更改导航栏“prefersLargeTitles”时的平滑过渡

Question

I have a view controller that is pushed onto a navigation stack. The stack has navigationBar.prefersLargeTitles = true , whilst this new view controller has navigationBar.prefersLargeTitles = false . I achieve this using the following code in the view controller that is pushed onto the stack:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    navigationController?.navigationBar.prefersLargeTitles = false
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    navigationController?.navigationBar.prefersLargeTitles = true
}

However, when I return back to the presenting view controller, the change in the navigation bar from navigationBar.prefersLargeTitles = false to navigationBar.prefersLargeTitles = true is a bit glitchy. Is there any way to make this smoother?

Many thanks

Answer 1

Instead of directly changing the preference via the navigation controller, you should change the behavior via the navigation item of the specific view controller you would like to affect.

// Root UIViewController
class ViewControllerA: UIViewController {

    override func viewDidLoad() {

        super.viewDidLoad()

        navigationController?.navigationBar.prefersLargeTitles = true
        navigationItem.largeTitleDisplayMode = .always
    }
}

// Pushed UIViewController
class ViewControllerB: UIViewController {

    override func viewDidLoad() {

        super.viewDidLoad()

        navigationItem.largeTitleDisplayMode = .never
    }
}

You can remove the lines you have in viewWillAppear and viewWillDisappear .