Why does viewWillAppear not get called when an app comes back from the background?

Why does viewWillAppear not get called when an app comes back from the background? 😕

So you're building an awesome app, and you want to make sure that when the user switches back to your app from the background, you can update the view accordingly. 📱💼

But here's the problem: the viewWillAppear method, which is supposed to be called when a view is about to become visible, doesn't seem to be working when your app comes back from the background. 😱

Don't worry, you're not alone! This is a common issue that many developers face. Let's dig into the possible reasons and easy solutions. 💡💪

Possible Causes 🤔

1. The view controller is not being displayed: One possible reason is that the view controller in question is not the one currently being displayed. If you have a navigation stack or multiple view controllers, it's essential to check if the correct view controller is on top.

2. The app is entering the foreground, not just switching views: While viewWillAppear is triggered when a view is about to become visible, it is not called when the app enters the foreground. The app delegate's applicationWillEnterForeground method is called instead. This is something to keep in mind when handling the app's lifecycle.

Easy Solutions ✅

1. Check the view controller hierarchy: Verify if the correct view controller is at the top of the stack when switching back from the background. Make sure it is the one that should trigger the desired behavior in the viewWillAppear method.

2. Use the proper lifecycle method: Normally, you should avoid calling viewWillAppear directly. Instead, consider using the appropriate app delegate method called applicationWillEnterForeground. In this method, you can access the current view controller and perform the necessary updates.

Here's an example of how you can accomplish this:

func applicationWillEnterForeground(_ application: UIApplication) {
    guard let topViewController = UIApplication.shared.keyWindow?.rootViewController as? YourTopViewController else {
        return
    }
    topViewController.updateViewForForeground()
}

In the above example, we obtain the topmost view controller from the key window and cast it YourTopViewController. Then, we call the updateViewForForeground method on it to handle the necessary updates.

Call-to-Action 📣

Now you have a better understanding of why viewWillAppear may not get called when your app returns from the background. Remember to check the view controller hierarchy and consider using the appropriate app delegate method.

If you found this blog post useful, make sure to share it with your fellow developers. Also, feel free to leave a comment if you have any other related questions or tips to share. Let's help each other fix these common issues! 🤝👨‍💻

Happy coding! 💻✨