Reloading tab bar appearance

Question

I am trying to reload the tab bar after the user changes the appearance of the app from light to dark mode and vice versa. I am able to update everything in the app except the tab bar. I don't want to force the user to close the app.

Answer 1

If you try to look at docs about UIAppearance, you'll see the note:

iOS applies appearance changes when a view enters a window, it doesn’t change the appearance of a view that’s already in a window. To change the appearance of a view that’s currently in a window, remove the view from the view hierarchy and then put it back.

Based on this note you can change appearance with a little trick by remove and immediately set back the most top view in the hierarchy after applying changes to appearance:

guard let currentView = (UIApplication.shared.delegate as? AppDelegate)?.window?.rootViewController?.view,
    let superview = currentView.superview else { return }

UITabBar.appearance().tintColor = .green

currentView.removeFromSuperview()
superview.addSubview(currentView)

Answer 2

With iOS 13 you can override traitCollectionDidChange(_:) in UITabBarController to make changes. See documentation.

Example:

class TabBarControllerViewController: UITabBarController {

    ...

    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        self.tabBar.barTintColor = UIColor.red
        self.tabBar.unselectedItemTintColor = UIColor.darkGray
        self.tabBar.tintColor = UIColor.white
  }
}