How to change the NSTimeInterval of an NSTimer aft

问题:

I'm making an app in swift 2 where there is two timers. After 10 seconds I would like another timer to go faster. I have tried doing it like this but it didn't work (I'm trying to change the var time to 1):

@IBOutlet var displayTimeLabel: UILabel!
var startTimer = NSTimeInterval()
var timer = NSTimer()
var timer2:NSTimer = NSTimer()    
var time = 2.0
@IBAction func Start(sender: UIButton) {
    if !timer2.valid {
        timer2 = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: "updateTime", userInfo: nil, repeats: true)
        startTimer = NSDate.timeIntervalSinceReferenceDate()
    }
    timer = NSTimer.scheduledTimerWithTimeInterval(time, target: self, selector: "timer:", userInfo: nil, repeats: true)
}
func timer(timer: NSTimer){
//code
}
func updateTime() {        
    if displayTimeLabel.text >= "00:10.00"{
     print("00:10.00") //works
     time = 1 // trying to execute code after 10 seconds(doesn't work)
    }
    let currentTime = NSDate.timeIntervalSinceReferenceDate()
    var elapsedTime: NSTimeInterval = currentTime - startTimer
    let minutes = UInt8(elapsedTime / 60.0)
    elapsedTime -= (NSTimeInterval(minutes) * 60)
    let seconds = UInt8(elapsedTime)
    elapsedTime -= NSTimeInterval(seconds)
    let fraction = UInt8(elapsedTime * 100)
    let strMinutes = String(format: "%02d", minutes)
    let strSeconds = String(format: "%02d", seconds)
    let strFraction = String(format: "%02d", fraction)
    displayTimeLabel.text = "\(strMinutes):\(strSeconds).\(strFraction)"
}

If I write print(time) in func timer, after ten seconds it will print 1 instead of 2 but it will still be repeating every two second. Please help. To be clear, I want to be able to change time to 1 instead of 2 after ten seconds. I also don't want to invalidate the timers. The timers are also on repeat = true. Thanks in advance... Anton

回答1:

A few of things.

First, you can't change the time interval of a repeating NSTimer - you need to invalidate the first timer and schedule a new one for the new interval.

Second a >= comparison on a string won't work for what you are trying to achieve.

Finally, you have fallen into the same bad habit as many Swift programmers and initialised your timer variables needlessly only to subsequently throw those timers away. You should use either an optional or an implicitly unwrapped optional

@IBOutlet var displayTimeLabel: UILabel!
var startTime:NSDate?
var timer : NSTimer?
var timer2: NSTimer?  
var time = 2.0

@IBAction func Start(sender: UIButton) {
    if (self.timer2 == nil) {
        self.time=2.0 
        self.timer2 = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: "updateTime", userInfo: nil, repeats: true)
        self.startTime = NSDate()
        self.timer = NSTimer.scheduledTimerWithTimeInterval(time, target: self, selector: "timer:", userInfo: nil, repeats: true)
    }
}

func timer(timer: NSTimer){
//code
}
func updateTime() {        
    let currentTime = NSDate.timeIntervalSinceNow()
    var elapsedTime = -self.startTime!.timeIntervalSinceNow()
    if (elapsedTime >10.0 && self.time==2.0) {
       timer.invalidate()
       self.time=1.0
       self.timer = NSTimer.scheduledTimerWithTimeInterval(time, target: self, selector: "timer:", userInfo: nil, repeats: true)
    }

    let minutes = UInt8(elapsedTime / 60.0)
    elapsedTime -= (NSTimeInterval(minutes) * 60)
    let seconds = UInt8(elapsedTime)
    elapsedTime -= NSTimeInterval(seconds)
    let fraction = UInt8(elapsedTime * 100)
    displayTimeLabel.text = String(format: "%02d:%02d.%02d", minutes,seconds,fraction)
}

回答2:

Just setting time = 1 will not modify timer.

The timeInterval of a timer can not be changed. Your only options are to create a new timer or start it with a timeInterval of 1 and just do nothing every other time timer() is called until the 10 sec have passed.