CODEWITHSUNDEEP
androidandroid-jetpack-composeandroid-jetpack-navigation
Vivek Singh
Vivek Singh

Reputation: 1221

Cannot create an instance of viewmodel while using Jetpack Compose navigation

I am using navigation component for jetpack compose in my app like this:

@Composable
fun FoodiumNavigation() {
    val navController = rememberNavController()

    NavHost(
        navController = navController,
        startDestination = Screen.Main.route,
    ) {
        composable(Screen.Main.route) {
            MainScreen(navController)
        }

        ...
    }
}

And I am getting viewmodel in my MainScreen composable like this:

@Composable
fun MainScreen(navController: NavController) {
    val mainViewModel: MainViewModel = viewModel()
    ...
}

which is giving me a runtime exception as Cannot create an instance of class com.package.main.MainViewModel.

Here, I am stating that this only happens while using navigation component, i.e. everything was working fine and mainViewModel was successfully instantiated before using navigation component in my app.

The MainViewModel is like this:

@ExperimentalCoroutinesApi
@HiltViewModel
class MainViewModel @Inject constructor(private val postRepository: PostRepository) :
    ViewModel() {

    private val _postsLiveDataState = MutableLiveData<UiState<List<Post>>>()
    val postLiveState: LiveData<UiState<List<Post>>> = _postsLiveDataState

    init {
        getPostsState()
    }

    private fun getPostsState() {
        viewModelScope.launch {
            postRepository.getAllPosts()
                .onStart { _postsLiveDataState.value = UiState(loading = true) }
                .map { resource -> UiState.fromResource(resource) }
                .collect { state -> _postsLiveDataState.value = state }
        }
    }
}

Upvotes: 16

Views: 10475

Answers (4)

Ziens
Ziens

Reputation: 401

You can use viewModel() as well, but check that owning Activity or Fragment has been annotated with @AndroidEntryPoint.

Upvotes: 1

Moha.AZ
Moha.AZ

Reputation: 1903

You should add this

implementation("androidx.hilt:hilt-navigation-compose:1.0.0")

then you can use this code for create instance of your viewmodel

val viewModel: YourViewModelClass= hiltViewModel()

Upvotes: 5

Loveth
Loveth

Reputation: 431

If your @HiltViewModel is scoped to the navigation graph use hiltNavGraphViewModel() instead of viewModel() to initialize. For more reference android documentaion

Update

hiltNavGraphViewModel() is now deprecated, use hiltViewModel() instead

Thanks to Narek Hayrapetyan for the reminder

Upvotes: 22

Narek Hayrapetyan
Narek Hayrapetyan

Reputation: 1929

hiltNavGraphViewModel is deprecated, should be used hiltViewModel() instead

also add dependency androidx.hilt:hilt-navigation-compose:1.0.0-alpha03

Upvotes: 5

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