c# - 如何在 Xamarin.iOS 中从 URL 加载图像

Question

当我从画廊中挑选一张图片时，我有这样的东西:

NSUrl referenceURL = e.Info[new  
NSString("UIImagePickerControllerReferenceURL")] as NSUrl;
//imageURL = referenceURL.AbsoluteString;
imageURL = referenceURL.AbsoluteUrl.ToString();
string path = referenceURL.Path;

NSUrl url1 = referenceURL.FilePathUrl;
NSUrl url2 = referenceURL.FileReferenceUrl;

现在我正尝试从 URL 加载该图像:

var url = new NSUrl(imageURL);
var data = NSData.FromUrl(url);
defectImage.Image = UIImage.LoadFromData(data);

但是 data 仍然是 null。

从 URL 加载图像的正确方法是什么？

注意:url1 和 url2 只是示例。path 类似于 = "/imagename.jpg"

也许我检索 URL 的方式有误？获取路径/url 的方法有很多。

Answer 1

由于这些图片 url 是基于“assets-library”的，因此您需要通过 ALAssetsLibrary 来访问它们:

var url = e.Info[UIImagePickerController.ReferenceUrl] as NSUrl;
var asset = new ALAssetsLibrary();
UIImage image;
asset.AssetForUrl(
    url, 
    (ALAsset obj) =>
    {
        var assetRep = obj.DefaultRepresentation;
        var cGImage = assetRep.GetFullScreenImage();
        image = new UIImage(cGImage);
        // Do something with "image" here... i.e.: assign it to a UIImageView
        imageView.Image = image;
    }, 
    (NSError err) => 
    { 
        Console.WriteLine(err);
    }
);

注意:如果您不必支持 iOS 7 客户端，您真的应该开始使用 Photos 框架....

The Assets Library framework is deprecated as of iOS 9.0. Instead, use the Photos framework instead, which in iOS 8.0 and later provides more features and better performance for working with a user’s photo library.

引用:https://developer.apple.com/library/ios/documentation/AssetsLibrary/Reference/ALAssetsLibrary_Class/index.html