应该做你想做的任何工作   使用enumerationBlock中的资产。

如果用户拒绝访问   应用程序，或者如果不允许应用程序访问数据，   failBlock被调用。

AssetForURL返回nil

1 个答案: