IOS 多线程、进程

///使用线程下载图片
 1 var imageView = UIImageView()
 2 var label = UILabel()
 接着对viewDidLoad方法进行修改，对imageView属性和label属性进
 行初始化，并创建一个新的线程来执行网络图片的下载工作。
 3 override func viewDidLoad() {
 4 super.viewDidLoad()
 5 // Do any additional setup after loading the view,
 typically from a nib.
 6 imageView = UIImageView(frame：CGRect(x：0, y：
 260, width：320, height：300))
 7 self.view.addSubview(imageView)
 8
 9 label = UILabel(frame：CGRect(x：0, y：0, width：
 320, height：568))
 10 label.backgroundColor = UIColor.white
 11 label.textAlignment = .center
 12 label.text = “Loading……”
 13 label.font = UIFont.systemFont(ofSize：42)
 14 self.view.addSubview(label)
 15
 16 let imageUrl =
 “http：//images.apple.com/v/iphone/home/s/home/images/trade_in_iphone_17 let thread = Thread(target：self, selector：
 selector(ViewController.downloadImage), object： imageUrl)
 18 thread.start()
 19 }
 20 func downloadImage(path：String){
 21 let url = URL(string：path)
 22 var data：Data！
 23 do{
 24 try data = Data(contentsOf：url！)
 25 let image = UIImage(data：data)
 26 self.perform(#selector(ViewController.showImage),
 on：Thread.main, with：image, waitUntilDone：true)
 27 }catch{
 28 print(“下载图片失败。”)
 29 }
 30 }
 31 func showImage(image：UIImage){
 32 self.imageView.image = image
 33 self.label.isHidden = true
 34 }