ios - UINavigationControllerDelegate 的 didShowViewController 方法被调用了两次

Question

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 Controller ，在控制台中:

sss
showViewController
showViewController

“didShowViewController”被调用了两次。我不确定发生了什么

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

我在 Controller 的这些方法中添加了一些日志:loadView,viewDidLoad,viewWillAppear,viewDidAppear，这些日志的顺序是:

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

Answer 1

我在我的代码中遇到了同样的问题。我能够通过等到 viewDidAppear 设置导航委托(delegate)而不是在 viewDidLoad 中设置它来解决它。将其翻译成您的示例:

override func viewDidLoad() {
   super.viewDidLoad()
}

// ...

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    navigationController!.delegate = self
}