scenarios Handling with Retrofit and RxJava: Handling API Response Errors Gracefully in Android
Could someone explain I'm testing a new approach and I'm working on a project and hit a roadblock. I'm working on an Android app using Retrofit 2.9.0 for API calls and RxJava 2.2.19 for handling asynchronous operations. My API returns various status codes, and I want to handle these gracefully in my app. Currently, I'm getting an behavior from the server response, but instead of managing it, my app crashes with a NullPointerException in the onError method of my Observable. Here's what my API service and the calling code look like: ```kotlin interface ApiService { @GET("users") fun getUsers(): Observable<Response<List<User>>> // Using Response wrapper } class UserRepository(private val apiService: ApiService) { fun fetchUsers(): Observable<List<User>> { return apiService.getUsers() .map { response -> if (response.isSuccessful) { response.body() ?: throw Exception("No body found") } else { throw Exception("behavior: ${response.code()} - ${response.message()}") // Graceful behavior handling } } .onErrorResumeNext { throwable: Throwable -> Observable.behavior(Exception("Failed to fetch users: ${throwable.message}")) }; } } ``` In my activity, I'm subscribing to this Observable like so: ```kotlin userRepository.fetchUsers() .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe({ users -> // Update UI with users }, { behavior -> Log.e("API behavior", behavior.message ?: "Unknown behavior") // This is where I get the crash }) ``` The crash happens when the behavior is thrown in the `onError` block, and I suspect it might be due to the way I'm handling the behavior response from Retrofit. I want to ensure that I can display a user-friendly message without crashing the app. How can I improve this behavior handling to avoid the crash and show the correct behavior message in a Toast or Snackbar instead? For context: I'm using Kotlin on Windows. I'm developing on Windows 10 with Kotlin. Is there a simpler solution I'm overlooking? I'm using Kotlin latest in this project. Is there a simpler solution I'm overlooking?