I want to create a general UIPageViewController to use in my project. Here is what it like.
When scroll or tap on the number in the titleView, the page view should scroll to the according index, and the according number in title should be highlight. But there is a bug when quickly scroll to next page and scroll back, the title view's status is incorrect.
For example, if I'm in page 2, then scroll to page 3 and quickly scroll back, now I'm in page2 but the button of 3 is highlight.
Here is the key codes:
//Delegaete
func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
willShowPageIndex = getIndex(ofController: pendingViewControllers[0])
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
guard completed else { return }
// track the index
selectedPage = willShowPageIndex
}
fileprivate var selectedPage = 0 {
didSet {
//Change the button's font color, and move the underline
changeShowStatus(oldPage: oldValue, newPage: selectedPage)
}
}
It seems like when quickly scroll page view, the pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) didn't invoke. Maybe posting notification in datasource controller's viewWillAppear could avoid this problem, but I don't want this cause this PageViewController should be general.
Any one have better solution?
Related
So I'm working on an App right now and one of the specs of this app is to have a swipe between views functionality on specific pages kind of like the camera on Instagram.
My current solution is to set the initial view controller as a UIPageViewController which has two view controllers one is the main tab bar controller (first image) for the whole app and the second view controller is the one shown in pink in the image above, and then to enable and disable sliding functionality for the PageViewController depending on whether the current view is meant to have access to the second 'pink' view controller. (PS open to a totally different architecture than this if anyone knows of one, this is just the best I could do given my limited knowledge on iOS)
Normally every thing works fine. However, when I move my finger's in a very particular pattern, the entire app stops functioning. The pattern is shown below:
The pattern is basically:
Swipe slowly to the left a little bit until part of the second 'pink' view controller is showing (image 2 above)
Swipe quickly to the right causing the empty space to the left of the main view controller to show (image 3)
Quickly Let go and let the main view controller fall back into place (image 4)
(*edit - Probably worth noting that if I do this same pattern slowly instead of quickly sliding right and letting go everything works just fine)
(PS if there's a way to upload a screen recording let me know)
Anyways, If I do this just one time, my entire app stops working. Basically every page stops loading data, and any time I click on a button on the main page (eg. the likes button shown in the images) I get an "Unbalanced calls to begin/end appearance transitions for AppName.ViewController" and the new view controller shows up with no data.
Furthermore, as soon as I swipe over to the second page 'pink' view controller and then back to the main app, everything works again.
I don't really know what code is relevant to this problem (spent about 5 hours trying to figure that out with no luck), so I'm just gonna post my UIPageViewController class for now, if you think the problem is coming from somewhere else let me know and I'll post that code.
// MARK: -> Properties
class PageViewController: UIPageViewController {
var pages = [UIViewController]()
}
// MARK: -> Lifecycle
extension PageViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self
setViewController(withIdentifier: "MainTabController")
setViewController(withIdentifier: "SecondaryPage") // The 'Pink' screen
setViewControllers([pages.first!], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)
}
}
// MARK: -> Helpers
fileprivate extension PageViewController {
func setViewController(withIdentifier storyboardIdentifier: String){
let page: UIViewController! = storyboard?.instantiateViewController(withIdentifier: storyboardIdentifier)
storyboard?.configure(viewController: page)
self.pages.append(page)
}
}
// MARK: -> UIPageController Data Source
extension PageViewController: UIPageViewControllerDataSource {
func presentationIndex(for pageViewController: UIPageViewController)-> Int {
return pages.count
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
let cur = pages.index(of: viewController)!
if cur == 0 { return nil }
let prev = abs((cur - 1) % pages.count)
return pages[prev]
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let cur = pages.index(of: viewController)!
if cur == (pages.count - 1) { return nil }
let nxt = abs((cur + 1) % pages.count)
return pages[nxt]
}
}
Update
Not sure what exactly this means but I'm sure it's relevant. I added this extension and method to my PageViewController
extension PageViewController: UIPageViewControllerDelegate {
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
print(completed)
}
}
(and then obviously set the delegate to self in viewDidLoad)
This printed true and false as you would expect except when I swiped in the pattern I described above, in which case it never even fired the method and printed nothing at all.
I have a UIPageViewController that only ever has two UIViewControllers in. There is a UISegmentControl above the UIPageViewController that changes between the segments "new" and "hot" depending on which page the UIPageViewController is on. This works about 90% of the time, however, if I swipe as indicated in this question, the UIPageViewController gets confused on which page it is on. This results in the UISegmentControl saying "new" when actually the "hot" page is being displayed.
Each view controller is assigned a page index (0 or 1) when it's first instantiated. Then the following code changes the segmented control index:
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed,
let index = (pageViewController.viewControllers?.last as? MyCollectionViewController)?.pageIndex,
let pageType = PageType(rawValue: index) {
currentPage = pageType
segmentedControl.selectedSegmentIndex = index
}
}
What's weird is that when the bug is occurring, I print out the pageIndex of the pageViewControllers last viewController and it agrees with the segmentedControl index. Yet on screen, it is 100% not the viewController it's claiming is being shown...
I have the following function which I would like to call whenever the user swipes from one page to another (vertical paging):
func sendNotification (){
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "stopVideo"), object: nil)
print("called")
}
Currently, the function is called whenever the pageAfter or -before is created so to say. The function used to "create" the next/previous page looks like this (in this case it's viewControllerAfter):
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let currentIndexString = (viewController as! MyViewController).index
let currentIndex = indec.index(of: currentIndexString!)
//set if so that next page
if currentIndex! < indec.count - 1 {
let myViewController = MyViewController()
myViewController.index = indec[currentIndex! + 1]
sendNotification() //function is called
return myViewController
}
return nil
}
Since the UIPageViewController somewhat prepares the following pages and going back to the previous page also doesn't call the function (as the view controller does not need to be "created") I do not get the result I want. I was wondering if there is a function in which I can call sendNotification() on completion of the animation. I found a lot of questions regarding jumping to another page but none concerning my problem. I'd really appreciate your help!
You can use the UIPageViewControllerDelegate Functions
func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController])
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool)
As the name of these functions say, the first one will be called, when the user swipes to another page of your PageViewController.
The Second one will be called, when the Transition has completed, which means the user sees the next page after the animation.
In both you can check for changes between the pages.
Also do not forget to check the completed variable of the second function. If the user starts swiping and then does not go to the next page (cause he releases the finger before it or similar) it is false and you do not have your new ViewController.
The array previousViewControllers holds the recently shown controllers where previousViewControllers[0] is probably the one shown before.
For more Information look up the documentation
Maybe it will be good for you to run your notification method in UIPageViewControllerDelegate method documentation documentation :
optional func pageViewController(_ pageViewController: UIPageViewController,
didFinishAnimating finished: Bool,
previousViewControllers: [UIViewController],
transitionCompleted completed: Bool)
I have a UIPageViewController (custom one) inside a Container located in a regular UIViewController. i need to be able to call an event with each Page Change but ONLY if it really did change and not only half way or anything of that sort.
using:
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
is unreliable and not called each time for some reason.
if your answer contains anything about willTransitionToViewControllers or didFinishAnimating please elaborate and not just mention them, since i already know they exist but dont understand the proper way to use them.
Thank you
Use didFinishAnimating it has a completed and finished property so you know the page has actually changed. From the pageViewController you can get the currently displayed page, then get the position of this VC in your model.
First make sure your ViewController adopts UIPageViewControllerDelegate
Set the delegate (e.g. in viewDidLoad)
pageViewController.delegate = self
Then implement the following function:
func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if (completed && finished) {
if let currentVC = pageViewController.viewControllers?.last {
let index = myViewControllers.indexOf(currentVC)
//do something with index
}
}
}
I'm scrolling between different views, which i on button click from the rootViewController would like to render to a image. I'm wondering what is the best approach for this? is it possible to retrieve the visible view from my contentViewController or would i need to recreate the view somehow by getting the visible view index and then access the object equal to this index?
To answer 'is it possible to retrieve the visible view from my contentViewController', not really. You need to set a pageIndex property in your CustomContentViewController. Keep trace of it in the didFinishAnimating method (You can find more robust way in other posts). Or you can directly trace the currentContentViewController
This is just a very simple example
func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
self.currentContentViewController = pageViewController.viewControllers!.last as! CustomContentViewController
self.currentPageIndex = self.currentContentViewController.pageIndex
}
If you want to set a image, then do
#IBAction func buttonTapped(sender: UIButton) {
self.currentContentViewController.imageView.image = UIImage("MyImage.png")
}