Question

我从库中获取ALAsset，但当我尝试设置UIImageView时，UIImage为零。

    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？

Answer 1

这样对我有用：

ALAssetsLibrary *library = [self defaultAssetsLibrary];
[library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
    [group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {

        if(result)
        {
            ALAssetRepresentation *representation = [result 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);

        }
    }];

} failureBlock:^(NSError *error) {
    NSLog(@"Error loading images %@", error);
}];

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

Answer 2

你的代码看起来很棒，这让我怀疑问题是你看不到的地方 - 也就是说，imageView本身可能是零。这会导致imageView.image为零，因此您可能会想到对[UIImage imageWithCGImage...]的调用失败。但事实并非如此！

这里的道德是：更多地解开你的代码。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。如果你只写了这个：

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

...很明显你是从资产中成功获取图像，但是当你试图将它分配给图像视图时，图像视图就不能接收它了，那就是球落了下来。

ALAsset图像为空

2 个答案: