Pausing Timer When App Is in Background State Swift

Pausing timer when app is in background state Swift

You have to set an observer listening to when the application did enter background. Add the below line in your ViewController's viewDidLoad() method.

NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("myObserverMethod:"), name:UIApplicationDidEnterBackgroundNotification, object: nil)

Add the below function to receive the notification.

func myObserverMethod(notification : NSNotification) {
    println("Observer method called")

    //You may call your action method here, when the application did enter background.
    //ie., self.pauseTimer() in your case.
}

Happy Coding !!!

Pausing and Resuming a Timer in iOS

I have a custom timer application and dealt with the same issue. There are many ways to address this. You may want to track pausedTime like you do elapsedTime and subtract that from your other variables. This gives you some flexibility as well to show totalTime vs. elapsedTime, etc... My function is quite a bit different, so I retrofitted it to your setup.

Basically, pausing is different because you can pause/resume multiple times. So you need to track previous pauses, and current pause state and subtract from elapsed time (or total time, or whatever you want).

I tested this code and it worked. Give it a try and let me know:

import UIKit

class TimedWorkoutViewController: UIViewController {

  @IBOutlet weak var pauseButton: UIButton!
  @IBOutlet weak var startButton: UIButton!

  var startTime = NSTimeInterval()
  var timer = NSTimer()
  var isTiming = Bool()
  var isPaused = Bool()
  var pausedTime: NSDate?   //track the time current pause started
  var pausedIntervals = [NSTimeInterval]()   //track previous pauses

  override func viewDidLoad() {
    super.viewDidLoad()

  }

  func updatedTimer() {
    let currentTime = NSDate.timeIntervalSinceReferenceDate()
    var pausedSeconds = pausedIntervals.reduce(0) { $0 + $1 }   //calculate total time timer was previously paused
    if let pausedTime = pausedTime {
      pausedSeconds += NSDate().timeIntervalSinceDate(pausedTime)  //add current pause if paused
    }
    var elapsedTime: NSTimeInterval = currentTime - startTime - pausedSeconds  //subtract time paused
    let minutes = Int(elapsedTime / 60.0)

    elapsedTime -= (NSTimeInterval(minutes) * 60)
    let seconds = Int(elapsedTime)

    elapsedTime -= NSTimeInterval(seconds)

    let strMinutes = String(format: "%02d", minutes)
    let strSeconds = String(format: "%02d", seconds)

    workoutTime.text = "\(strMinutes) : \(strSeconds)"
  }

  @IBAction func startButtonTapped(sender: AnyObject) {

    if !timer.valid {

      timer = NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: #selector(TimedWorkoutViewController.updatedTimer), userInfo: nil, repeats: true)
      startTime = NSDate.timeIntervalSinceReferenceDate()
    }

    isTiming = true
    isPaused = false
    pausedIntervals = []  //reset the pausedTimeCollector on new workout
  }

  @IBAction func pauseAndContinueButtonTapped(sender: AnyObject) {

    if isTiming == true && isPaused == false {

      timer.invalidate() //Stop the Timer
      isPaused = true //isPaused
      isTiming = false //Stopped Timing
      pausedTime = NSDate() //asuuming you are starting a brand new workout timer
      pauseButton.setTitle("RESUME", forState: UIControlState.Normal) //Set Button to Continue state

    } else if isTiming == false && isPaused == true {

      let pausedSeconds = NSDate().timeIntervalSinceDate(pausedTime!)  //get time paused
      pausedIntervals.append(pausedSeconds)  // add to paused time collector
      pausedTime = nil   //clear current paused state

      if !timer.valid {

        timer.invalidate()
        //timer = nil

        timer = NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: #selector(TimedWorkoutViewController.updatedTimer),     userInfo: nil, repeats: true)

      }

      isPaused = false
      isTiming = true
      pauseButton.setTitle("PAUSE", forState: UIControlState.Normal) //Set Button to Continue state

    }

  }
}

Stop Time when lock phone in Background Mode

Luke has the right answer, I'm just going to add more detail. In your app delegate you can add

func applicationWillResignActive(application: UIApplication) {
  // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
}

If you need to resume the timer on active you can use this method in your app delegate

func applicationDidBecomeActive(application: UIApplication) {
     // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

For more info on stopping and starting timers, I recommend this link. Best of luck!
How can I pause and resume NSTimer.scheduledTimerWithTimeInterval in swift?

How can I pause and resume NSTimer.scheduledTimerWithTimeInterval in swift?

You need to invalidate it and recreate it. You can then use an isPaused bool to keep track of the state if you have the same button to pause and resume the timer:

var isPaused = true
var timer = NSTimer()    
@IBAction func pauseResume(sender: AnyObject) {     
    if isPaused{
        timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("somAction"), userInfo: nil, repeats: true)
        isPaused = false
    } else {
        timer.invalidate()
        isPaused = true
    }
}

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