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

Xcode 12•Swift 5

Leo Dabus的答案非常棒!我只是想提供一个一体化的功能解决方案:

if let url = URL(string: "http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") {
    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data, error == nil else { return }
        
        DispatchQueue.main.async { /// execute on main thread
            self.imageView.image = UIImage(data: data)
        }
    }
    
    task.resume()
}

其他回答

斯威夫特 2.2 ||Xcode 7.3

我得到了惊人的成绩!!使用AlamofireImage swift库

它提供了多种功能,如:

异步下载 自动清除图像缓存,如果内存警告发生的应用程序 图像URL缓存 图像缓存 避免重复下载

在你的应用中很容易实现

步骤1安装吊舱


Alamofire 3 x 3。

宾夕法尼亚州’Alamofire’

AlamofireImage 2。4 . x

宾夕法尼亚州’AlamofireImage’

步骤2导入并使用

import Alamofire
import AlamofireImage

let downloadURL = NSURL(string: "http://cdn.sstatic.net/Sites/stackoverflow/company/Img/photos/big/6.jpg?v=f4b7c5fee820")!
imageView.af_setImageWithURL(downloadURL)

就是这样! !它会照顾好一切


非常感谢Alamofire的伙计们,让iDevelopers的生活变得简单了;)

Xcode 12•Swift 5

Leo Dabus的答案非常棒!我只是想提供一个一体化的功能解决方案:

if let url = URL(string: "http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") {
    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data, error == nil else { return }
        
        DispatchQueue.main.async { /// execute on main thread
            self.imageView.image = UIImage(data: data)
        }
    }
    
    task.resume()
}

这是从URL加载/下载图像的工作代码。NSCache自动和显示占位符图像下载和加载实际图像(Swift 4 | Swift 5代码)。

func NKPlaceholderImage(image:UIImage?, imageView:UIImageView?,imgUrl:String,compate:@escaping (UIImage?) -> Void){
    
    if image != nil && imageView != nil {
        imageView!.image = image!
    }
    
    var urlcatch = imgUrl.replacingOccurrences(of: "/", with: "#")
    let documentpath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
    urlcatch = documentpath + "/" + "\(urlcatch)"
    
    let image = UIImage(contentsOfFile:urlcatch)
    if image != nil && imageView != nil
    {
        imageView!.image = image!
        compate(image)
        
    }else{
        
        if let url = URL(string: imgUrl){
            
            DispatchQueue.global(qos: .background).async {
                () -> Void in
                let imgdata = NSData(contentsOf: url)
                DispatchQueue.main.async {
                    () -> Void in
                    imgdata?.write(toFile: urlcatch, atomically: true)
                    let image = UIImage(contentsOfFile:urlcatch)
                    compate(image)
                    if image != nil  {
                        if imageView != nil  {
                            imageView!.image = image!
                        }
                    }
                }
            }
        }
    }
}

像这样使用:

// Here imgPicture = your imageView
// UIImage(named: "placeholder") is Display image brfore download and load actual image. 

NKPlaceholderImage(image: UIImage(named: "placeholder"), imageView: imgPicture, imgUrl: "Put Here your server image Url Sting") { (image) in }

编辑为最新更改2021年9月

// It's better to use extension 
extension UIImageView {
func downloadImage(from URLString: String, with completion: @escaping (_ response: (status: Bool, image: UIImage? ) ) -> Void) {
    guard let url = URL(string: URLString) else {
        completion((status: false, image: nil))
        return
    }
    
    URLSession.shared.dataTask(with: url) { data, response, error in
        guard error == nil else {
            completion((status: false, image: nil))
            return
        }
        
        guard let httpURLResponse = response as? HTTPURLResponse,
              httpURLResponse.statusCode == 200,
              let data = data else {
            completion((status: false, image: nil))
            return
        }
        
        let image = UIImage(data: data)
        completion((status: true, image: image))
    }.resume()
}
}

快乐的鳕鱼。欢呼:)

斯威夫特4

这个方法将从一个网站异步下载图像并缓存它:

    func getImageFromWeb(_ urlString: String, closure: @escaping (UIImage?) -> ()) {
        guard let url = URL(string: urlString) else {
return closure(nil)
        }
        let task = URLSession(configuration: .default).dataTask(with: url) { (data, response, error) in
            guard error == nil else {
                print("error: \(String(describing: error))")
                return closure(nil)
            }
            guard response != nil else {
                print("no response")
                return closure(nil)
            }
            guard data != nil else {
                print("no data")
                return closure(nil)
            }
            DispatchQueue.main.async {
                closure(UIImage(data: data!))
            }
        }; task.resume()
    }

在使用:

    getImageFromWeb("http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") { (image) in
        if let image = image {
            let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
            imageView.image = image
            self.view.addSubview(imageView)
        } // if you use an Else statement, it will be in background
    }