大标题，居中对齐

Question

I try to center the title in large title mode, but that code doesn't affect. In AppDelegate:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center
    UINavigationBar.appearance().largeTitleTextAttributes = [NSAttributedStringKey.paragraphStyle: paragraphStyle]

    return true
}

Answer 1

The large title cannot be centered, it has it´s position to the left and is left aligned. The size of the title does not matter, if you want the title centred you have to create your own custom one.

Answer 2

I solved this by making the navigationItem title to none. Then setting a custom label with my text and adding constraints to the label programmatically. Here is the code below.

override func setupNavigationBar() {
        navigationItem.title = .none

        if #available(iOS 11.0, *) {
            navigationController?.navigationBar.prefersLargeTitles = true

            let titleLabel = UILabel()
            titleLabel.text = "Home"
            titleLabel.translatesAutoresizingMaskIntoConstraints = false

            let targetView = self.navigationController?.navigationBar
            targetView?.addSubview(titleLabel)
            titleLabel.anchor(top: nil, left: nil, bottom: targetView?.bottomAnchor, right: nil, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 222, height: 40)

            titleLabel.centerXAnchor.constraint(equalTo: (targetView?.centerXAnchor)!).isActive = true

        } else {
            // Fallback on earlier versions
        }

    }

Answer 3

UINavigationBar automatically centers its titleView as long as there is enough room. I suppose your code won't affect actual titleView frame because you don't have back button or rightBarButton, so UINavigationBar automatically prolong titleView to the right.

To fix it you can add empty right bar button, or add custom titleView with predefined frame