Start animating UIActivityIndicator when image downloads throug contentsOfURL synchronous

Question

I am trying to show UIActivityIndicator when images start downloading, and it animate until all images are downloads. But UIActivityIndicator not animate, it animate when all images are downloads. I've found that contentsOfURL is synchronous method and blocks the main thread. I want to use contentsOfURL for downloading images. Anyone have any idea how i can animate UIActivityIndicator when images start downloading? Thanks

var indeX = 0  
var imageArrayNsData : [NSData] = []
var posts = NSMutableArray()

myActivityIndicator.startAnimating()
self.view.addSubview(myActivityIndicator)
self.view.userInteractionEnabled = false

for _ in posts.valueForKey("enclosure") as! [NSString]{
    let picURL = self.posts.objectAtIndex(indeX).valueForKey("enclosure") as! String
    let url = NSURL(string: picURL)
    let data = NSData(contentsOfURL: url!)
    let IMG = UIImage(data: data!)
    let dtA : NSData = NSData(data: UIImagePNGRepresentation(IMG!)!)
    print("download")
    imageArrayNsData.append(dtA)
    indeX++
    print(indeX)
}                   
self.view.userInteractionEnabled = true
myActivityIndicator.stopAnimating()

Don't download synchronously on the main thread. It's never the right thing. Ever. — Avi, Jul 03 '16 at 07:09
What is simple method to download `Asynchronously` image from `URL` wiithout using `Dispatch`and `AlamofireImage` library? Thanks — ZAFAR007, Jul 03 '16 at 07:16
@ZAFAR007 Use NSURLSession. There's many [examples](http://stackoverflow.com/a/37343547/2227743) on SO. — Eric Aya, Jul 03 '16 at 08:17

Zac Kwan · Accepted Answer · 2016-07-03T09:02:06.237

1

To do it Asynchronously, you will have to use dispatch. Infact, AlamofireImage uses dispatch to handle it as well.

In my opinion, you could have your code in a dispatch for queue user initial and update the main queue when completed for the myActivityIndicator and self.view.userInteractionEnabled

dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.rawValue), 0)) { 
  //your download code here

  dispatch_async(dispatch_get_main_queue()) {
    self.view.userInteractionEnabled = true
    myActivityIndicator.stopAnimating()
   }  
}

edited Jul 03 '16 at 09:02

answered Jul 03 '16 at 08:28

Zac Kwan

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`Value of type 'qos_class_t' has no member 'value'` – ZAFAR007 Jul 03 '16 at 08:58
sorry, in swift 2 is changed to `QOS_CLASS_USER_INITIATED.rawValue`. – Zac Kwan Jul 03 '16 at 09:01
Can you please tell me how i can use it on ios 7.0 because it is only available in ios 8. Thanks – ZAFAR007 Jul 10 '16 at 05:37
Can you please send me previous code that you wrote before edit? – ZAFAR007 Jul 10 '16 at 16:00
Hey, the previous code before edit is just without the `.rawValue`. So is just `QOS_CLASS_USER_INITIATED.value` – Zac Kwan Jul 10 '16 at 16:05
I want to run it on minimum ios 7.0 or ios 7.1. Have you any idea how i can run it because i think this is only available for ios8?? – ZAFAR007 Jul 10 '16 at 16:08

Start animating UIActivityIndicator when image downloads throug contentsOfURL synchronous

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