我有一个UIPageviewcontroller，里面有两个控制器。当您滑动到下一个时，我使用viewController参数设置适当的委托。但是我体验到，如果您滑动得太快，则函数viewControllerAfter无法正确更新viewController。最初的滑动应将ViewController的索引从0更新为1，但如果滑动速度过快，则不会这样做。
import UIKit
class WizardPageViewController: UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {
lazy var orderedViewControllers: [UIViewController] = {
return [self.newVc(viewController: "intro"),
self.newVc(viewController: "welcome")]
}()
var pageControl = UIPageControl()
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self
self.delegate = self
configurePageControl()
// This sets up the first view that will show up on our page control
if let firstViewController = orderedViewControllers.first {
setViewControllers([firstViewController],
direction: .forward,
animated: true,
completion: nil)
}
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
let pageContentViewController = pageViewController.viewControllers![0]
self.pageControl.currentPage = orderedViewControllers.index(of: pageContentViewController)!
}
func newVc(viewController: String) -> UIViewController {
return UIStoryboard(name: "Wizard", bundle: nil).instantiateViewController(withIdentifier: viewController)
}
func configurePageControl() {
// The total number of pages that are available is based on how many available colors we have.
pageControl = UIPageControl(frame: CGRect(x: 0,y: UIScreen.main.bounds.maxY - 225,width: UIScreen.main.bounds.width,height: 50))
self.pageControl.numberOfPages = orderedViewControllers.count
self.pageControl.currentPage = 0
pageControl.isEnabled = false
//self.pageControl.tintColor = UIColor.black
self.pageControl.pageIndicatorTintColor = UIColor.gray
self.pageControl.currentPageIndicatorTintColor = UIColor(red:0.647, green:0.192, blue:0.216, alpha:1.00)
self.view.addSubview(pageControl)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
return nil
}
print(orderedViewControllers.index(of: viewController))
let previousIndex = viewControllerIndex - 1
// User is on the first view controller and swiped left to loop to
// the last view controller.
guard previousIndex >= 0 else {
return nil
// Uncommment the line below, remove the line above if you don't want the page control to loop.
// return nil
}
guard orderedViewControllers.count > previousIndex else {
return nil
}
return orderedViewControllers[previousIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
return nil
}
print(orderedViewControllers.index(of: viewController)) // Returns 0 is I swipe too fast, otherwise 1
if let vc = orderedViewControllers[viewControllerIndex] as? WelcomeViewController {
vc.delegate = self
}
let nextIndex = viewControllerIndex + 1
let orderedViewControllersCount = orderedViewControllers.count
// User is on the last view controller and swiped right to loop to
// the first view controller.
guard orderedViewControllersCount != nextIndex else {
return nil
// Uncommment the line below, remove the line above if you don't want the page control to loop.
// return nil
}
guard orderedViewControllersCount > nextIndex else {
return nil
}
return orderedViewControllers[nextIndex]
}
}
答案 0 :(得分：2)
我遇到了完全相同的问题。基本上，它归结为UIPageViewController（确切地说是_UIQueuingScrollView），无法正确更新其视图层次结构。
我注意到UIPageViewController足够聪明，即使页面保持不变也不会添加/删除内容视图（即使它在视图层次结构中的位置不正确，它也会设法解决该问题，因此看起来不错用户）。这就是为什么我添加了PageTrackingView来观察正在（或没有）添加到UIPageViewController视图层次结构中的内容视图的原因。通过跟踪更改是否发生，我可以通过翻转来计算当前索引。因此，目前的解决方法仅适用于 2页。
class PageTrackingView: UIView {
var pageIndexable: PageIndexable?
override func willMove(toSuperview newSuperview: UIView?) {
super.willMove(toSuperview: newSuperview)
if var pageIndexable = pageIndexable {
let newIndex = (pageIndexable.internalIndex == 0) ? 1 : 0
pageIndexable.internalIndex = newIndex
}
//Reset pageIndexable so that the index flip is fired only once
pageIndexable = nil
}
}
protocol PageIndexable {
var internalIndex: Int { get set }
}
class PageViewController: UIPageViewController,
UIPageViewControllerDataSource,
UIPageViewControllerDelegate,
PageIndexable {
private var supportedViewControllers = [UIViewController]()
internal var internalIndex: Int = 0 {
didSet {
if supportedViewControllers.indices.contains(internalIndex) {
//Do something with the actual internalIndex value
} else {
assertionFailure()
}
}
init(transitionStyle style: UIPageViewControllerTransitionStyle = .scroll,
navigationOrientation: UIPageViewControllerNavigationOrientation = .horizontal,
options: [String: Any]? = nil,
viewControllers: [T]) {
supportedViewControllers = viewControllers
if !supportedViewControllers.isEmpty {
let viewController = supportedViewControllers[0]
let trackingView = PageTrackingView(frame: viewController.view.frame)
viewController.view.frame = viewController.view.bounds
trackingView.addSubview(viewController.view)
viewController.view = trackingView
}
super.init(transitionStyle: style,
navigationOrientation: navigationOrientation,
options: options)
}
func pageViewController(_ pageViewController: UIPageViewController,
didFinishAnimating finished: Bool,
previousViewControllers: [UIViewController],
transitionCompleted completed: Bool) {
if !supportedViewControllers.isEmpty, let trackingView = supportedViewControllers[0].view as? PageTrackingView {
trackingView.pageIndexable = self
}
}
override func viewDidLoad() {
super.viewDidLoad()
delegate = self
datasource = self
}
}
答案 1 :(得分：0)
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
guard let index = arrayVCs.index(of: viewController) else {
return nil
}
if index == 0 {
return nil
}
let prevIndex = abs((index - 1) % arrayVCs.count)
return arrayVCs[prevIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
guard let index = arrayVCs.index(of: viewController) else {
return nil
}
if index == arrayVCs.count - 1 {
return nil
}
let nextIndex = abs((index + 1) % arrayVCs.count)
return arrayVCs[nextIndex]
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if let viewController = pageViewController.viewControllers?[0] {
guard let index = arrayVCs.index(of: viewController) else {
return
}
self.segment.selectedSegmentIndex = index
}
}
尝试一下。对我来说有用。