iOS WidgetKit: remote images fails to load

Question

I'm observing a bizarre thing: in the new widgets far too often remote images are not being displayed even though the image has been successfully loaded and placed in cache.

For image downloading I've tried:

• SDWebImageSwiftUI
• Kingfisher
• SwURL

All of them indicate that image loading succeed, but the actual widget is not showing it.

struct TestWidgetEntryView : View {
    var entry: Provider.Entry

    var body: some View {
        WebImage(url: URL(string: "https://miro.medium.com/max/3840/0*TLqp5Uwavd-U_xrs.jpg"))
                        .onSuccess()
                        .resizable()
    }
}

On the second run of the debugger - with image loading from cache - I get the image displayed, but never(?) on initial run.

It feels like that in onSuccess I need to trigger UI-invalidation? But how?

(Since it happens to literally every image-lib I try - I don't think that it's something off in the libs)

Environment:

• iOS 14 Beta 3 (both device and simulators)
• Xcode 12 Beta 3
• During the debug run, memory use is around 15mb

Answer 1

Yes, as mentioned by Konstantin, it is not supported to load images asynchronously. There are 2 options to load network image in widgets

1. Either fetch all the images in TimelineProvider and inject them to the views directly.

   OR

2. Use Data(contentsOf: url) to fetch the image. This way it still fetches them synchronously but the code is cleaner. Sample code -

   struct NetworkImage: View {
   
     private let url: URL?
   
     var body: some View {
   
       Group {
        if let url = url, let imageData = try? Data(contentsOf: url), 
          let uiImage = UIImage(data: imageData) {
   
          Image(uiImage: uiImage)
            .resizable()
            .aspectRatio(contentMode: .fill)
         } 
         else {
          Image("placeholder-image")
         }
       }
     }
   
   }
   

This view can simply be use like this -

NetworkImage(url: url)

Answer 2

Got it: it's simply not supported and you aim to load images inside TimelineProvider:

https://developer.apple.com/forums/thread/652581