UINavigationControllerDelegate的didShowViewController方法被调用了两次 [英] UINavigationControllerDelegate‘s didShowViewController method was called twice

问题描述

class ViewController: UIViewController, UINavigationControllerDelegate {

      override func viewDidLoad() {
         super.viewDidLoad()
         navigationController!.delegate = self
      }

      func navigationController(navigationController: UINavigationController, didShowViewController viewController: UIViewController, animated: Bool) {
         print("showViewController")
      }

      func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
         print("sss")
      }

      func update() {
         let vc = SecondViewController()
         navigationController!.pushViewController(vc, animated: true)
      }
}

这是我演示的第一个控制器，在控制台中：

this is the first controller of my demo , and in console:

sss
showViewController
showViewController

两次调用didShowViewController。
我不确定发生了什么

the "didShowViewController" was called twice. I'm not sure what's going on

-----------------一些测试---- ------------------

-----------------some test----------------------

我在控制器的这些方法中添加一些日志：loadView，viewDidLoad，viewWillAppear，viewDidAppear ，以及这些日志的顺序是：

I add some log in these method of controller : loadView,viewDidLoad ,viewWillAppear,viewDidAppear , and the order of these log is:

loadView
viewDidLoad
viewWillAppear
will:<NaviDemo.ViewController: 0x7fe8c9533050>
<NaviDemo.ViewController: 0x7fe8c9533050>
viewDidAppear
<NaviDemo.ViewController: 0x7fe8c9533050>

推荐答案

覆盖 viewDidLoad（ ..）的 UIViewController 类，你应该总是包含 super.viewDidLoad（），或者您可能会遇到意外行为（例如，视图控制器在预期一次时显示两次）。

When overriding the viewDidLoad(..) of the UIViewController class, you should always include the super.viewDidLoad(), or you might get unexpected behaviour (e.g., a view controller being shown twice when once is expected).

尝试添加 super.viewDidLoad（ ）到您的覆盖viewDidLoad（...）：

override func viewDidLoad() {
    super.viewDidLoad()

    // delegates
    navigationController!.delegate = self
}

您的日志是否仍然显示您的视图控制器显示两次？

Do your log still show your view controller being shown twice?

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