SavedStateViewModelFactory constructed with empty constructor

Question

After updating navigation component and lifecycle viewmodel version to 2.5.0-alpha01 I have got following issue.

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.atcc.aewp/com.atcc.aewp.activity.SplashActivity}: java.lang.UnsupportedOperationException: SavedStateViewModelFactory constructed with empty constructor supports only calls to create(modelClass: Class, extras: CreationExtras).

Exception throws when view model is loaded

open class BaseActivity : AppCompatActivity() {

    private val appLanguageViewModel: AppLanguageViewModel by viewModels()

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

        appLanguageViewModel.result.observe(this) {
            ...
        }
    }
}

Here is my view model class

class AppLanguageViewModel : ViewModel() {

    private val languageLiveData = MutableLiveData<Event<ApplicationLanguage>>()

    val result: LiveData<Event<ApplicationLanguage>> = languageLiveData

    fun setLanguage(applicationLanguage: ApplicationLanguage) {
        if (LanguagePreferences.instance().setLanguage(applicationLanguage.name)) {
            languageLiveData.postValue(Event(applicationLanguage))
        }
    }
}

Sinan Kozak · Accepted Answer · 2022-12-24T10:16:38.167

10

Workaround;

    private val viewModel: AppLanguageViewModel by viewModels {
      SavedStateViewModelFactory(application, this)
    }

Reason;

Because not everything uses the new API of ViewModelFactory. The default factory in ComponentActivity is SavedStateViewModelFactory without any constructor parameter.

We have an issue with HiltViewModelFactory. It calls create method without passing new CreationExtras values. I assume this should be fixed in hilt in our case. If you can share the rest of the stack trace, we might find out the root cause in your case too.

edited Dec 24 '22 at 10:16

answered Feb 01 '22 at 12:53

Sinan Kozak

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thanks, i got this too, from fragment the code looks ugly to get the application from getting the activity first , requireactivity().application. I hope Hilt would fix this. – Jeffrey Liu Feb 13 '22 at 18:35
In my case, just using the default lamba and using `viewModels()` worked. Thanks! – Damercy Mar 14 '22 at 06:11

score 3 · Answer 2 · answered Feb 25 '22 at 08:50

In our case Sinan Kozak work around did not work. The current issues we were facing where because we were using the following versions of navigation and lifecycle

lifecycle

implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.1'
implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.4.1'

navigation

implementation 'androidx.navigation:navigation-fragment-ktx:2.5.0-alpha01'
implementation 'androidx.navigation:navigation-ui-ktx:2.5.0-alpha01'

This resulted in Biometrics on the phone not working. So, the solution our end was to revert to the previous stable release of the navigation dependencies

implementation 'androidx.navigation:navigation-fragment-ktx:2.4.1'
implementation 'androidx.navigation:navigation-ui-ktx:2.4.1'

I guess the best rule of thumb is do not use alpha build dependencies in production

SavedStateViewModelFactory constructed with empty constructor

2 Answers2