我试图在按下按钮时跳转到特定页面，我制作了一个 ViewController，其中包含 PageViewController 的 ContainerView，这样我就可以在顶部拥有永久按钮。从那里我做:
@IBAction func jump(_ sender: Any) {
PageViewController().jump()
}
这是PageViewController中的Jump函数
func jump() {
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
lastNumber = lastCoinNumber
if let jumpView = viewControllerAtIndex(lastNumber, storyboard: self.storyboard!) {
self.setViewControllers([jumpView], direction: .forward, animated: false, completion: nil)
}
}
由于某种原因，我总是在跳转函数的 ViewControllerAtIndex 部分遇到错误:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value . even if I manually choose an index it does the same.
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!) {
self.setViewControllers([firstViewController], direction: .forward, animated: false, completion: nil)
}
上面是我在 viewDidLoad() 中设置 ViewController 的方式，效果很好，如果我本质上做同样的事情，为什么它不起作用？以下是我如何索引页面并实例化 View Controller ，它们使用相同的单个 ViewController，因此为每个页面创建一个新实例，否则我将创建一个 View Controller 数组。
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) { if !completed { return }
DispatchQueue.main.async() {
self.dataSource = nil
self.dataSource = self
self.pageControl.numberOfPages = (Manager.shared.coins.count)
}
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
self.pageControl.currentPage = Manager.shared.coins.index(of: viewController.dataObject)!
return Manager.shared.coins.index(of: viewController.dataObject)!
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) {
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == -1 {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
我希望这是足够的信息，谢谢。
编辑:
Coin是一个字符串数组，我这样声明:
var last = Manager.shared.coins.last
var lastNumber: Int = 0
然后，jump() 会处理剩下的事情。因此，我获取最后一个对象，找到其索引，然后使用最后一个数字的索引执行 setViewControllers，该索引应与 viewControllerAtIndex 相对应，因为它使用相同的数组来索引和加载页面。
由于某种原因，当我尝试这样做时: var lastCoinNumber:Int = Manager.shared.coins.index(of:last) 它迫使我使用!因为: “可选类型‘Array.Index’的值？” (又名“可选”)未打开；您是否想使用“!”或‘？’？”
我不确定在这方面我做错了什么，以下是硬币的声明方式:
var coins = [""]
编辑:完整代码，PageViewController:
import UIKit
var pageView = PageViewController()
class PageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
//page Control dots
var pageControl = UIPageControl()
var last = Manager.shared.coins.last!
var lastNumber: Int = 0
var viewControllerArray = [UIViewController()]
func configurePageControl() {
// The total number of pages that are available is based on ManagerCoins names array
pageControl = UIPageControl(frame: CGRect(x: 0,y:
UIScreen.main.bounds.maxY - 50,width: UIScreen.main.bounds.width,height:
50))
self.pageControl.numberOfPages = (Manager.shared.coins.count)
self.pageControl.currentPage = 0
self.pageControl.tintColor = UIColor.black
self.pageControl.pageIndicatorTintColor = UIColor.gray
self.pageControl.currentPageIndicatorTintColor = UIColor.white
self.view.addSubview(pageControl)
}
// MARK: Delegate functions
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
self.pageControl.currentPage = Manager.shared.coins.index(of: viewController.dataObject)!
return Manager.shared.coins.index(of: viewController.dataObject)!
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) {
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == -1 {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func jump() {
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
lastNumber = lastCoinNumber
if let jumpView = viewControllerAtIndex(lastCoinNumber, storyboard: self.storyboard!){
self.setViewControllers([jumpView], direction: .forward, animated: false, completion: nil)
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.delegate = self
configurePageControl()
self.dataSource = self
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!){
self.setViewControllers([firstViewController], direction: .forward, animated: false, completion: nil)
}
}
}
编辑:
经过大量研究，这似乎是跳转页面的正确方法，通过调用 setViewControllers，这个答案的第一条评论似乎有同样的问题，它可以很好地设置 viewDidLoad() 上的 View ，但尝试以编程方式导航到基于索引的页面会出错。 https://stackoverflow.com/a/24335008/10058239
最佳答案
我认为它崩溃是因为强制展开:
var lastCoinNumber:Int = Manager.shared.coins.index(of: last!)!
如果硬币是一个集合，您可以使用 .last 来获取最后一个元素，例如:
let numbers = [10, 20, 30, 40, 50]
if let lastNumber = numbers.last {
print(lastNumber)
}
// Prints "50"
关于ios - 如何跳转到UIPageViewController中的特定页面，setViewControllers不起作用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51696625/