来自 URL 的快速图像未显示

Question

我是 swift 的新手，不确定为什么从 url 加载图像。代码：

        let url = NSURL(string: imageURL)
    let task = NSURLSession.sharedSession().dataTaskWithURL(url!, completionHandler: { (data, response, error) -> Void in
        println("Should load the pic!")
        var profilePic = UIImage(data: data)
        self.profileImage.setImage(profilePic)
    })

在我的接口控制器中，我有一个名为"profileImage"的图像，它与IBOutlet链接。我注意到的一件事是"应该加载图片！"没有出现在控制台中，所以它没有进入setImage代码。

Answer 1

当您从URL下载图像时。我建议你在后台这样做。下面是适合您的示例代码：

import UIKit
class ViewController: UIViewController {
@IBOutlet weak var profileImage: UIImageView!
override func viewDidLoad() {
    super.viewDidLoad()
    profileImage.contentMode = UIViewContentMode.ScaleAspectFit
    if let checkedUrl = NSURL(string: "http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") {
        downloadImage(checkedUrl)
    }
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func getDataFromUrl(urL:NSURL, completion: ((data: NSData?) -> Void)) {
    NSURLSession.sharedSession().dataTaskWithURL(urL) { (data, response, error) in
        completion(data: NSData(data: data))
        }.resume()
}
func downloadImage(url:NSURL){
    println("Started downloading "(url.lastPathComponent!.stringByDeletingPathExtension)".")
    getDataFromUrl(url) { data in
        dispatch_async(dispatch_get_main_queue()) {
            println("Finished downloading "(url.lastPathComponent!.stringByDeletingPathExtension)".")
            self.profileImage.image = UIImage(data: data!)
        }
    }
}
}

Answer 2

试试这个，因为它可能会帮助你：

dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
    var profilePic =  UIImage(data: NSData(contentsOfURL: NSURL(string:"http://devhumor.com/wp-content/uploads/2012/04/devhumor.com_pointers.png")));
    self.profileImage.setImage(profilePic);
});