Updating the UINavigationBar UIAppearance in iOS Navigation Controllers

iOS provides a robust framework for building user interfaces, including navigation controllers that facilitate smooth transitions between views. One common challenge developers face is updating the UINavigationBar’s appearance when switching between different navigation controllers or view controllers.

In this article, we will delve into the specifics of navigating iOS views and how to update the UINavigationBar’s appearance in a consistent manner.

Introduction

The UINavigationBar serves as a visual indicator of the current navigation state within an app. Its appearance can be customized using various properties, such as the background color, title text color, and font style. However, when using UINavigationController, these changes are not reflected immediately after navigating away from or toward a view controller.

This issue arises because the UINavigationBar is managed by the UINavigationController instance. When a view controller is pushed onto the navigation stack, a new UINavigationBar is created and placed atop the current view. Conversely, when a view controller is popped, its associated UINavigationBar is removed.

However, there is a common misconception that updating the UINavigationBar’s appearance directly on the view controller being pushed or popped will cause the changes to be reflected in the navigation bar’s UIAppearance. Unfortunately, this is not the case.

The Issue with UIAppearance

The UIAppearance property of a UINavigationBar instance allows developers to customize its appearance without modifying the underlying implementation. However, when using UINavigationController, these customizations are not propagated through the navigation stack.

This behavior can be observed in the following code snippet:

// Assuming this is the initial view controller
let initialVC = MyInitialViewController()
let navController = UINavigationController(rootViewController: initialVC)
navController.pushViewController(MyNextVC(), animated: true)

// And here's where we update the UIAppearance
navController.topViewController?.navigationBar.UIAppearance = CustomNavigationBarAppearance()

Even though we have set the UIAppearance property, changing it will not be reflected in the navigation bar’s appearance.

The Solution

So, what’s the solution to this problem? It turns out that there is a simple yet elegant way to update the UINavigationBar’s appearance when switching between different navigation controllers or view controllers.

The key lies in modifying the view hierarchy of the window. Specifically, we need to remove all existing subviews of the navigation bar and then re-add them after updating their appearance.

Here’s an example implementation:

// In a utility class or a category of UIViewController
extension UIViewController {
    func updateNavigationBarAppearance() {
        let windows = UIApplication.shared.windows
        for window in windows {
            for view in window.subviews {
                if view.isKindOfClass(UIApplication.shared.keyWindow?.rootViewController?.navigationBar) {
                    view.removeFromSuperview()
                }
            }
            window.addSubview(self.navigationController!.topViewController?.navigationBar)
        }
    }
}

In this implementation, we iterate over all windows and their subviews. If a view is an instance of the navigation bar associated with the current view controller’s navigation stack, we remove it from its superview.

Next, we add a new instance of the UINavigationBar to each window, passing in the top view controller’s navigation bar as its superview. This ensures that the updated appearance is properly propagated through the navigation stack.

Example Use Cases

Here are some example use cases for this solution:

// Pushing a new view controller and updating its appearance
let nextVC = MyNextViewController()
nextVC.updateNavigationBarAppearance()

// Popping a pushed view controller and updating its appearance
let poppedVC = self.navigationController?.topViewController
poppedVC?.updateNavigationBarAppearance()

// Updating the navigation bar's appearance when switching between navigation controllers
class NavigationBarController: UINavigationController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let initialVC = MyInitialViewController()
        pushViewController(initialVC, animated: true)
    }

    override func popViewController(animated: Bool) {
        super.popViewController(animated)
        topViewController?.updateNavigationBarAppearance()
    }
}

In conclusion, updating the UINavigationBar’s appearance when switching between different navigation controllers or view controllers can be a challenging task. However, by leveraging the power of the view hierarchy and modifying it accordingly, we can achieve consistent and visually appealing results.

By applying this solution to your own projects, you’ll be able to provide a better user experience for your users, even in complex scenarios involving multiple views and navigation controllers.

Conclusion

The world of iOS development is filled with intricacies and challenges. By understanding the intricacies of the navigation stack and how to update the UINavigationBar’s appearance, we can create more intuitive and visually appealing interfaces for our users.

We’ve explored the complexities of updating the UINavigationBar’s appearance when switching between different views controllers or navigation controllers. We’ve also discussed potential workarounds, including modifying the view hierarchy to propagate changes through the navigation stack.

By following these guidelines and best practices, you’ll be better equipped to tackle even the most complex development challenges that come your way.

Understanding iOS Navigation Controllers and Updating the UINavigationBar UIAppearance

Introduction

The Issue with UIAppearance

The Solution

Example Use Cases

Conclusion

Further Reading