ios - ALAsset 图像为空

Question

我正在从库中获取 ALAsset，但是当我尝试设置 UIImageView 时，UIImage 为 nil。

    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library assetForURL:[NSURL URLWithString:entityObject.localUrl] resultBlock:^(ALAsset *asset) {
        if (asset) {
            ALAssetRepresentation *representation = [asset defaultRepresentation];
            imageView.image = [UIImage imageWithCGImage:representation.fullResolutionImage
                                       scale:[representation scale]
                                 orientation:(UIImageOrientation)[representation orientation]];

            NSLog(@"imageView.image: %@",imageView.image); // imageView.image: (null)
            NSLog(@"image size %f", imageView.image.size.width); //image size: 0.000000
            imageView.frame = CGRectMake(imageView.frame.origin.x, imageView.frame.origin.y, imageView.image.size.width, imageView.image.size.height);

        } else {
            NSLog(@"test not found?");
        }
    } failureBlock:^(NSError *error) {
        NSLog(@"FAILED TO FIND %@", error);
    }];

知道我做错了什么吗？

Answer 1

您的代码看起来很棒，这让我怀疑问题出在您没有注意的地方 - 也就是说，imageView 本身可能是 nil。这会导致 imageView.image 为 nil，因此您认为对 [UIImage imageWithCGImage...] 的调用失败了。但事实并非如此!

这里的寓意是:多解开你的代码。你写了这个:

imageView.image = [UIImage imageWithCGImage:representation.fullResolutionImage
                                   scale:[representation scale]
                             orientation:(UIImageOrientation)[representation orientation]];

这就是隐藏真正问题的原因。要是你写了这个就好了:

UIImage* image = [UIImage imageWithCGImage:representation.fullResolutionImage
                                   scale:[representation scale]
                             orientation:(UIImageOrientation)[representation orientation]];
NSLog(@"%@", image);
imageView.image = image;
// ...

... 很明显您已成功从 Assets 中获取图像，但是当您尝试将其分配给 ImageView 时， ImageView 不在那里接收它，这就是球掉了。