ios - 如何检测容器嵌入 UINavigationController 推送何时显示新 View

Question

我在 Storyboard中创建了 UIViewController (A)，并使用 UINavController 添加了容器。

我嵌入的 UINavController 的根是带有按钮的 UIViewController (B)。

如果我点击按钮，NavController 会显示新的 UIViewController (C)。

所以我有 UINavController -> B -> C。A Controller 如何检测其包含的 NavController 内的 B -> C 转换？

Answer 1

有多种方法可以做到这一点，但最简单的解决方案可能是使用通知中心。每当通知发布时，您都会监听通知，为其指定一个唯一的名称，例如 ViewA 或 ViewB 通知，然后监听具有该名称的通知。检查下面的示例:-

import UIKit

struct NotificationNames {
    static let bViewController
    static let cViewController
}



class AViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Listen for notification of from BViewcontroller
        NotificationCenter.default.addObserver(self, selector: #selector(didLoadBViewController), name: Notification.Name(NotificationNames.bViewController), object: nil)

        // Listen for notification of from CViewcontroller
           NotificationCenter.default.addObserver(self, selector: #selector(didLoadCViewController), name: Notification.Name(NotificationNames.cViewController), object: nil)

    }


    @objc private func didLoadBViewController() {
        print("B ViewController is loaded.")
    }

    @objc private func didLoadCViewController() {
           print("C ViewController is loaded.")
       }

    // Remove notification listeners to save some memory
    deinit {
        NotificationCenter.default.removeObserver(self, name: NotificationNames.bViewController, object: nil)
         NotificationCenter.default.removeObserver(self, name: NotificationNames.cViewController, object: nil)
    }

}


class BViewcontroller: UIViewController {

    // Post notification that B ViewController loaded.
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(true)
        NotificationCenter.default.post(name: NotificationNames.bViewController, object: nil)
    }

}

class CViewController: UIViewController {

     // Post notification that C ViewController loaded.
    override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(true)
        NotificationCenter.default.post(name: NotificationNames.cViewController, object: nil)
     }

}