Multiple animations on imageView inside scrollView - ios

Question

I have UIScrollView inside which I have an ImageView. What I am trying to achieve is:
- zoom-in image to fit full height of the screen when user taps and zoom-out when user taps again,
- start automatically first animation which is scrolling to the right side of the image,
- after that, start second animation which is scrolling to the middle of the image,
- at last start again the animation scrolling to the right side of the image.
I would like to achieve the impression of image floating on the screen. User cannot scroll the image by himself.
I have already done the part with zooming, but the problem I have is with animations. I have tried something like this, where offset, middleOffset and endOffset are CGPoints:
override func viewDidLoad() {
super.viewDidLoad()
scrollView.delegate = self
setupGestureRecognizer()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(true)
scrollView.panGestureRecognizer.isEnabled = false
scrollView.pinchGestureRecognizer?.isEnabled = false
}
fileprivate func updateMinZoomScaleForSize(size: CGSize) {
let widthScale = size.width / imageView.bounds.width
let heightScale = size.height / imageView.bounds.height
let minScale = min(widthScale, heightScale)
let maxHeightScale = view.frame.height / imageView.bounds.height
scrollView.maximumZoomScale = maxHeightScale
scrollView.minimumZoomScale = minScale
scrollView.zoomScale = minScale
}
fileprivate func updateConstraintsForSize(size: CGSize) {
let yOffset = max(0, (size.height - imageView.frame.height) / 2)
imageViewTopConstraint.constant = yOffset
imageViewBottomConstraint.constant = yOffset
let xOffset = max(0, (size.width - imageView.frame.width) / 2)
imageViewLeadingConstraint.constant = xOffset
imageViewTrailingConstraint.constant = xOffset
view.layoutIfNeeded()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
updateMinZoomScaleForSize(size: view.bounds.size)
}
func setupGestureRecognizer() {
let singleTap = UITapGestureRecognizer(target: self, action: #selector(self.handleSingleTap(recognizer:)))
singleTap.numberOfTapsRequired = 1
scrollView.addGestureRecognizer(singleTap)
}
func handleSingleTap(recognizer: UITapGestureRecognizer) {
if (scrollView.zoomScale > scrollView.minimumZoomScale) {
scrollView.setZoomScale(scrollView.minimumZoomScale, animated: true)
} else {
scrollView.setZoomScale(scrollView.maximumZoomScale, animated: true)
}
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
UIView.animate(withDuration: 1, delay: 0.3, options: [], animations: {
scrollView.setContentOffset(offset, animated: false)
}, completion: { _ in
UIView.animate(withDuration: 1, delay: 0.3, options: [], animations: {
scrollView.setContentOffset(middleOffset, animated: false)
}, completion: { _ in
UIView.animate(withDuration: 1, delay: 0.3, options: [], animations: {
scrollView.setContentOffset(endOffset, animated: false)
}, completion: nil)
})
})
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imageView
}
func scrollViewDidZoom(_ scrollView: UIScrollView) {
updateConstraintsForSize(size: view.bounds.size)
}
Howewer it does not work. First animation loads after image is zoomed in, but then it stops (it does not crash). It seems like animation is not finished because I cannot zoom-out image when tapping again.

Answer 1

Ok, I found out that animation blocks cannot be inside of scrollViewDidScroll delegate method. I put them inside handleSingleTap function and then it works as it should.