Hi! I’m running into the following exception when executing `hiltNavGraphViewModel()` in a NavHost:...

# compose

[Walter Berggren]

Hi! I’m running into the following exception when executing hiltNavGraphViewModel() in a NavHost: Expected an activity context for creating a HiltViewModelFactory for a NavBackStackEntry but instead found: android.app.ContextImpl@78d1695

[Walter Berggren]

The culprit is overriding the locale in the main activity to be able to switch languages on the fly.

My main activity’s setContent looks like this:

setContent {
    OverrideLocale(language.value, this) {
        Navigation()
    }
}

With OverrideLocale defined as following:

@Composable
private fun OverrideLocale(language: String, mainActivity: AppCompatActivity, content: @Composable () -> Unit) {
    val configuration = LocalConfiguration.current
    configuration.setLocale(Locale(language))
    val context = LocalContext.current.createConfigurationContext(configuration)
    CompositionLocalProvider(
        LocalOnBackPressedDispatcherOwner provides mainActivity,
        LocalConfiguration provides configuration,
        LocalContext provides context
    ) {
        content()
    }
}

[Walter Berggren]

Looking at the exception’s stack trace the HiltViewModelFactory never seems to reach a point where it deems the context to be an activity:

@JvmName("create")
public fun HiltViewModelFactory(
    context: Context,
    navBackStackEntry: NavBackStackEntry
): ViewModelProvider.Factory {
    val activity = context.let {
        var ctx = it
        while (ctx is ContextWrapper) {
            if (ctx is Activity) {
                return@let ctx
            }
            ctx = ctx.baseContext
        }
        throw IllegalStateException(
            "Expected an activity context for creating a HiltViewModelFactory for a " +
                "NavBackStackEntry but instead found: $ctx"
        )
    }
[...]

[Walter Berggren]

I.e., return@let ctx above is never called.

[Walter Berggren]

Any thoughts on how the locale can be overridden correctly? Removing OverrideLocale makes the code run just fine.

[FunkyMuse]

Did you add
@AndroidEntryPoint to the activity hosting the composables?

[Albert Chang]

See this thread.

[Walter Berggren]

@FunkyMuse Yes, I’ve added @AndroidEntryPoint

[Walter Berggren]

@Albert Chang From what I can tell my implementation is pretty much identical to the one in the linked thread. That’s where I got my solution from, after all :)

[Walter Berggren]

Alright, looks like I found a solution. Instead of providing the context created by createConfigurationContext directly, I use ContextWrapper to update the getResources call to use the next context but use the MainActivity for all other calls:

class ContextWithUpdatedResources(
    private val resources: Context,
    base: Context
) : ContextWrapper(base) {
    override fun getResources(): Resources {
        return resources.resources
    }
}

My OverrideLocale is defined as following:

@Composable
private fun OverrideLocale(language: String, mainActivity: MainActivity, content: @Composable () -> Unit) {
    val configuration = LocalConfiguration.current
    configuration.setLocale(Locale(language))
    val resources = LocalContext.current.createConfigurationContext(configuration)
    CompositionLocalProvider(
        LocalOnBackPressedDispatcherOwner provides mainActivity,
        LocalConfiguration provides configuration,
        LocalContext provides ContextWithUpdatedResources(resources, mainActivity)
    ) {
        content()
    }
}

[Ian Lake]

Note that LocalOnBackPressedDispatcher also does the same context unwrapping, so overriding it isn't necessary

[Walter Berggren]

Thank you for the pointers! @Ian Lake @Albert Chang @FunkyMuse