How to detect when a UIScrollView has finished scrolling In Swift

Question

There was, by all accounts, an excellent solution to this problem in Obj-C presented by Ashley Smart (How to detect when a UIScrollView has finished scrolling).

-(void)scrollViewDidScroll:(UIScrollView *)sender 
{   
[NSObject cancelPreviousPerformRequestsWithTarget:self];
    //ensure that the end of scroll is fired.
    [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:nil afterDelay:0.3]; 

...
}

-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
    [NSObject cancelPreviousPerformRequestsWithTarget:self];
...
}

I need a solution, however, in Swift.

It appears that the excellent delay function, contributed by Matt (dispatch_after - GCD in swift?) is likely to help.

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

and implemented as ...

delay(0.4) {
    // do stuff
}

but I've still not put it together. Any help?

Answer 1

You need to check whether the user has stopped dragging and if the view is still decelerating after the user stopped dragging:

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    if collectionView.isDecelerating == false {
        // Perform whichever function you desire for when scrolling has stopped
    }
}

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    // Perform whichever function you desire for when scrolling has stopped
}

Answer 2

The delegate method tells you when finished

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
    self.stoppedScrolling()
}

func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    if !decelerate {
        self.stoppedScrolling()
    }
}

func stoppedScrolling() {
    println("Scroll finished")
}