UIScrollView pauses NSTimer while scrolling

问题:

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?

回答1:

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.

回答2:

for swift:

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

回答3:

(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;
        }
    }
}