ios - 来自 URL 的 Swift 图片未显示

Question

我是 swift 的新手，不确定为什么要从 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)
    })

在我的界面 Controller 中，我有一个名为“profileImage”的图像，它与一个 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，所以它没有到达 setImage 代码..

Answer 1

当您从 URL 下载图像时。我建议你在后台执行此操作。这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!)
        }
    }
}
}