注销按钮操作不起作用

Question

上下文是，当用户点击登录按钮时，应用程序将使用 Web 服务检查凭据，如果用户被授权，则用户名和密码存储在 userDefaults 中（当用户再次打开应用程序时自动登录）

现在我在下一页使用注销按钮（用户在成功登录后进入的位置），这是我的注销按钮的代码，它不起作用。

据我说，点击注销时，它应该删除 userDefaults，然后返回登录页面。 目前我不关心外观，只是帮我写代码。

添加按钮的功能。

 override func viewDidLoad()
        {
            super.viewDidLoad()
            let doneItem = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.trash, target: nil, action: #selector(self.logoutButtonTapped(_:)));
            navigationItem.rightBarButtonItem = doneItem;
            // Do any additional setup after loading the view.
        }

注销按钮功能：

func logoutButtonTapped(_ sender: Any)
    {
        let defaults = UserDefaults.standard
        defaults.removeObject(forKey: "userName")
        defaults.removeObject(forKey: "userPassword")
        let newViewObject = storyboard?.instantiateViewController(withIdentifier: "LoginPageViewController") as! LoginPageViewController //LoginPageViewController is my login view file, and identifier also has the same name.
        navigationController?.pushViewController(newViewObject, animated: true)
    }

这是我的故事板。我正在以编程方式添加按钮。

Answer 1

如果你的 Login VC 作为初始 VC，那么在这个地方调用

let newViewObject = storyboard?.instantiateViewController(withIdentifier: "LoginPageViewController") as! LoginPageViewController //LoginPageViewController is my login view file, and identifier also has the same name.
    navigationController?.pushViewController(newViewObject, animated: true)

使用

_ = navigationController?.popViewController(animated: true)

否则

  _ = navigationController?.popToRootViewController(animated: true)

更新答案

 func logoutButtonTapped(_ sender: Any)
    {
        let defaults = UserDefaults.standard
        defaults.removeObject(forKey: "userName")
        defaults.removeObject(forKey: "userPassword")
         _ = navigationController?.popToRootViewController(animated: true)

    }

例如

  navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Logout", style: .plain, target: self, action: #selector(logoutButtonTapped))

然后像这样调用动作

 func logoutButtonTapped() {

    let defaults = UserDefaults.standard
    defaults.removeObject(forKey: "userName")
    defaults.removeObject(forKey: "userPassword")

   // _ = navigationController?.popViewController(animated: true)

     _ = navigationController?.popToRootViewController(animated: true)



}