ios - 从 URL 下载图片 iOS 10 Swift 3

Question

这个问题已经有答案了:

session.dataTaskWithURL completionHandler never called (1 个回答)

已关闭 6 年前。

这是我之前使用的从 url 下载图像的函数。我使用的是 swift 2.3 版本。

let request: NSMutableURLRequest = NSMutableURLRequest(URL: url)
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: {(response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in
  if (error == nil) {
    let image: UIImage = UIImage(data: data!)!
    completionBlock(succeeded: true, image: image)
  }
  else {
    completionBlock(succeeded: false, image: UIImage(named: "user_icon")!)
  }
})

现在我已将代码转换为Swift 3，新代码如下。下面的代码没有调用完成处理程序。谁能帮我这个？这是 swift 3 代码。

let sessionTask = URLSession.shared
let request = URLRequest(url: url)
sessionTask.dataTask(with: request, completionHandler: {(data: Data?, response: URLResponse?, error: Error?) -> Void in
  if (error == nil) {
    let image: UIImage = UIImage(data: data!)!
    completionBlock(true, image)
  }
  else {
    completionBlock(false, UIImage(named: "user_icon")!)
  }
})

Answer 1

您尚未开始任务。

将您的任务存储在变量中...

let task = session.dataTask(...

...然后开始任务:

task.resume() //yes, it's always called "resume". Even if the task wasn't started yet