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

这是最简单的方法，你不必担心async，或者它是如何工作的。

import SDWebImage

imageView.sd_setImage(with: URL(string: ".net/path/to/image.jpg"), placeholderImage: UIImage(named: "placeholder.png"))
Using UIImageView+WebCache category with UI

这里有一篇关于它的详细博文。

2021-12-15 21:39:32

其他回答

你可以很容易地下载图像从图像url翠鸟。

首先进口翠鸟as-

pod 'Kingfisher'

然后在类中以-的形式导入它

import Kingfisher

之后添加一个临时的UIImageView

let imgView = UIImageView()
imgView.kf.setImage(with: yourImageURL)

if let finalImage = imgView.image {
    // finalImage is your image
}

2021-10-13 04:58:38

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()
}

2016-09-23 17:18:49

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

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

斯威夫特2。x答案下载图像到文件(与Leo Dabus的答案相反，它将图像存储在内存中)。根据Leo Dabus的回答和Rob的回答，从完成处理程序的NSURLSession DownloadTaskWithRequest中获取数据:

    // Set download vars
    let downloadURL = NSURL() // URL to download from
    let localFilename = "foobar.png" // Filename for storing locally 

    // Create download request
    let task = NSURLSession.sharedSession().downloadTaskWithURL(downloadURL) { location, response, error in
        guard location != nil && error == nil else {
            print("Error downloading message: \(error)")
            return
        }

        // If here, no errors so save message to permanent location
        let fileManager = NSFileManager.defaultManager()
        do {
            let documents = try fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
            let fileURL = documents.URLByAppendingPathComponent(localFilename)
            try fileManager.moveItemAtURL(location!, toURL: fileURL)
            self.doFileDownloaded(fileURL, localFilename: localFilename)
            print("Downloaded message @ \(localFilename)")
        } catch {
            print("Error downloading message: \(error)")
        }
    }

    // Start download
    print("Starting download @ \(downloadURL)")
    task.resume()


// Helper function called after file successfully downloaded
private func doFileDownloaded(fileURL: NSURL, localFilename: String) {

    // Do stuff with downloaded image

}

2016-04-21 19:57:24

在Swift上从URL加载/下载图像

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