Ios 从第一页或0索引刷回时如何弹出UIPageViewController？

我知道刷卡默认由

UIPageViewController

管理，并且在此过程中调用了一些回调方法，如

willtransition

，

didFinishAnimating

等

当我们从第一页或第零个索引刷回时，是否可以关闭

UIPageViewController

---

我检查并发现没有为此操作调用任何回调方法。

By design

UIPageViewController

不知道当前视图控制器索引。每次调用

pageViewController（\uquo:viewControllerAfter:）

时，您都可以创建

UIViewController

的新实例，并且向前的页面数将是无限的

我怀疑您向UIPageViewController提供了某种类型的数据源，或者是通过它的数据源，或者是通过

setViewController（uu2;：方向：动画：完成：）

。因此，您有责任跟踪当前显示的

UIViewController

的索引

通过访问

UIPageViewController

的委托中的

previousViewControllers

的第一个元素，可以检查正在显示的视图控制器：

func pageViewController(_ pageViewController: UIPageViewController, 
              didFinishAnimating finished: Bool, 
         previousViewControllers: [UIViewController], 
             transitionCompleted completed: Bool)

---

按设计

UIPageViewController

不知道当前视图控制器索引。每次调用

pageViewController（\uquo:viewControllerAfter:）

时，您都可以创建

UIViewController

的新实例，并且向前的页面数将是无限的

我怀疑您向UIPageViewController提供了某种类型的数据源，或者是通过它的数据源，或者是通过

setViewController（uu2;：方向：动画：完成：）

。因此，您有责任跟踪当前显示的

UIViewController

的索引

通过访问

UIPageViewController

的委托中的

previousViewControllers

的第一个元素，可以检查正在显示的视图控制器：

func pageViewController(_ pageViewController: UIPageViewController, 
              didFinishAnimating finished: Bool, 
         previousViewControllers: [UIViewController], 
             transitionCompleted completed: Bool)

---

我能够达到如下预期效果

1） 将以下属性添加到UIPageViewController子类：

var scrollView: UIScrollView?
var swipeBackPanGestureRecognizer: UIPanGestureRecognizer?

2） 现在将以下代码添加到UIPageViewController子类的viewDidLoad方法：

scrollView = view.subviews.filter{ $0 is UIScrollView }.first as? UIScrollView

if let scrollView = scrollView,
   let popGestureRecognizer = self.navigationController?.interactivePopGestureRecognizer,
   let targets = popGestureRecognizer.value(forKey: "targets") as? NSMutableArray {
    let panGestureRecognizer = UIPanGestureRecognizer()
    panGestureRecognizer.setValue(targets, forKey: "targets")
    panGestureRecognizer.delegate = self
    scrollView.addGestureRecognizer(panGestureRecognizer)
    swipeBackPanGestureRecognizer = panGestureRecognizer
}

基本上，您正在向内置scrollView添加一个新的UIPangEstureRecognitor，它从内置InteractivePopEstureRecognitor接管目标操作，负责刷回（我在这里找到了这个提示：）

3） 最后，您需要实现这两种协议方法。确保在UIPageViewController子类的最后一个结束括号下方添加以下代码，并用适当的子类名称替换“YourPageViewController”：

extension YourPageViewController: UIGestureRecognizerDelegate {
    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        guard let panRecognizer = gestureRecognizer as? UIPanGestureRecognizer,
            panRecognizer == swipeBackPanGestureRecognizer else {
            return true
        }

        guard let currentViewController = self.viewControllers?.first,
            pageViewController(self, viewControllerBefore: currentViewController) == nil else {
            return false
        }

        guard let gestureView = panRecognizer.view else {
            return true
        }

        let velocity = (panRecognizer.velocity(in: gestureView)).x
        return velocity > 0
    }

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        if gestureRecognizer == swipeBackPanGestureRecognizer && otherGestureRecognizer == scrollView?.panGestureRecognizer {
            return true
        } else {
            return false
        }
    }
}

GestureRecognitizerShouldBegin（：）的实现确保只有当我们在第一页（UIPageViewControllerDataSource viewControllerBefore==nil）上是a）时，以及当我们从左向右（velocity>0）时，我们的回扫手势才会激活

---

手势识别器（：shouldberredtofailby:）的实现确保了内置UIPageViewController PangestureRecognitor仅在我们自己的回扫手势识别器出现故障时才会触发。

我能够实现如下预期效果

1） 将以下属性添加到UIPageViewController子类：

var scrollView: UIScrollView?
var swipeBackPanGestureRecognizer: UIPanGestureRecognizer?

2） 现在将以下代码添加到UIPageViewController子类的viewDidLoad方法：

scrollView = view.subviews.filter{ $0 is UIScrollView }.first as? UIScrollView

if let scrollView = scrollView,
   let popGestureRecognizer = self.navigationController?.interactivePopGestureRecognizer,
   let targets = popGestureRecognizer.value(forKey: "targets") as? NSMutableArray {
    let panGestureRecognizer = UIPanGestureRecognizer()
    panGestureRecognizer.setValue(targets, forKey: "targets")
    panGestureRecognizer.delegate = self
    scrollView.addGestureRecognizer(panGestureRecognizer)
    swipeBackPanGestureRecognizer = panGestureRecognizer
}

基本上，您正在向内置scrollView添加一个新的UIPangEstureRecognitor，它从内置InteractivePopEstureRecognitor接管目标操作，负责刷回（我在这里找到了这个提示：）

3） 最后，您需要实现这两种协议方法。确保在UIPageViewController子类的最后一个结束括号下方添加以下代码，并用适当的子类名称替换“YourPageViewController”：

extension YourPageViewController: UIGestureRecognizerDelegate {
    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        guard let panRecognizer = gestureRecognizer as? UIPanGestureRecognizer,
            panRecognizer == swipeBackPanGestureRecognizer else {
            return true
        }

        guard let currentViewController = self.viewControllers?.first,
            pageViewController(self, viewControllerBefore: currentViewController) == nil else {
            return false
        }

        guard let gestureView = panRecognizer.view else {
            return true
        }

        let velocity = (panRecognizer.velocity(in: gestureView)).x
        return velocity > 0
    }

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        if gestureRecognizer == swipeBackPanGestureRecognizer && otherGestureRecognizer == scrollView?.panGestureRecognizer {
            return true
        } else {
            return false
        }
    }
}

GestureRecognitizerShouldBegin（：）的实现确保只有当我们在第一页（UIPageViewControllerDataSource viewControllerBefore==nil）上是a）时，以及当我们从左向右（velocity>0）时，我们的回扫手势才会激活

---

gestureRecognizer（：shouldbererequiredTofailby:）的实现确保了内置的UIPageViewController panGestureRecognizer仅在我们自己的回扫手势识别器出现故障时才会触发。

如果您的

UIPageViewController

位于容器视图中，您需要传递

UINavigationController

或在容器的视图控制器中处理它：

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    self.dataSource = self
    for view in view.subviews
    {
        if let scrollView = view as? UIScrollView
        {
            scrollView.panGestureRecognizer.require(toFail: self.parentNavController!.interactivePopGestureRecognizer!);
        }
    }
    self.parentNavController!.interactivePopGestureRecognizer!.delegate = self
}

func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    return self.parentNavController?.topViewController != self.parent || currentIndex == 0
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.identifier) {
        case "pageview_embed":
        let vc = segue.destination as! MyPageViewController
        vc.parentNavController = self.navigationController
        ...
        break
        ...
    }
    ...
}

在容器视图控制器中：

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    self.dataSource = self
    for view in view.subviews
    {
        if let scrollView = view as? UIScrollView
        {
            scrollView.panGestureRecognizer.require(toFail: self.parentNavController!.interactivePopGestureRecognizer!);
        }
    }
    self.parentNavController!.interactivePopGestureRecognizer!.delegate = self
}

func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    return self.parentNavController?.topViewController != self.parent || currentIndex == 0
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.identifier) {
        case "pageview_embed":
        let vc = segue.destination as! MyPageViewController
        vc.parentNavController = self.navigationController
        ...
        break
        ...
    }
    ...
}

---

如果您的

UIPageViewController

位于容器视图中，则需要传递

UINavigationController

或在容器的视图控制器内处理它：

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    self.dataSource = self
    for view in view.subviews
    {
        if let scrollView = view as? UIScrollView
        {
            scrollView.panGestureRecognizer.require(toFail: self.parentNavController!.interactivePopGestureRecognizer!);
        }
    }
    self.parentNavController!.interactivePopGestureRecognizer!.delegate = self
}

func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    return self.parentNavController?.topViewController != self.parent || currentIndex == 0
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.identifier) {
        case "pageview_embed":
        let vc = segue.destination as! MyPageViewController
        vc.parentNavController = self.navigationController
        ...
        break
        ...
    }
    ...
}

在容器视图控制器中：

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    self.dataSource = self
    for view in view.subviews
    {
        if let scrollView = view as? UIScrollView
        {
            scrollView.panGestureRecognizer.require(toFail: self.parentNavController!.interactivePopGestureRecognizer!);
        }
    }
    self.parentNavController!.interactivePopGestureRecognizer!.delegate = self
}

func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    return self.parentNavController?.topViewController != self.parent || currentIndex == 0
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.identifier) {
        case "pageview_embed":
        let vc = segue.destination as! MyPageViewController
        vc.parentNavController = self.navigationController
        ...
        break
        ...
    }
    ...
}

---

我已经在跟踪索引了，这里的问题是当我们在UIPageViewController的第一页时，我们向右滑动，那么我们有机会得到那个事件吗？啊，好吧，我完全误解了你的问题。我认为一个解决方案可能是遍历

UIPageViewController

，因为它的内部

UIScrollView

，然后检查内容偏移量，查看用户滚动了多远。哦，酷！我会试试：）谢谢，我已经在跟踪索引了，这里的问题是当我们在UIPageViewController的第一页时，我们向右滑动，那么我们有机会得到那个事件吗？啊，好吧，我完全误解了你的问题。我认为一个解决方案可能是遍历

UIPageViewController

，因为它的内部

UIScrollView

，然后检查内容偏移量，查看用户滚动了多远。哦，酷！我试试看：）谢谢