UIScrollView pauses NSTimer while scrolling

Question

I have a UIScrollView that has a series of labels which are rapidly updating numbers (every .06 seconds). While the scroll view is moving, however, the NSTimer is paused and does not continue until after the scrolling and the elastic animation have finished.

How can I avoid this and have the NSTimer run regardless of the state of the scroll view?

score 25 · Accepted Answer · answered Aug 14 '11 at 20:24

25

An easy way to fix this is adding your NSTimer to the mainRunLoop.

[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

To remove a timer from all run loop modes on which it is installed, send an invalidate message to the timer.

answered Aug 14 '11 at 20:24

Iñigo Beitia

6,303
4
40
46

So with this I don't actually have to fire the timer, it's initiated when that line is executed, correct? – Peter Kazazes Aug 14 '11 at 20:25
From the documentation: "You can add a timer to multiple input modes. While running in the designated mode, the receiver causes the timer to fire on or after its scheduled fire date. Upon firing, the timer invokes its associated handler routine, which is a selector on a designated object." – Iñigo Beitia Aug 14 '11 at 20:28

Matt Wyeth · Answer 2 · 2016-02-29T14:03:23.273

1

for swift:

NSRunLoop.mainRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)

edited Feb 29 '16 at 14:03

answered Feb 29 '16 at 13:51

Matt Wyeth

1,124
2
10
19

`RunLoop.main.add(timer, forMode: RunLoop.Mode.common)` – tyler Dec 17 '21 at 17:32

score 0 · Answer 3 · answered Nov 25 '14 at 16:56

(Swift) An alternative: You can use a GCD-based timer system like this one:

class GCDTimer {

    private var _timer : dispatch_source_t?

    init() {

    }

    private func _createTheTimer(interval : Double, queue : dispatch_queue_t, block : (() -> Void)) -> dispatch_source_t
    {
        let timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
        if (timer != nil)
        {
            dispatch_source_set_timer(timer, dispatch_time(DISPATCH_TIME_NOW, Int64(interval * Double(NSEC_PER_SEC))), UInt64(interval * Double(NSEC_PER_SEC)), (1 * NSEC_PER_SEC) / 10);
            dispatch_source_set_event_handler(timer, block);
            dispatch_resume(timer);
        }
        return timer;
    }


    func start(interval : Double, block : (() -> Void))
    {
        let queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

        _timer = _createTheTimer(interval, queue: queue, block: block)

    }

    func stop()
    {
        if (_timer != nil) {
            dispatch_source_cancel(_timer!);
            _timer = nil;
        }
    }
}

Here's how you would use it: `var myInterval:GCDTimer = GCDTimer() myInterval.start(1.0) { println("lol") }` — Thyselius, Apr 18 '15 at 20:02
If you want to make an update to a UI element using this timer, you must do this on the main thread, like this: `dispatch_async(dispatch_get_main_queue(), { self.myUIImageView.image = UIImage(data: data as! NSData)! })` — Thyselius, Apr 18 '15 at 20:43

UIScrollView pauses NSTimer while scrolling

3 Answers3

Linked

Related