Load image from URL on WatchKit

问题:

Is there a more elegant solution to load an external image on the watch than the following ?

let image_url:String = "http://placehold.it/350x150"

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
    let url:NSURL = NSURL(string:image_url)!
    var data:NSData = NSData(contentsOfURL: url)!
    var placeholder = UIImage(data: data)!

    // update ui
    dispatch_async(dispatch_get_main_queue()) {
        self.imageView.setImage(placeholder)
    }
}

回答1:

NSURL is meant to be used for local files. Instead use NSURLSession. It's also useful to set the scale for the remote image.

import WatchKit

public extension WKInterfaceImage {

    public func setImageWithUrl(url:String, scale: CGFloat = 1.0) -> WKInterfaceImage? {

        NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: url)!) { data, response, error in
            if (data != nil && error == nil) {
                let image = UIImage(data: data!, scale: scale)

                dispatch_async(dispatch_get_main_queue()) {
                    self.setImage(image)
                }
            }
        }.resume()

        return self
    }
}

Use it like this

self.imageView.setImageWithUrl(image_url, scale: 2.0)

回答2:

Here is the category

import WatchKit

public extension WKInterfaceImage {

    public func setImageWithUrl(url:String) -> WKInterfaceImage? {

        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
            let url:NSURL = NSURL(string:url)!
            var data:NSData = NSData(contentsOfURL: url)!
            var placeholder = UIImage(data: data)!

            dispatch_async(dispatch_get_main_queue()) {
                self.setImage(placeholder)
            }
        }

        return self
    }

}

Use it like this

 self.imageView.setImageWithUrl(image_url)

回答3:

I thinks that solution is good because it can help your application out of lagging when you're trying to load some Images from web. you can make a new function like this:

func loadImage(url:String, forImageView: WKInterfaceImage) {
// load image
    let image_url:String = url
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
        let url:NSURL = NSURL(string:image_url)!
        var data:NSData = NSData(contentsOfURL: url)!
        var placeholder = UIImage(data: data)!

// update ui
        dispatch_async(dispatch_get_main_queue()) {
            forImageView.setImage(placeholder)
        }
    }

}

after that any where you want to load image from urlString you can use like this:

loadImage("http://...", forImageView: self.myImageView)

Hope this help.

回答4:

I think by this solution you can store image in cache and display image from cache also.so you can call this function and use it.

func loadImage(url:String, forImageView: WKInterfaceImage) {

    forImageView.setImageNamed("placeholder")
    let image_url:String = url

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {

        let url:NSURL = NSURL(string:image_url)!
        print(url)

        //if image is already stored in cache
        if WKInterfaceDevice.currentDevice().cachedImages[image_url] != nil{
            dispatch_async(dispatch_get_main_queue()) {
                forImageView.setImageNamed(image_url)
            }
        }else{
            if let data = NSData(contentsOfURL: url){

                //load image
                let image = UIImage(data: data)!
                //Store image in cache
                WKInterfaceDevice.currentDevice().addCachedImage(image, name: image_url)
                dispatch_async(dispatch_get_main_queue()) {
                    forImageView.setImage(placeholder)
                }
            }
        }
    }
}

回答5:

     if let url = NSURL(string: "http://google.net/img/upload/photo2.png") {
            if let data = NSData(contentsOfURL: url){

             imageWK.setImage(UIImage(data: data))

        }
    }

Try this code. Dont forget to add NSTransportSecurity in your Plist.

回答6:

public extension WKInterfaceImage {

    public func setImageWithUrl(url:String, scale: CGFloat = 1.0) -> WKInterfaceImage? {

        URLSession.shared.dataTask(with: NSURL(string: url)! as URL) { data, response, error in
            if (data != nil && error == nil) {
                let image = UIImage(data: data!, scale: scale)

                DispatchQueue.main.async() {
                   self.setImage(image)
                }
        }
        }.resume()

    return self
}

}

回答7:

Just had the same task, the answers here helped me, but I needed to do some modifications. So I wanted to share the updated version (without any forced unwraps) of the common answers here (should work with Swift 4.2):

public extension WKInterfaceImage {

public func setBackgroundImage(url: String) {
    let asyncQueue = DispatchQueue(label: "backgroundImage")
    asyncQueue.async {
        do {
            if let url = URL(string: url) {
                let data = try Data(contentsOf: url)
                if let placeholder = UIImage(data: data) {
                    self.setImage(placeholder)
                }
            }
        } catch let error {
            print("Could not set backgroundImage for WKInterfaceImage: \(error.localizedDescription)")
        }
    }
}

}