iPhone - NSTimer not repeating after fire

Question

I am creating and firing a NSTimer with:

ncTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
                                           target:self
                                         selector:@selector(handleTimer:)
                                         userInfo:nil
                                          repeats:YES];
[ncTimer fire];

AND

- (void)handleTimer:(NSTimer *)chkTimer {
    // do stuff
}

I am retaining my timer with:

@property (nonatomic, retain) NSTimer *ncTimer;

For some reason the timer is not repeating. It is firing once only and than never again.

*A stupid question on my part, but it's best to be sure:* I presume you're not invalidating the timer anywhere inside the handleTimer method? — John Parker, Jan 23 '11 at 11:36
No I am not.. the only thing I have to add is that I am firing the timer in the viewDidLoad method — Zigglzworth, Jan 23 '11 at 11:46

score 39 · Answer 1 · edited Oct 25 '13 at 23:31

39

The -fire: method manually fires it once. For a timer to be started and repeat, you have to add it to a runloop using [[NSRunLoop currentRunLoop] addTimer: forMode:]

edited Oct 25 '13 at 23:31

Stunner

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answered Dec 30 '11 at 21:26

Walter

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16

This is correct, but it's simpler to use the `NSTimer` `scheduleTimerWith...` methods instead of manually adding to the run loop. – Benedict Cohen Apr 16 '12 at 11:03

score 29 · Answer 2 · edited Jul 28 '19 at 10:02

29

Got it

Adding timer to mainRunLoop made it working

Here you go:

Objective C:

self.ncTimer = [NSTimer timerWithTimeInterval:2.0 target:self selector:@selector(handleTimer:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];

Swift 2

var ncTimer = NSTimer(timeInterval: 2.0, target: self, selector: Selector("handleTimer"), userInfo: nil, repeats: true)
NSRunLoop.mainRunLoop().addTimer(ncTimer, forMode: NSDefaultRunLoopMode)

Swift 3, 4, 5

var ncTimer = Timer(timeInterval: 2.0, target: self, selector: #selector(self.handleTimer), userInfo: nil, repeats: true)
RunLoop.main.add(ncTimer, forMode: RunLoop.Mode.default)

edited Jul 28 '19 at 10:02

Karen Hovhannisyan

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answered Dec 03 '13 at 08:35

Vaibhav Saran

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Wouldn't Objective C be `NSTimer *ncTimer` instead of `self.ncTimer`? Also, wouldn't you say `addTimer:ncTimer` instead of `addTimer:timer`? I have the power to edit this, but I wanted you to be aware of what needed to be done. – Volomike Jun 22 '16 at 05:06
2

Me too, this worked for me but `scheduleTimerWithTimeInterval` didn't – Husam Aug 30 '16 at 09:30
3

In swift 4: `RunLoop.main.add(timer, forMode: RunLoopMode.defaultRunLoopMode)` – JoKr Apr 24 '18 at 16:05

score 8 · Answer 3 · answered Feb 03 '14 at 02:17

You can also copy your code inside this block, which inserts the creation of the Timer in the main thread.

The code will therefore remain:

dispatch_async(dispatch_get_main_queue(), ^{
  self.ncTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
                 target:self selector:@selector(handleTimer:) userInfo:nil repeats: YES];
});

score 8 · Accepted Answer · answered Jan 23 '11 at 12:02

8

You can't just assign to the timer that you have put as a property in your header. This should work:

self.ncTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
 target:self selector:@selector(handleTimer:) userInfo:nil repeats: YES];

Also: The fire method fires the timer, out of cycle. If the timer is non repeating it is invalidated. After the line that says fire, add this:


BOOL timerState = [ncTimer isValid];
NSLog(@"Timer Validity is: %@", timerState?@"YES":@"NO");

answered Jan 23 '11 at 12:02

Aurum Aquila

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1

"Timer Validity is: YES" but still no luck... the timer is not repeating. What could be the problem here? – Zigglzworth Jan 23 '11 at 12:14
I just made a little test app to see what happened and it worked fine for me with the self. Do you have the @synthesize ncTimer at the top of your implementation? – Aurum Aquila Jan 23 '11 at 12:27
Yeah i got that... I have done this in many other apps and its worked fine so I can't figure out whats wrong here – Zigglzworth Jan 23 '11 at 12:32
7

Ok I found the problem. I was starting the timer in a method called from another class in a separate thread which does not allow the timer to repeat. – Zigglzworth Jan 23 '11 at 12:38
so how can we handle this? How can repeat NSTimer can work from another class? – Vaibhav Saran Dec 03 '13 at 08:24
@VaibhavSaran check my answer at this same question – Danilo Ramirez Feb 04 '14 at 20:12
but I have replied also, see below :) – Vaibhav Saran Feb 05 '14 at 06:05

score 4 · Answer 5 · answered Jun 20 '19 at 07:14

I don't know why but Timer.scheduledTimer method is not working but Timer.init method worked.

self.timer = Timer.init(timeInterval: 10.0, repeats: true, block: { (timer) in
            print("\n--------------------TIMER FIRED--------------\n")
            self.checkForDownload()
        })
RunLoop.main.add(self.timer!, forMode: RunLoopMode.defaultRunLoopMode)

score 3 · Answer 6 · edited May 29 '12 at 20:40

3

Assigning to ncTimer as you have will not initiate the properties retain functionality.

Assuming the declaration is within the member object you will need to do:

self.ncTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(handleTimer:) userInfo:nil repeats:YES]

edited May 29 '12 at 20:40

pablasso

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answered Jan 23 '11 at 11:59

martinws

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I added self. but the problem persists – Zigglzworth Jan 23 '11 at 12:10

score 1 · Answer 7 · answered Jun 01 '20 at 10:24

You could write the same thing in Swift without running in main loops by:

ncTimer = Timer.scheduledTimer(timeInterval: 1.0, 
                               target: self, 
                               selector: #selector(self.handleTimer), 
                               userInfo: nil, 
                               repeats: true)
ncTimer.fire()

score 0 · Answer 8 · answered Oct 22 '20 at 14:58

0

Swift timer with closure:

    let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { _ in
         // Do whatever
    }
    timer.fire()

answered Oct 22 '20 at 14:58

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iPhone - NSTimer not repeating after fire

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