I want to implement a Refresh Control on my horizontal UICollectionView, but I can't figure out how to implement it. I essentially want to be able to swipe right one the first cell (cells take up the whole screen) and refresh. I've been searching online and found a cocoa pod that is too outdated, and found a way to add one vertically (not what I want), but nothing what I described. Is it even possible to do something like this?
Here's an attempt on the implementation:
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset
let inset = scrollView.contentInset
let y: CGFloat = offset.x - inset.left
let reload_distance: CGFloat = -80
if y < reload_distance{
shouldReload = true
}
}
override func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if let _ = scrollView as? UICollectionView {
currentlyScrolling = false
if shouldReload {
reload()
}
}
}
func reload(){
print("RELOADING")
}
the third party library mentioned ended up working. Downloading via cocoa pods was giving errors but downloading the code and adding the .h files to my bridging header allowed it to work. Here's the repo: https://github.com/hoang-tran/HTPullToRefresh
Related
I have a UIScrollView which scrolls automatically by setting its content offset within via a UIViewPropertyAnimator. The auto-scrolling is working as expected, however I also want to be able to interrupt the animation to scroll manually.
This seems to be one of the selling points of UIViewPropertyAnimator:
...dynamically modify your animations before they finish
However it doesn't seem to play nicely with scroll views (unless I'm doing something wrong here).
For the most part, it is working. When I scroll during animation, it pauses, then resumes once deceleration has ended. However, as I scroll towards the bottom, it rubber bands as if it is already at the end of the content (even if it is nowhere near). This is not an issue while scrolling towards the top.
Having noticed this, I checked the value of scrollView.contentOffset and it seems that it is stuck at the maximum value + the rubber banding offset. I found this question/answer which seems to be indicate this could be a bug with UIViewPropertyAnimator.
My code is as follows:
private var maxYOffset: CGFloat = .zero
private var interruptedFraction: CGFloat = .zero
override func layoutSubviews() {
super.layoutSubviews()
self.maxYOffset = self.scrollView.contentSize.height - self.scrollView.frame.height
}
private func scrollToEnd() {
let maxOffset = CGPoint(x: .zero, y: self.maxYOffset)
let duration = (Double(self.script.wordCount) / Double(self.viewModel.wordsPerMinute)) * 60.0
let animator = UIViewPropertyAnimator(duration: duration, curve: .linear) {
self.scrollView.contentOffset = maxOffset
}
animator.startAnimation()
self.scrollAnimator = animator
}
extension UIAutoScrollView: UIScrollViewDelegate {
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
// A user initiated pan gesture will begin scrolling.
if let scrollAnimator = self.scrollAnimator, self.viewModel.isScrolling {
self.interruptedFraction = scrollAnimator.fractionComplete
scrollAnimator.pauseAnimation()
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if let scrollAnimator = self.scrollAnimator, self.viewModel.isScrolling {
scrollAnimator.startAnimation()
}
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if let scrollAnimator = self.scrollAnimator, self.viewModel.isScrolling {
scrollAnimator.startAnimation()
}
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
switch scrollView.panGestureRecognizer.state {
case .changed:
// A user initiated pan gesture triggered scrolling.
if let scrollAnimator = self.scrollAnimator {
let fraction = (scrollView.contentOffset.y - self.maxYOffset) / self.maxYOffset
let boundedFraction = min(max(.zero, fraction), 1)
scrollAnimator.fractionComplete = boundedFraction + self.interruptedFraction
}
default:
break
}
}
}
Is there anywhere obvious I'm going wrong here? Or any workarounds I can employ to make the scroll view stop rubber banding on scroll downwards?
You can add tap Gesture Recognizer and call this function,
extension UIScrollView {
func stopDecelerating() {
let contentOffset = self.contentOffset
self.setContentOffset(contentOffset, animated: false)
}
}
I have a UICollectionView called dayPicker that scrolls horizontally, and lets you select the day of the month. When the user stops scrolling (scrollViewDidEndDecelerating), I want the app to do something with that day, accessible from the cell's label. All of the answers I have seen online are similar to this: https://stackoverflow.com/a/33178797/9036092
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
var someCell : UICollectionViewCell = collectionView.visibleCells()[0];
// Other code follows...
}
When I try to access collectionView from inside the scrollViewDidEndDecelerating function, I get a Ambiguous use of collectionView error. When I substitute the actual name of my UICollectionView (dayPicker), it errors out with "Unexpectedly found nil while implicitly unwrapping an Optional value".
My question is: how do you get to collectionView from inside the scrollViewDidSomething function? Currently my scrollViewDidEndDecelerating function is inside a UICollectionViewDelegate in my view controller, and I have also tried putting it in a UIScrollViewDelegate extension.
Current code:
extension PageOneViewController: UICollectionViewDelegate {
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let centerPoint = CGPoint(x: UIScreen.main.bounds.midX, y: scrollView.frame.midY)
print(centerPoint) // Successfully prints the same center point every time scrolling stops
let indexPath = collectionView.indexPathForItem(at: centerPoint) // Ambiguous error
let indexPath = dayPicker.indexPathForItem(at: centerPoint) // Fatal error
}
}
Screenshot of scrollable UICollectionView in question:
I also have another method of when the user taps on the day, and it is working flawlessly. Trying to complete the experience with the scrolling ending.
Xcode 11.4.1/Swift 5
I figured it out, for those who come across this thread looking for the same answer. Big thanks to this answer here for a different issue: https://stackoverflow.com/a/45385718/9036092
The missing ingredient was to cast scrollView as a UICollectionView so that you can access the collectionView's cell properties.
Working code:
extension PageOneViewController: UICollectionViewDelegate {
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let collectionView = scrollView as! UICollectionView // This is crucial
let centerPoint = CGPoint(x: UIScreen.main.bounds.midX, y: scrollView.frame.midY)
let indexPath = collectionView.indexPathForItem(at: centerPoint)
let centerCell = collectionView.cellForItem(at: indexPath!) as! MyCustomCell
let selectedDay = centerCell.dayLabel.text //
print(selectedDay) // Prints the value of the day in the center of the collectionView, as a string
}
}
Update:
I belive it may not be possible given the folowing line in apples documentation:
When the user drags the top of the scrollable content area downward
Found here.
Let me know if there is a way to do this.
I am trying to make it so that when the user swipe left (the way you swipe up in many apps with tableViews to reload) in a collection view it will show a loading icon and reload data (the reload data part I can handle myself).
How can I detect this so I can call a reloadData() method?
Note: I am using a UICollectionView which only has one column and x rows. At the first cell if the user swipes left it should show a loading icon and reload data.
I am looking for a way to detect the slide left intended to reload.
What I have tried:
let refreshControl = UIRefreshControl()
override func viewDidLoad() {
super.viewDidLoad()
viewDidLoadMethods()
refreshControl.tintColor = .black
refreshControl.addTarget(self, action: #selector(refresh), for: .valueChanged)
collectionView.addSubview(refreshControl)
collectionView.alwaysBounceHorizontal = true
But this only works vertically.
I solved this problem with the following, but I should note that there is no default fucntionality like there is for vertical refresh:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset
let inset = scrollView.contentInset
let y: CGFloat = offset.x - inset.left
let reload_distance: CGFloat = -80
if y < reload_distance{
shouldReload = true
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if let _ = scrollView as? UICollectionView {
currentlyScrolling = false
if shouldReload {
baseVC.showReloading()
reloadCollectionView()
}
}
}
I want to stop backward scrolling on ScrollView after user scrolls to the next page. How can I do that.
I tried the following two codes, but the first one does not have any effect
self.scrollView.contentOffset = CGPointMake(self.view.frame.width,0)
and the second only disables the forward scrolling.
self.scrollView.contentSize = CGSizeMake( 2 * scrollWidth, scrollHeight);
To disable scrolling in one direction you implement the UIScrollViewDelegate method scrollViewDidScroll and put your logic there. For instance this TableViewController can only ever scroll down, because if the user tries to scroll up, we just overwrite the contentOffset, effectively undoing their scroll before they see it.
class ViewController: UITableViewController {
var lastScrollPosition = CGPoint.zero
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView.contentOffset.y > lastScrollPosition.y else {
scrollView.setContentOffset(lastScrollPosition, animated: false)
return
}
lastScrollPosition = scrollView.contentOffset
}
}
If your cell is equal in size to your screen, you can apply the following option, which is very smooth:
var lastScrollPosition = CGPoint.zero
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if scrollView.contentOffset.x == lastScrollPosition.x + UIScreen.main.bounds.width {
lastScrollPosition.x += UIScreen.main.bounds.width
}
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView.contentOffset.x > lastScrollPosition.x else {
scrollView.setContentOffset(lastScrollPosition, animated: false)
return
}
}
I have a UICollectionViewController (embedded in a NavigationViewController), which scrolls a UICollectionView horizontally via paging through some sections:
if let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
flowLayout.scrollDirection = .horizontal
flowLayout.minimumLineSpacing = 0
}
collectionView?.backgroundColor = .white
collectionView?.register(FeedCell.self, forCellWithReuseIdentifier: cellId)
//collectionView?.contentInset = UIEdgeInsetsMake(MenuBar.height, 0, 0, 0)
//collectionView?.scrollIndicatorInsets = UIEdgeInsetsMake(MenuBar.height, 0, 0, 0)
collectionView?.isPagingEnabled = true
Each section or page contains another UICollectionView (inside the FeedCell) which scrolls vertically through some UICollectionViewCells.
Inside the UICollectionViewController, I set
navigationController?.hidesBarsOnSwipe = true
which was working as long as there was only one UICollectionView. But since the (Top)CollectionView is scrolling horizontally and is containing additional (Sub)CollectionView, that are scrolling vertically, this feature seems not to work any longer.
I would like the NavigationBar to hide when the (Sub)CollectionView is scrolling vertically. Is there any hack to achieve this?
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if let navigationBar = self.navigationController?.navigationBar {
let clampedYOffset = contentOffset.y <= 0 ? 0 : -contentOffset.y
navigationBar.transform = CGAffineTransform(translationX: 0, y: clampedYOffset)
self.additionalSafeAreaInsets.top = clampedYOffset
}
}
This is a solution that I came up with. Basically modify the transform of the NavigationBar to move it out the way when necessary. I also modify the additionalSafeAreaInset, as this will automatically shift all your content up to fill the space left by the navigation bar.
This function will be called as part of the UICollectionViewDelegate protocol.
This was suitable for my purposes - but if you want the navigation bar to appear when the user rapidly scrolls up (like in safari) you will have to add some additional logic.
Hope this helps!
You can try the code like this (Swift 3.0):
extension ViewController: UICollectionViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let isScrollingUp = scrollView.contentOffset.y - lastY > 0
lastY = scrollView.contentOffset.y
self.navigationController?.setNavigationBarHidden(isScrollingUp, animated: true)
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if !decelerate {
// show navigation bar ?
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
// show navigationBar ?
}
}