créer un chargement d'image/indicateur d'activité, jusqu'à ce que l'image est affichée à l'écran dans swift

Question

je veux afficher un indicateur d'activité à l'écran pendant que l'image est téléchargée à partir d'un site Web puis montrer dans les images.image c'est mon code ci-dessous. chaque fois que je télécharge l'image, j'imprime le statut tout de suite et l'indicateur d'activité n'apparaît jamais. été à la recherche à travers le web, mais je ne comprenais toujours pas. s'il vous plaît aider

let mygroup = DispatchGroup() 
var activityIndicator = UIActivityIndicatorView() 

func downloadpic(sender:UIButton){ 
    let catPictureURL = URL(string: addr)! 

    // Creating a session object with the default configuration. 
    // You can read more about it here https://developer.apple.com/reference/foundation/urlsessionconfiguration 
    let session = URLSession(configuration: .default) 

    // Define a download task. The download task will download the contents of the URL as a Data object and then you can do what you wish with that data. 

    let downloadPicTask = session.dataTask(with: catPictureURL) { (data, response, error) in 
     // The download has finished. 
     if let e = error { 
      print("Error downloading cat picture: \(e)") 
     } else { 
      // No errors found. 
      // It would be weird if we didn't have a response, so check for that too. 
      if let res = response as? HTTPURLResponse { 
       // put loading screen here 
       self.activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .white) 
       self.activityIndicator.frame = CGRect(x: 0, y: 0, width: 46, height: 46) 
       self.activityIndicator.startAnimating() 
       self.mygroup.enter() 
       print("downloading image") 
       print("Downloaded cat picture with response code \(res.statusCode)") 
       if let imageData = data { 
        // Finally convert that Data into an image and do what you wish with it. 
        self.images.image = UIImage(data: imageData) 
         self.mygroup.leave() 
         print("image already downloaded") 
         self.activityIndicator.stopAnimating() 
         self.activityIndicator.hidesWhenStopped = true 


        // Do something with your image. 
       } else { 
        print("Couldn't get image: Image is nil") 
       } 
      } else { 
       print("Couldn't get response code for some reason") 
      } 
     } 
    } 

    downloadPicTask.resume() 
} 

Answer 1

Vous avez obtenu ce problème, parce que:

1. Vous n'avez pas ajouté le activityIndicator à des vues
2. Vous avez configuré le activityIndicator dans le completionHandler bloc

Let configurer dans le activityIndicator la méthode viewDidLoad():

self.activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray) 
self.activityIndicator.frame = CGRect(x: 0, y: 0, width: 46, height: 46) 
self.activityIndicator.hidesWhenStopped = true 

view.addSubview(self.activityIndicator) 

Et commencer à animer avant de reprendre la dataTask

self.activityIndicator.startAnimating() 

Ensuite, arrêtez-vous dans le completionHandler

self.activityIndicator.stopAnimating() 

Le code final:

let mygroup = DispatchGroup() 
var activityIndicator = UIActivityIndicatorView() 

override func viewDidLoad() { 
    super.viewDidLoad() 

    self.activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray) 
    self.activityIndicator.frame = CGRect(x: 0, y: 0, width: 46, height: 46) 
    self.activityIndicator.hidesWhenStopped = true 

    view.addSubview(self.activityIndicator) 
} 

func downloadpic(sender: UIButton) { 
    let catPictureURL = URL(string: addr)! 

    // Creating a session object with the default configuration. 
    // You can read more about it here https://developer.apple.com/reference/foundation/urlsessionconfiguration 
    let session = URLSession(configuration: .default) 

    // Define a download task. The download task will download the contents of the URL as a Data object and then you can do what you wish with that data. 

    self.activityIndicator.startAnimating() 

    let downloadPicTask = session.dataTask(with: catPictureURL) { (data, response, error) in 
     // The download has finished. 
     if let e = error { 
      print("Error downloading cat picture: \(e)") 
     } else { 
      // No errors found. 
      // It would be weird if we didn't have a response, so check for that too. 
      if let res = response as? HTTPURLResponse { 
       // put loading screen here 

       self.mygroup.enter() 
       print("downloading image") 
       print("Downloaded cat picture with response code \(res.statusCode)") 
       if let imageData = data { 
        // Finally convert that Data into an image and do what you wish with it. 
        self.images.image = UIImage(data: imageData) 
        self.mygroup.leave() 
        print("image already downloaded") 
        self.activityIndicator.stopAnimating() 

        // Do something with your image. 
       } else { 
        print("Couldn't get image: Image is nil") 
       } 
      } else { 
       print("Couldn't get response code for some reason") 
      } 
     } 
    } 

    downloadPicTask.resume() 
} 

Le résultat!