Swift 3 - Activity Indicator delay or not responding - json

Question

I have field and button when you fill the field with content and click the button:
#IBAction func dpSomething(_ sender: UIButton) {
activityIndicator.startAnimating()
activityIndicator.isHidden = false
field.isHidden = true
send.isHidden = true
let url = "http://urlwithjson"
let session = URLSession.shared
DispatchQueue.main.async { [unowned self] in
let task = session.dataTask(with: URL(string: url)!) { (data, response, error) in
if(error==nil){
do {
let jsonData = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! NSDictionary
if((jsonData["response"] as! Int) == 0){
self.responseL.text = "no results"
}
self.activityIndicator.stopAnimating()
self.responseL.isHidden = false
} catch _ {}
}
}
task.resume()
}
}
when I use print it prints me almost immediately the JSON, but activity indicator needs 10-20 secs to disappear or sometimes it doesn't disappear. Can somebody tells me why? And also when I change the text in the label I receive error in console:
This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.
Why this is happening ?

Answer 1

First of all Add the following code after activityIndicator.startAnimating() , this code will hide the activity indicator ones you call self.activityIndicator.stopAnimating():
activityIndicator.hidesWhenStopped = true
Also you are only hiding the activity indicator if the response succeeded, so you may need to hide the indicator when there is an error in catch block and in else block when you get an error from api response
Another point is when you make your request it's not supposed to be in main thread, only in background and then when you need to update the UI then do use main thread , so finally here is the full code you may need:
#IBAction func dpSomething(_ sender: UIButton) {
activityIndicator.startAnimating()
activityIndicator.isHidden = false
activityIndicator.hidesWhenStopped = true
field.isHidden = true
send.isHidden = true
let url = "http://urlwithjson"
let session = URLSession.shared
let task = session.dataTask(with: URL(string: url)!) { (data, response, error) in
if(error==nil){
do {
let jsonData = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! NSDictionary
if((jsonData["response"] as! Int) == 0){
DispatchQueue.main.async {
//Update your UI here
self.responseL.text = "no results"
}
}
DispatchQueue.main.async {
//Update your UI here
self.activityIndicator.stopAnimating()
self.responseL.isHidden = false
}
} catch _ {
// JSONSerialization error might happen so hide the indicator
DispatchQueue.main.async {
//Update your UI here
self.activityIndicator.stopAnimating()
self.responseL.isHidden = false
}
}
}else {
// api response error might happen so hide the indicator
DispatchQueue.main.async {
//Update your UI here
self.activityIndicator.stopAnimating()
self.responseL.isHidden = false
}
}
}
task.resume()
}

Answer 2

You need to only make UI changes on main thread never call Async API call on main thread.
let task = session.dataTask(with: URL(string: url)!) { (data, response, error) in
if(error==nil){
do {
let jsonData = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! NSDictionary
if((jsonData["response"] as! Int) == 0){
self.responseL.text = "no results"
}
DispatchQueue.main.async {
self.activityIndicator.stopAnimating()
self.activityIndicator.isHidden = true
self.responseL.isHidden = false
}
} catch _ {}
}
}
task.resume()