How to inject a ViewModel into BottomSheetDialogFragment with Dagger2?

Question

I inject my dependencies in Activities and Fragments on the preferred way with AndroidInjection.inject(this). I have the recommended ViewmodelFactory to inject the viewmodel. My injections are working in Activities and Fragments. However I face a problem with BottomSheetDialogFragment, because I am not allowed to specify BottomSheetDialogFragment as this. So my @Inject lateinit var viewModelFactory: ViewModelFactory is not initialized. I believe that injection should be possible because the BottomSheetDialogFragment should be subclass of the Fragment class, but it looks like it is not. I use android.x which I believe can cause also problem. Is that possible that it is not supported by Dagger yet?

What way should I implement my ViewModelFactory injection?

Update: When I try to inject a fragment with AndroidInjection.inject(this), it is not possible either with the androidx.fragment.app.Fragment only with android.app.Fragement. I extend my Fragments with DaggerFragment and they work as expected.

Answer 1

Here is how I have provided ViewModel into BottomSheetDialogFragment(). First of all set up Dagger in MyApp class.

class MyApp : Application(), HasActivityInjector, HasSupportFragmentInjector {

@Inject
lateinit var activityInjector: DispatchingAndroidInjector<Activity>
@Inject
lateinit var supportFragmentInjector: DispatchingAndroidInjector<Fragment>

override fun onCreate() {
    super.onCreate()

    initDagger()
}

override fun activityInjector(): AndroidInjector<Activity> = activityInjector

override fun supportFragmentInjector(): AndroidInjector<Fragment> = supportFragmentInjector

private fun initDagger(){
    DaggerAppComponent
        .builder()
        .application(this)
        .build()
        .injectApp(this)
}

Then AppComponent class

@Singleton
@Component(
modules = [
    AppModule::class,
    UiModule::class,
    AndroidSupportInjectionModule::class,
    AndroidInjectionModule::class
])interface AppComponent : AndroidInjector<MyApp> {

   @Component.Builder
   interface Builder {
       @BindsInstance
       fun application(application: MyApp): Builder

       fun build(): AppComponent
   }

    fun injectApp(app: MyApp)
}

Here we interested in UiModule::class

@Module
abstract class UiModule {

    @Binds
    abstract fun bindViewModelFactory(factory: ViewModelFactory): ViewModelProvider.Factory

    @PerFragment
    @ContributesAndroidInjector(modules = [(FilterModule::class)])
    abstract fun contributeFilterFragment(): FilterFragment
}

you already have ViewModelFactory , so I don't paste this code. Then FilterModule

@Module
abstract class FilterModule {

   @Binds
   @IntoMap
   @PerFragment
   @ViewModelKey(FilterViewModel::class)
   abstract fun bindViewModel(viewModel: FilterViewModel): ViewModel
}

and finally FilterFragment and FilterViewModel

class FilterFragment : BottomSheetDialogFragment() {

   @Inject
   lateinit var factory: ViewModelProvider.Factory

   private lateinit var binding: FragmentFilterBinding
   private lateinit var viewModel: FilterViewModel

   override fun onAttach(context: Context?) {
       AndroidSupportInjection.inject(this)
       super.onAttach(context)
   }

   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
       binding = getDataBinding(inflater, R.layout.fragment_filter, container)
       viewModel = getViewModel(factory)
       binding.viewModel = viewModel
       return binding.root
   }
}

class FilterViewModel @Inject constructor(private val testUseCase:TestUseCase) : BaseViewModel() {
     //do something
}

fragment_filter layout

<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:bind="http://schemas.android.com/tools">

<data>

    <variable
        name="viewModel"
        type="com.myapp.presentation.screen.filter.FilterViewModel" />
</data>
   .......

getDataBinding() and getViewModel() are extension functions

fun <T : ViewDataBinding> Fragment.getDataBinding(inflater: LayoutInflater, @LayoutRes layoutId: Int, container: ViewGroup?): T =
    DataBindingUtil.inflate(inflater, layoutId, container, false)

inline fun <reified T : BaseViewModel> Fragment.getViewModel(factory: ViewModelProvider.Factory = ViewModelProviders.DefaultFactory(activity!!.application)): T =
    ViewModelProviders.of(this, factory).get(T::class.java)