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

我把这个问题的最佳答案的代码包装成一个单一的,可重用的类扩展UIImageView,所以你可以直接在你的故事板中使用异步加载UIImageViews(或从代码中创建它们)。

这是我的班级:

import Foundation
import UIKit

class UIImageViewAsync :UIImageView
{

    override init()
    {
        super.init(frame: CGRect())
    }

    override init(frame:CGRect)
    {
        super.init(frame:frame)
    }

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    func getDataFromUrl(url:String, completion: ((data: NSData?) -> Void)) {
        NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: url)!) { (data, response, error) in
            completion(data: NSData(data: data))
        }.resume()
    }

    func downloadImage(url:String){
        getDataFromUrl(url) { data in
            dispatch_async(dispatch_get_main_queue()) {
                self.contentMode = UIViewContentMode.ScaleAspectFill
                self.image = UIImage(data: data!)
            }
        }
    }
}

下面是如何使用它:

imageView.downloadImage("http://www.image-server.com/myImage.jpg")

其他回答

唯一缺少的是一件东西!

let url = NSURL.URLWithString("http://live-wallpaper.net/iphone/img/app/i/p/iphone-4s-wallpapers-mobile-backgrounds-dark_2466f886de3472ef1fa968033f1da3e1_raw_1087fae1932cec8837695934b7eb1250_raw.jpg");
var err: NSError?
var imageData :NSData = NSData.dataWithContentsOfURL(url!,options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
var bgImage = UIImage(data:imageData!)

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!)
            }
        }
    }
}

一个快速的黑客,如果你想快速检查图像从url

 let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
 let imagedData = NSData(contentsOfURL: imageURL!)!
 imageView?.image = UIImage(data: imagedData)

我在一个tableview中实现了一个只有图像的自定义单元格

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{
        
        let cell = tableView.dequeueReusableCellWithIdentifier("theCell", forIndexPath: indexPath) as! customTableViewCell

        let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
        
        let imagedData = NSData(contentsOfURL: imageURL!)!
            
        cell.imageView?.image = UIImage(data: imagedData)
        
        return cell
        
    }

干净的方式:

extension URL {
    var favIcon16: UIImage? { getFav(ofSize: .s) }
    var favIcon32: UIImage? { getFav(ofSize: .m) }
    var favIcon64: UIImage? { getFav(ofSize: .l) }
    var favIcon128: UIImage? { getFav(ofSize: .xl) }
    var favIcon256: UIImage? { getFav(ofSize: .xxl) }
    var favIcon512: UIImage? { getFav(ofSize: .xxxl) }

    private func getFav(ofSize s: FavSize) -> UIImage? {
        guard UIApplication.shared.canOpenURL(self),
              let favUrl = URL(string: "https://www.google.com/s2/favicons?sz=\(s.rawValue)&domain=\(self.absoluteURL)"),
              let data = try? Data(contentsOf: favUrl)
        else { return nil }
        return UIImage(data: data)
 }
    private enum FavSize: Int, CaseIterable { case s = 16, m = 32, l = 64, xl = 128, xxl = 256, xxxl = 512 }
}

和用法:

let myUrl = URL(string: "http://facebook.com")
myImgView.image = myUrl.favIcon16

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。