如何关闭当前的 ViewController 并更改为 Swift 中的新 ViewController？

Question

我是 iOS swift 的新手。我有三个ViewController。页面 A 是根控制器，它将呈现给页面 B。它在页面 B 中有一个计时器。 5秒后，View会从page-B变为page-C，同时关闭page-B

在ViewControll-B

class AViewController: UIViewController {

    var timer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()

        //set the timer , and chagne view to C ViewController
        Timer.scheduledTimer(timeInterval: 5,
                             target: self,
                             selector: #selector(self.changeToAnswerView),
                             userInfo: nil,
                             repeats: false)
    }


    @objc func changeToAnswerView() {
        dismissLoader()
    }

    func dismissLoader() {
        dismiss(animated: true) {
            print("Dismissing Loader view Controller")
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        //change view to Answer ViewController
        let filterVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "CViewControllerID")
        filterVC.modalPresentationStyle = UIModalPresentationStyle.custom
        self.present(filterVC, animated: true, completion: nil)
    }

}

计时器执行 5 秒后，BViewController 将自行关闭并呈现给 BViewController。

但是会出现如下错误：

whose view is not in the window hierarchy

我是不是漏了什么？

问题： 如何在 Swift 中关闭当前的 ViewController 并更改为新的 ViewController？

提前致谢。

Answer 1

您正在尝试使用视图控制器的引用（实例），它将不再存在于内存中。

试试这个

if let presentingVC = self.presentingViewController {
        let filterVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "CViewControllerID")
        filterVC.modalPresentationStyle = UIModalPresentationStyle.custom
        presentingVC.present(filterVC, animated: true, completion: nil)
}

注意：在当前视图控制器被关闭后，显示一个新的视图控制器 (filterVC)。一个视图控制器一次只能显示一个视图控制器（如果您选择模态显示）。延迟1秒后执行此操作..

编辑

试试这个编辑过的代码。

Class AViewController: UIViewController {

    var timer: Timer?
    var presentingVC: UIViewController?
    override func viewDidLoad() {
        super.viewDidLoad()

        //set the timer , and chagne view to C ViewController
        Timer.scheduledTimer(timeInterval: 5,
                             target: self,
                             selector: #selector(self.changeToAnswerView),
                             userInfo: nil,
                             repeats: false)
    }


    @objc func changeToAnswerView() {
        dismissLoader()
    }

    func dismissLoader() {
        dismiss(animated: true) {
            print("Dismissing Loader view Controller")
        }
    }

    override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
        //change view to Answer ViewController
        if let presentingVC = self.presentingViewController {
           self.presentingVC = presentingVC
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        //change view to Answer ViewController
        super.viewWillDisappear(animated)
       if let presentingVC = self.presentingVC {

        let filterVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "CViewControllerID")
        filterVC.modalPresentationStyle = UIModalPresentationStyle.custom
        presentingVC?.present(filterVC, animated: true, completion: nil)

      } else {
         print("Presenting View controller is nil")
      }
    }

}

Answer 2

尝试将 dismissLoader 函数更改为类似以下内容：

func dismissLoader() {
    dismiss(animated: true) {
        print("Dismissing Loader view Controller")
        if let presentingController = self.presentingViewController {
            let filterVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "BViewControllerID")
            filterVC.modalPresentationStyle = UIModalPresentationStyle.custom
            presentingController.present(filterVC, animated: true, completion: nil)
        }
    }
}

并删除 viewWillDisappear 函数。

问题是您试图在被解雇后（即从 window 层次结构中删除）从加载程序中呈现 BViewController，但此时不存在。

因此，解决方案是您可以获得对呈现加载程序的呈现视图控制器的引用，它将在关闭加载程序后出现并从那里呈现新的视图控制器。

Answer 3

在你的 B 视图控制器中，在它被解雇后，在它的完成处理程序中

 self.dismiss(animated: true) {
     if let presentingVC = self.presentingViewController {
        present c view controller here
     }
 }

以上是一种方法，另一种方法是通过委托

在视图控制器中：

if let bVC = self.storyboard.instantiateViewController(withIdentifier: B.controllerIdentifier) as? B  {

        bVC.delegate = self
        self.present(bVC, animated: true, completion: nil)
    }

在 B 视图控制器中

为协议添加委托方法

protocol BProtocol: class {
    func didClose()
}

并在 B 中解雇

 var delegate:  BProtocol?
self.dismiss(animated: true) {
     self.delegate?.didClose()
 }

此委托将由 A ViewController 实现为

extension AViewController: BProtocol {
    func didClose() {
        //present C
    }
}

Answer 4

这是您可以尝试的工作代码

您的控制器已被解雇并倾向于创建一个新控制器

import UIKit

class pdfVC: UIViewController
{

    var timer : Timer?

    override func viewDidLoad()
    {
        super.viewDidLoad()
        timer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(pdfVC.timerAction), userInfo: nil, repeats: false)
    }

    @objc func timerAction()
    {
        if timer != nil {
            timer?.invalidate()
            dismiss(animated: true, completion: {
                print("Dismissed")
            })
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        if self.isBeingDismissed {
            let filterVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "demoViewController")
            filterVC.modalPresentationStyle = UIModalPresentationStyle.custom
            print("called")
            self.presentingViewController?.present(filterVC, animated: true, completion: nil)
        }
    }
}

输出

如何关闭当前的 ViewController 并更改为 Swift 中的新 ViewController？

How to dismiss the current ViewController and change to the new ViewController in Swift?

viewcontroller

ios

swift

编辑