Question

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

我找不到任何关于此的例子。

我曾经使用PHImageManager但我的应用程序要到明年才会发布所以到那时我猜大多数人很可能会采用最新的 iOS版本无论如何。

尝试记录指定资产的资源时，以下代码返回“0”。

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.");
    }
}

输出结果为：

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

你能弄清楚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之前不创建PHFetchOptions对象。这是未定义的行为。

PHAssetResourceManager用法？

1 个答案: