👀 Views: 1816 💬 Answers: 1 📅 Created: 2025-06-20

android viewmodel sharedpreferences kotlin

I'm maintaining legacy code that I'm dealing with I'm having trouble with I've been banging my head against this for hours....... I'm encountering a `NullPointerException` when trying to access `SharedPreferences` from my `ViewModel`. I've set up my `ViewModel` to retrieve a value from `SharedPreferences`, but occasionally, it throws an exception. The error message indicates that the `SharedPreferences` instance is null, even though I've initialized it in the `Application` class. My code looks like this: ```kotlin class MyApplication : Application() { lateinit var preferences: SharedPreferences override fun onCreate() { super.onCreate() preferences = PreferenceManager.getDefaultSharedPreferences(this) } } ``` In my `ViewModel`, I access the `SharedPreferences` like this: ```kotlin class MyViewModel(application: Application) : AndroidViewModel(application) { private val sharedPreferences = (application as MyApplication).preferences fun getSomeValue(): String? { return sharedPreferences.getString("some_key", null) } } ``` However, in some situations, especially after a configuration change, it throws `java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.SharedPreferences.getString' on a null object reference`. I have tried checking the initialization of `SharedPreferences`, and it seems to be configured correctly in the `onCreate` method of my `Application`. I've also ensured that I'm not calling `getSomeValue()` before the `Application` class is fully initialized. Additionally, I verified that the `ViewModel` is being instantiated correctly with the application context. Any ideas on why this might be happening, or how to prevent the `NullPointerException`? Am I missing something in the lifecycle management or `ViewModel` instantiation? For context: I'm using Kotlin on Ubuntu. Has anyone else encountered this? Am I missing something obvious? Thanks for any help you can provide! This is my first time working with Kotlin latest. I'm developing on Linux with Kotlin. Thanks in advance! Any examples would be super helpful.