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

斯威夫特5

extension UIImageView {
    func load(url: URL) {
        DispatchQueue.global().async { [weak self] in
            if let data = try? Data(contentsOf: url) {
                if let image = UIImage(data: data) {
                    DispatchQueue.main.async {
                        self?.image = image
                    }
                }
            }
        }
    }
}

使用

override func awakeFromNib() {
    super.awakeFromNib()
   if let url = URL(string:"<imageURLHere>"){
     imgView.load(url: url)
   }
}

其他回答

斯威夫特5

extension UIImageView {
    func load(url: URL) {
        DispatchQueue.global().async { [weak self] in
            if let data = try? Data(contentsOf: url) {
                if let image = UIImage(data: data) {
                    DispatchQueue.main.async {
                        self?.image = image
                    }
                }
            }
        }
    }
}

使用

override func awakeFromNib() {
    super.awakeFromNib()
   if let url = URL(string:"<imageURLHere>"){
     imgView.load(url: url)
   }
}

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 }

Swift 2带有错误句柄和自定义请求头

简单地添加扩展到UIImageView:

extension UIImageView {
    public func imageFromUrl(urlString: String) {
        if let url = NSURL(string: urlString) {
            let request = NSMutableURLRequest(URL: url)
            request.setValue("<YOUR_HEADER_VALUE>", forHTTPHeaderField: "<YOUR_HEADER_KEY>")
            NSURLSession.sharedSession().dataTaskWithRequest(request) {
                (data, response, error) in
                guard let data = data where error == nil else{
                    NSLog("Image download error: \(error)")
                    return
                }

                if let httpResponse = response as? NSHTTPURLResponse{
                    if httpResponse.statusCode > 400 {
                        let errorMsg = NSString(data: data, encoding: NSUTF8StringEncoding)
                        NSLog("Image download error, statusCode: \(httpResponse.statusCode), error: \(errorMsg!)")
                        return
                    }
                }

            dispatch_async(dispatch_get_main_queue(), {
                NSLog("Image download success")
                self.image = UIImage(data: data)
            })
            }.resume()
        }
    }
}

然后,使用新的imageFromUrl(urlString: String)下载图像

用法:

imageView.imageFromUrl("https://i.imgur.com/ONaprQV.png")
class ImageStore: NSObject { 
    static let imageCache = NSCache<NSString, UIImage>()
}

extension UIImageView {
    func url(_ url: String?) {
        DispatchQueue.global().async { [weak self] in
            guard let stringURL = url, let url = URL(string: stringURL) else {
                return
            }
            func setImage(image:UIImage?) {
                DispatchQueue.main.async {
                    self?.image = image
                }
            }
            let urlToString = url.absoluteString as NSString
            if let cachedImage = ImageStore.imageCache.object(forKey: urlToString) {
                setImage(image: cachedImage)
            } else if let data = try? Data(contentsOf: url), let image = UIImage(data: data) {
                DispatchQueue.main.async {
                    ImageStore.imageCache.setObject(image, forKey: urlToString)
                    setImage(image: image)
                }
            }else {
                setImage(image: nil)
            }
        }
    }
}

用法:

let imageView = UIImageView()
imageView.url("image url")

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;)