PHAssetResourceManager 用法？

Question

我正在尝试使用 PHAssetResourceManager 从资产中获取数据。

我在任何地方都找不到关于此的任何示例。

我曾经使用 PHImageManager 但我的应用要到明年才会发布所以我想到那个时候大多数人很可能已经采用了最新的 iOS 无论如何都是版本。

尝试记录指定资产的资源时 returns“0”下方的代码。

如何使用 PHAssetResourceManager？

我的代码：

    PHFetchOptions *fetchOptions;
    fetchOptions.sortDescriptors = @[ [NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES], ];
    PHFetchResult *fetchResult = [PHAsset fetchAssetsWithOptions:fetchOptions];

    NSLog(@"fetchResult.count = %lu", fetchResult.count);

    PHAsset *asset = [fetchResult objectAtIndex: assetIndex];

    NSArray *resourceArray = [PHAssetResource assetResourcesForAsset: asset];

    NSLog(@"resourceArray.count = %lu", resourceArray.count); //<<< returns 0?

    PHAssetResource *ar = [resourceArray objectAtIndex: 0];
    PHAssetResourceRequestOptions *arro = [[PHAssetResourceRequestOptions alloc] init];


    PHAssetResourceManager *arm = [PHAssetResourceManager defaultManager];


    [arm requestDataForAssetResource:ar options:arro
        dataReceivedHandler:^(NSData *assetData){
            NSLog(@"extractData dataReceivedHandler: %lu", assetData.length);
        }

        completionHandler:^(NSError *error){
            NSLog(@"extractData Error: %@", error);

        }
     ];
});

Answer 1

我从模拟器中的视图控制器 viewDidLoad 方法调用以下方法，一切正常。

- (void)readAsset:(NSInteger)assetIndex {
    PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
    fetchOptions.sortDescriptors = @[ [NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES] ];
    PHFetchResult *fetchResult = [PHAsset fetchAssetsWithOptions:fetchOptions];

    if (assetIndex < fetchResult.count) {
        PHAsset *asset = fetchResult[assetIndex];
        NSArray *resourceArray = [PHAssetResource assetResourcesForAsset: asset];
        PHAssetResource *assetResource = resourceArray[0];

        PHAssetResourceManager *arm = [PHAssetResourceManager defaultManager];
        [arm requestDataForAssetResource:assetResource options:nil dataReceivedHandler:^(NSData * _Nonnull data) {
            NSLog(@"data.length = %lu", (unsigned long)data.length);
        } completionHandler:^(NSError * _Nullable error) {
            NSLog(@"error = %@", error);
        }];
    }
    else {
        NSLog(@"no such asset.");
    }
}

输出是：

fetchResult.count = 5
data.length = 1048576
data.length = 1048576
data.length = 507598
data.length = 0
error = (null)

你能找出你的代码和我的代码有什么不同吗？我唯一看到的是你在使用它之前没有创建 PHFetchOptions 对象。那是未定义的行为。

PHAssetResourceManager 用法？

PHAssetResourceManager usage?

cocoa-touch

ios9

assets

fetch