Smooth transition when changing navigation bar "prefersLargeTitles"

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

score 16 · Accepted Answer · edited Sep 07 '20 at 17:37

16

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.

edited Sep 07 '20 at 17:37

mkll

2,058
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answered Sep 16 '18 at 23:13

Callam

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Nice thanks, this works. As `ViewControllerA` pushes `ViewControllerB`, the navigation bar shrinks in size and moves up vertically; it reveals the black "base" screen. Is it possible to change this black colour? Thanks – ajrlewis Sep 17 '18 at 08:07
@Callam In ViewControllerA I think you want `navigationController?.navigationBar.prefersLargeTitles = true` instead of `navigationItem.largeTitleDisplayMode = .always` According to the documentation for largeTitleDisplayMode: _"If the prefersLargeTitles property of the navigation bar is false, this property has no effect and the navigation item's title is always displayed as a small title."_ When setting `prefersLargeTitles = true` it isn't necessary to also set `largeTitleDisplayMode = .always` in this case - just tried this now. – Scott Carter Jul 06 '20 at 15:34

Smooth transition when changing navigation bar "prefersLargeTitles"

1 Answers1