ViewModelFactory for Android Jetpack

ViewModelFactory.kt

class ViewModelFactory constructor(
    private val baseRepository: BaseRepository, // your repository class to handle database, network, shared preferences, etc.
    owner: SavedStateRegistryOwner,
    defaultArgs: Bundle? = null
) : AbstractSavedStateViewModelFactory(owner, defaultArgs) {

    // usage in activity:
    // val sharedVM by viewModels<MySharedViewModel> { ViewModelFactory(App.getRep(), this) }
    // App.getRep() returns instance of BaseRepository, replace with your actual logic
    
    // usage in fragment:
    // private val sharedVM: MySharedViewModel by activityViewModels()
    // private val viewModel by viewModels<ViewModelHistory> { getViewModelFactory() }

    // usage in ViewModels: 
    // class ViewModelHistory(repository: BaseRepository) : ViewModel(), VMRepository {
    // class ViewModelHistoryState(repository: BaseRepository, state: SavedStateHandle) : ViewModel(), VMRepositoryState {

    override fun <T : ViewModel> create(
        key: String,
        modelClass: Class<T>,
        handle: SavedStateHandle
    ) = with(modelClass.interfaces) {
        when {
            contains(VMRepository::class.java) ->
                modelClass
                    .getConstructor(BaseRepository::class.java)
                    .newInstance(baseRepository)
            contains(VMRepositoryState::class.java) ->
                modelClass
                    .getConstructor(BaseRepository::class.java, SavedStateHandle::class.java)
                    .newInstance(baseRepository, handle)
            else ->
                throw IllegalArgumentException("Unknown ViewModel class: ${modelClass.name}")
        }
    } as T
}

fun Fragment.getViewModelFactory(): ViewModelFactory {
    // val repository = (requireContext().applicationContext as App).getRepository()
    return ViewModelFactory(App.getRep(), this, arguments) // App.getRep() returns instance of BaseRepository, replace with your actual logic
}

interface VMRepository
interface VMRepositoryState

Unfortunately this code (reflexions) doesn't work with Proguard/R8 so you'll have to exclude viewmodels from the obfuscation using these Proguard rules:

-keepclasseswithmembers class * {
public <init>(app.acom.mypackage.BaseRepository);
}

-keepclasseswithmembers class * {
public <init>(app.acom.mypackage.BaseRepository, androidx.lifecycle.SavedStateHandle);
}

Alternative would be this code