UIScrollView scrollRectToVisible:animated: is there a way that a method can be called when animation ends

Question

Is there a way to know when the animation has end and uiscrollview has come to rest.

Answer 1

Yup use scrollViewDidEndScrollingAnimation

Answer 2

scrollViewDidEndDecelerating: UIScrollView delegate method is called when scrollView stops completely.

Answer 3

You need to cover THREE (!) cases. Thanks, Apple.

// do note that you need all three of the following

public func scrollViewDidEndScrollingAnimation(_ s: UIScrollView) {
    // covers case setContentOffset/scrollRectToVisible
    fingerOrProgrammaticMoveDone()
}

public func scrollViewDidEndDragging(_ s: UIScrollView, willDecelerate d: Bool) {
    if decelerate == false {
        // covers certain cases of user finger
        fingerOrProgrammaticMoveDone()
    }
}

public func scrollViewDidEndDecelerating(_ s: UIScrollView) {
    // covers certain cases of user finger
    fingerOrProgrammaticMoveDone()
}

(Be careful to not forget the extra "if" clause in the middle one.)

Then in fingerOrProgrammaticMoveDone() , do what you need.

A good example of this is the nightmare of handling paged scrolling. It is very, very hared to know what page you are on.

Answer 4

I do it like this because sometimes using the delegate isn't practical for me, like if i'm doing it in UIViewController transition:

[UIView animateWithDuration:0.3 animations:^{
    [scrollView setContentOffset:CGPointMake(0, -scrollView.contentInset.top) animated:NO];
} completion:^(BOOL finished) {
    // This is called when it's complete
}];

Answer 5

Implement UIScrollViewDelegate delegate methods for your UIScrollView the following way:

Use scrollViewDidEndScrollingAnimation: to detect when the scrolling animation concludes when you've initiated the scrolling by calling setContentOffset:animated: or scrollRectToVisible:animated: methods (with animated:YES).

If you want to monitor scroll view motion that's been initiated by touch gestures, use scrollViewDidEndDecelerating: method, which is called when the scrolling movement comes to a halt.