When I pause my timer, then try to start it again, it does not run - ios

Question

I'm building an app in Swift 3. When I press start the first time my timer begins, but when I pause it and try to press start again, the timer does not budge. To give context, the timer, with an amount of time attached to it, is selected from a table. each time the timer load, the start button works initially.
protocol TimerViewControllerDelegate: class {
func viewController(_ controller: ViewController, didFinishEditing item: TaskData)
}
class ViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var timerLabel: UILabel!
#IBOutlet weak var pauseButton: UIButton!
#IBOutlet weak var startButton: UIButton!
#IBOutlet weak var timerTaskName: UILabel!
#IBOutlet weak var timerTimeSetting: UILabel!
#IBOutlet weak var progressView: UIProgressView!
weak var delegate: TimerViewControllerDelegate?
var timerTask: TaskData?
var timer: Timer?
var progressViewSpeed: Double = 0.0
#IBAction func cancel(_ sender: Any) {
timer?.invalidate()
dismiss(animated: true, completion: nil)
delegate?.viewController(self, didFinishEditing: timerTask!)
}
#IBAction func startButtonTapped(_ sender: Any) {
timerTask?.startTime = Date()
runTimer()
if timerTask?.isTaskRunning == true {
runTimer()
self.startButton.isEnabled = false
self.pauseButton.isEnabled = true
} else {
//retrieve start time and run
timerTask?.startTime = Date()
runTimer()
self.startButton.isEnabled = false
self.pauseButton.isEnabled = true
}
}
func runTimer() {
guard timer == nil else {
return
}
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: (#selector(ViewController.updateTimer)), userInfo: nil, repeats: true)
}
#IBAction func pauseButtonTapped(_ sender: UIButton) {
if timerTask?.isTaskRunning == true {
timer?.invalidate()
if let timerTask = timerTask, timerTask.isTaskRunning {
// Calculate the difference between now and when the timerTask was started
let difference = Int(Date().timeIntervalSince(timerTask.startTime!))
timerTask.taskRemaining -= difference
if timerTask.taskRemaining == 0 {
// Do something when there's no time remaining on the task?
}
timerTask.startTime = nil
}
}
else {
timerTask?.startTime = Date()
runTimer()
self.pauseButton.setTitle("Pause",for: .normal)
}
self.startButton.isEnabled = true
self.pauseButton.isEnabled = false
}
/*
#IBAction func resetButtonTapped(_ sender: Any) {
timer.invalidate()
seconds = 60
self.timerLabel.text = timeString(time: TimeInterval(seconds))
if self.resumeTapped == true {
self.resumeTapped = false
self.pauseButton.setTitle("Pause",for: .normal)
}
isTimerRunning = false
pauseButton.isEnabled = false
startButton.isEnabled = true
}
*/
func updateTimer() {
guard let timerTask = timerTask else {
return
}
if timerTask.taskRemaining < 1 {
timer?.invalidate()
timer = nil
//Send alert to indicate "time's up!"
} else {
updateTime()
}
progressViewSpeed = 1 / Double(timerTask.taskRemaining)
progressView.progress += Float(progressViewSpeed)
}
func timeString(time:TimeInterval) -> String {
let hours = Int(time) / 3600
let minutes = Int(time) / 60 % 60
let seconds = Int(time) % 60
return String(format:"%02i:%02i:%02i", hours, minutes, seconds)
}
override func viewDidLoad() {
super.viewDidLoad()
guard let timerTask = timerTask else {
return
}
if timerTask.isTaskRunning {
startButton.isEnabled = false
pauseButton.isEnabled = true
runTimer()
} else {
startButton.isEnabled = true
pauseButton.isEnabled = false
}
timerTaskName.text = timerTask.task
updateTime()
self.progressView.transform = CGAffineTransform.identity.rotated(by: CGFloat.pi / 2).scaledBy(x: 1, y: 150)
}
func updateTime() {
guard let timerTask = timerTask else {
return
}
if let startTime = timerTask.startTime {
// Calculate the difference between now and when the timerTask was started
let difference = Int(Date().timeIntervalSince(startTime))
if timerTask.taskRemaining == difference {
// Do something when there's no time remaining on the task
timer?.invalidate()
timer = nil
}
timerLabel.text = timeString(time: TimeInterval(timerTask.taskRemaining - difference))
} else {
timerLabel.text = timeString(time: TimeInterval(timerTask.taskRemaining))
}
}
}

Answer 1

Once you've invalidated an NSTimer, you can't use it again. You should create the new object.
See here for more From NSTimer Docs
Calling this method requests the removal of the timer from the current run loop; as a result, you should always call the invalidate method from the same thread on which the timer was installed. Invalidating the timer immediately disables it so that it no longer affects the run loop. The run loop then removes and releases the timer, either just before the invalidate method returns or at some later point. Once invalidated, timer objects cannot be reused.

Answer 2

You need to invalidate it and recreate it. "isPaused" bool to keep track of the state
var isPaused = true
var timer: Timer?
#IBAction func pauseResume(sender: AnyObject) {
if isPaused{
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: (#selector(ViewController.updateTimer)), userInfo: nil, repeats: true)
pauseButton.isHidden = false
startButton.isHidden = true
isPaused = false
} else {
pauseButton.isHidden = true
startButton.isHidden = false
timer.invalidate()
isPaused = true
}
}