UIView.animate seems to freeze other view updates - ios

Question

I have a UIView that is a countdown clock, which I animate with UIView.animate. There is also a running timer that shows the time on a UILabel, when the timer is fired. When the game is in transition (during the count down), the UILabel stops changing. I've put a "print" statement into the timer function and it shows up as expected.
I've been searching for hints about maybe the UIVIew.animate freezes other views, but I see multiple apps moving views at the same time. Maybe I'm supposed to put things on different thread?
#objc func timerUpdate () {
if gameIsRunning {
let endTime = Date.init()
let difference = endTime.timeIntervalSince(gameClock)
let formattedString = String(format: "%3.1f",kDefaultGameClock - difference)
timerLabel.text = "\(formattedString)"
}
}
private func countDownFrom (x: Int) {
if x != 0 && x > 0 {
UIView.animate(withDuration: 1.0,
delay: 0.0,
usingSpringWithDamping: 0.5,
initialSpringVelocity:1.0,
options: .curveEaseOut,
animations: {
self.successLabel.text = "\(x)"
self.successLabel.transform = self.successLabel.transform.scaledBy(x: 4.0, y: 4.0)
}, completion: {_ in
self.successLabel.transform = self.successLabel.transform.scaledBy(x: 0.250, y: 0.250)
if (x - 1 > 0) {
self.countDownFrom(x: x - 1)
} else {
self.successLabel.text = kDefaultGoodGame
self.successLabel.isHidden = true
self.startTheGame()
self.updateScreen()
}
})
}
}

Answer 1

When I tried your code in an empty project, I was able to update both labels.
If timerLabel isn't being updated, it could be a thread issue. UI updates should be on the main thread.
DispatchQueue.main.async {
self.timerLabel.text = "\(formattedString)"
}
For what it's worth, here is what I have working in an empty project.
#IBOutlet weak var timerLabel: UILabel!
#IBOutlet weak var successLabel: UILabel!
let kDefaultGameClock = 30.0
var gameIsRunning = false
var gameClock = Date()
override func viewDidLoad() {
super.viewDidLoad()
start()
}
func start() {
gameIsRunning = true
countDownFrom(x: 30)
Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(timerUpdate), userInfo: nil, repeats: true)
}
#objc func timerUpdate() {
if gameIsRunning {
let endTime = Date.init()
let difference = endTime.timeIntervalSince(gameClock)
let formattedString = String(format: "%3.1f", kDefaultGameClock - difference)
timerLabel.text = "\(formattedString)" // Could be a main thread issue here?
}
}
private func countDownFrom(x: Int) {
if x != 0 && x > 0 {
UIView.animate(withDuration: 1.0,
delay: 0.0,
usingSpringWithDamping: 0.5,
initialSpringVelocity:1.0,
options: .curveEaseOut,
animations: {
self.successLabel.text = "\(x)"
self.successLabel.transform = self.successLabel.transform.scaledBy(x: 4.0, y: 4.0)
}, completion: {_ in
self.successLabel.transform = self.successLabel.transform.scaledBy(x: 0.250, y: 0.250)
if (x - 1 > 0) {
self.countDownFrom(x: x - 1)
} else {
self.successLabel.text = ""
self.successLabel.isHidden = true
//self.startTheGame()
//self.updateScreen()
}
})
}
}
A little off topic, but you might want to declare your Timer as a variable to invalidate it once you're done updating the timerLabel.