从 WatchKit 上的 URL 加载图像

Question

在手表上加载外部图像是否有比以下更优雅的解决方案？

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)
    }
}

Answer 1

NSURL 用于本地文件。而是使用 NSURLSession。设置远程图像的比例也很有用。

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
    }
}

这样使用

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

Answer 2

这是分类

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
    }

}

这样使用

 self.imageView.setImageWithUrl(image_url)

Answer 3

我认为该解决方案很好，因为它可以帮助您的应用程序在您尝试从网络加载一些图像时摆脱滞后。 你可以像这样创建一个新函数：

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)
        }
    }

}

之后你想从 urlString 加载图像的任何地方都可以这样使用：

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

希望对您有所帮助。

Answer 4

我认为通过这个解决方案，您可以将图像存储在缓存中并从缓存中显示图像。所以您可以调用此函数并使用它。

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)
                }
            }
        }
    }
}

Answer 5

刚做了同样的任务，这里的答案对我有帮助，但我需要做一些修改。所以我想在这里分享常见答案的更新版本（没有任何强制解包）（应该与 Swift 4.2 一起使用）：

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)")
        }
    }
}

}

Answer 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
    }
}

Answer 7

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

             imageWK.setImage(UIImage(data: data))

        }
    }

试试这个代码。 不要忘记在您的 Plist 中添加 NSTransportSecurity。

Answer 8

斯威夫特 4.2

使用 URLSession、正确的 GCD 和 @discardableResult 来消除 Result of call to '...' is unused 警告。

plist
App Transport Security Settings
Allow Arbitrary Loads - YES

如果您愿意，您可以在故事板中设置 100x100 的固定图像尺寸。

let url = "https://i.imgur.com/UZbLC0Q.jpg"

public extension WKInterfaceImage {

    @discardableResult 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
    }
}

打电话

row.image.setImageWithUrl(url: url, scale: 1.0)