仅当特定ViewController处于前台时，iOS Swift调用函数

Question

In my app I am having two view controller viewcontroller1 and viewcontroller2 . In view controller1 I am having one function called UpdateView() I need to call this function for every 60 seconds and I did it using DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 60) . My problem is I want to run this function only when viewcontroller1 is in foreground, when user moved to viewcontroller2 I don't want to run this function any more. How to solve this?

Answer 1

您应该在viewDidDisappear中停止计时器，并在ViewController1中的viewDidAppear中启动计时器逻辑。

Answer 2

You can do this easily with a Timer . Inside viewWillAppear method start the timer and inside the viewWillDisappear stop or pause the timer.

var myTimer:Timer!
var myTimeInterval:TimeInterval = 60

override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        myTimer = Timer.init(fire: Date(), interval: myTimeInterval, repeats: true, block: { (aTimer) in
            //call the functio you want
            UpdateView()
        })
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        myTimer.invalidate()
    }