在Swift上从URL加载/下载图像

我想从我的应用程序中的URL加载图像，所以我首先尝试了Objective-C和它的工作，但是，与Swift，我有一个编译错误:

'imageWithData'不可用:使用对象构造'UIImage(data:)'

我的函数:

@IBOutlet var imageView : UIImageView

override func viewDidLoad() {
    super.viewDidLoad()

    var url:NSURL = NSURL.URLWithString("http://myURL/ios8.png")
    var data:NSData = NSData.dataWithContentsOfURL(url, options: nil, error: nil)

    imageView.image = UIImage.imageWithData(data)// Error here
}

在objective - c中:

- (void)viewDidLoad {
    [super viewDidLoad];

    NSURL *url = [NSURL URLWithString:(@"http://myURL/ios8.png")];
    NSData *data = [NSData dataWithContentsOfURL:url];

    _imageView.image = [UIImage imageWithData: data];
    _labelURL.text = @"http://www.quentinroussat.fr/assets/img/iOS%20icon's%20Style/ios8.png";
 }

有人能解释一下为什么imageWithData:不能与Swift一起工作，我该如何解决这个问题。

当前回答

供你参考:对于swift-2.0 Xcode7.0 beta2

extension UIImageView {
    public func imageFromUrl(urlString: String) {
        if let url = NSURL(string: urlString) {
            let request = NSURLRequest(URL: url)
            NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) {
            (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in
                self.image = UIImage(data: data!)
            }
        }
    }
}

2015-07-13 06:05:55

其他回答

Swift 4.1我创建了一个函数，只是传递图像url，图像生成后缓存键设置为完成块。

   class NetworkManager: NSObject {
  
  private var imageQueue = OperationQueue()
  private var imageCache = NSCache<AnyObject, AnyObject>()
  
  func downloadImageWithUrl(imageUrl: String, cacheKey: String, completionBlock: @escaping (_ image: UIImage?)-> Void) {
    
    let downloadedImage = imageCache.object(forKey: cacheKey as AnyObject)
    if let  _ = downloadedImage as? UIImage {
      completionBlock(downloadedImage as? UIImage)
    } else {
      let blockOperation = BlockOperation()
      blockOperation.addExecutionBlock({
        let url = URL(string: imageUrl)
        do {
          let data = try Data(contentsOf: url!)
          let newImage = UIImage(data: data)
          if newImage != nil {
            self.imageCache.setObject(newImage!, forKey: cacheKey as AnyObject)
            self.runOnMainThread {
              completionBlock(newImage)
            }
          } else {
            completionBlock(nil)
          }
        } catch {
          completionBlock(nil)
        }
      })
      self.imageQueue.addOperation(blockOperation)
      blockOperation.completionBlock = {
        print("Image downloaded \(cacheKey)")
      }
    }
  }
}
extension NetworkManager {
  fileprivate func runOnMainThread(block:@escaping ()->Void) {
    if Thread.isMainThread {
      block()
    } else {
      let mainQueue = OperationQueue.main
      mainQueue.addOperation({
        block()
      })
    }
  }
}

2018-08-19 14:53:53

您可以使用pod SDWebImage来实现相同的功能。它很容易使用。你可以在SDWebImage这里获得文档

下面是示例代码

self.yourImage.sd_setImage(with: NSURL(string: StrUrl as String ) as URL!, placeholderImage: placeholderImage, options: SDWebImageOptions(rawValue: 0), completed: { (image, error, cacheType, imageURL) in
                if( error != nil)
                {
                    print("Error while displaying image" , (error?.localizedDescription)! as String)
                }
            })

2018-10-10 10:21:42

在Swift中使用此代码

imageView.image=UIImage(data: NSData(contentsOfURL: NSURL(string: "http://myURL/ios8.png")!)!

2016-04-19 10:56:58

供你参考:对于swift-2.0 Xcode7.0 beta2

extension UIImageView {
    public func imageFromUrl(urlString: String) {
        if let url = NSURL(string: urlString) {
            let request = NSURLRequest(URL: url)
            NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) {
            (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in
                self.image = UIImage(data: data!)
            }
        }
    }
}

2015-07-13 06:05:55

斯威夫特4::

这将在加载图像时显示加载器。你可以使用NSCache临时存储图像

let imageCache = NSCache<NSString, UIImage>()
extension UIImageView {
    func loadImageUsingCache(withUrl urlString : String) {
        let url = URL(string: urlString)
        if url == nil {return}
        self.image = nil

        // check cached image
        if let cachedImage = imageCache.object(forKey: urlString as NSString)  {
            self.image = cachedImage
            return
        }

        let activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView.init(activityIndicatorStyle: .gray)
        addSubview(activityIndicator)
        activityIndicator.startAnimating()
        activityIndicator.center = self.center

        // if not, download image from url
        URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
            if error != nil {
                print(error!)
                return
            }

            DispatchQueue.main.async {
                if let image = UIImage(data: data!) {
                    imageCache.setObject(image, forKey: urlString as NSString)
                    self.image = image
                    activityIndicator.removeFromSuperview()
                }
            }

        }).resume()
    }
}

用法:-

truckImageView.loadImageUsingCache(withUrl: currentTruck.logoString)

2018-09-14 10:40:17

在Swift上从URL加载/下载图像

推荐文章

最新文章

标签