How to download images async for WidgetKit

user_1396701 0
Viewed 4176

I am developing Widgets for iOS and I really don't know how to download images for the widgets.

The widget currently downloads an array of Objects, and every object has a URL of an image. The idea is that every object makes a SimpleEntry for the Timeline.

What's the best way of achieving this? I read that Widgets shouldn't use the ObservableObject. I fetch the set of objects in the timeline provider, which seems to be what Apple recommends. But do I also download the images there and I wait until all are done to send the timeline?

Any advice would be very helpful,

urlsession widgetkit swiftui ios
2 Answers

Yes, you should download the images in the timeline provider and send the timeline when they are all done. Refer to the following recommendation by an Apple frameworks engineer.

I use a dispatch group to achieve this. Something like:

let imageRequestGroup = DispatchGroup()
var images: [UIImage] = []
for imageUrl in imageUrls {
    imageRequestGroup.enter()
    yourAsyncUIImageProvider.getImage(fromUrl: imageUrl) { image in
        images.append(image)
        imageRequestGroup.leave()
    }
}
imageRequestGroup.notify(queue: .main) {
    completion(images)
}

I then use SwiftUI's Image(uiImage:) initializer to display the images

user_14078890

I dont have a good solution, but I try to use WidgetCenter.shared.reloadAllTimelines(), and it make sence. In the following code.

var downloadImage: UIImage?

func downloadImage(url: URL) -> UIImage {
    
    var picImage: UIImage!
    
    if self.downloadImage == nil {
        
        picImage = UIImage(named: "Default Image")
        
        DispatchQueue.global(qos: .background).async {
            do {
                let data = try Data(contentsOf: url)
                DispatchQueue.main.async {
                    self.downloadImage = UIImage.init(data: data)
                    if self.downloadImage != nil {
                        DispatchQueue.main.async {
                            WidgetCenter.shared.reloadAllTimelines()
                        }
                    }
                }
            } catch { }
        }
    } else {
        picImage = self.downloadImage
    }
    
    return picImage
}

Also you have to consider when to delete this picture. This like tableView.reloadData().

user_142361110
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