Hilt 不会注入 Scoped ViewModel

Question

I'm trying to inject a dependency into a navigation graph scoped ViewModel

This is my app:

@HiltAndroidApp
class App : Application() 

The activity hosting my fragment:

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        findNavController(R.id.nav_host_fragment).navigate(R.id.main_graph)
    }
}

My navigation graph:

<?xml version="1.0" encoding="utf-8"?>
<navigation 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_graph"
    app:startDestination="@id/mainFragment">

    <fragment
        android:id="@+id/mainFragment"
        android:name="com.example.hilt.MainFragment" />

</navigation>

The object I'm going to inject into my ViewModel:

class Repo @Inject constructor()

My ViewModel:

@HiltViewModel
class MainViewModel @Inject constructor(
        val repo: Repo,
        application: Application
) : AndroidViewModel(application) {
    fun test(){}
}

The fragment into which I inject the view model:

@AndroidEntryPoint
class MainFragment : Fragment() {

    val viewModel: MainViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        viewModel.test()
    }
}

Now at this point everything is working properly, but as soon as I try to scope the VM using this:

@AndroidEntryPoint
class MainFragment : Fragment() {

    val viewModel: MainViewModel by navGraphViewModels(R.id.main_graph)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        viewModel.test()
    }
}

The app fails to create my ViewModel and crashes leaving this stacktrace:

 Caused by: java.lang.RuntimeException: Cannot create an instance of class com.example.hilt.MainViewModel
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:269)
        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:112)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:54)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:41)
        at com.example.hilt.MainFragment.getViewModel(Unknown Source:2)
        at com.example.hilt.MainFragment.onCreate(MainFragment.kt:17)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:2936)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:472)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2177)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2094)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1990)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3122)
        at androidx.fragment.app.FragmentManager.dispatchCreate(FragmentManager.java:3045)
        at androidx.fragment.app.Fragment.onCreate(Fragment.java:1867)
        at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:264)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:2936)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:472)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
        at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:141)
        at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
        at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:313)
        at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:292)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:780)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:696)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:170)

Clearly the by navGraphViewModels shorthand is not using the right VM Factory and I'm a bit at a loss here.

Answer 1

Use hiltNavGraphViewModels from androidx.hilt:hilt-navigation-fragment instead of navGraphViewModels

https://developer.android.com/training/dependency-injection/hilt-jetpack#viewmodel-navigation