We have been discussing about this but we don&#39;t know the reason of creating a viewmodel factory to create a viewmodel instead of instantiate the viewmodel directly. What is the gain of creating a factory that just creates the viewmodel?

I just put a simple example of how I did it without Factory

here is the kodein module:

    val heroesRepositoryModel = Kodein {
        bind&lt;HeroesRepository&gt;() with singleton {
            HeroesRepository()
        }
    
        bind&lt;ApiDataSource&gt;() with singleton {
            DataModule.create()
        }
    
        bind&lt;MainViewModel&gt;() with provider {
            MainViewModel()
        }
    }

The piece of the Activity where I instantiate the viewmodel without using the factory 

    class MainActivity : AppCompatActivity() {
        private lateinit var heroesAdapter: HeroAdapter
        private lateinit var viewModel: MainViewModel
        private val heroesList = mutableListOf&lt;Heroes.MapHero&gt;()
        private var page = 0
        private var progressBarUpdated = false
    
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            viewModel = ViewModelProviders.of(this)
                    .get(MainViewModel::class.java)
            initAdapter()
            initObserver()
            findHeroes()
        }

The ViewModel where I instantiate the usecase directly without having it in the constructor

    class MainViewModel : ViewModel(), CoroutineScope {
    
        private val heroesRepository: HeroesRepository = heroesRepositoryModel.instance()
        val data = MutableLiveData&lt;List&lt;Heroes.MapHero&gt;&gt;()
    
        private var job: Job = Job()
        override val coroutineContext: CoroutineContext
            get() = uiContext + job
    
        fun getHeroesFromRepository(page: Int) {
            launch {
                try {
                    val response = heroesRepository.getHeroes(page).await()
                    data.value = response.data.results.map { it.convertToMapHero() }
                } catch (e: HttpException) {
                    data.value = null
                } catch (e: Throwable) {
                    data.value = null
                }
            }
        }
    
        override fun onCleared() {
            super.onCleared()
            job.cancel()
        }
    }


So here a example using factory

    class ListFragment : Fragment(), KodeinAware, ContactsAdapter.OnContactListener {
    
        override val kodein by closestKodein()
    
        private lateinit var adapterContacts: ContactsAdapter
    
        private val mainViewModelFactory: MainViewModelFactory by instance()
        private val mainViewModel: MainViewModel by lazy {
            activity?.run {
                ViewModelProviders.of(this, mainViewModelFactory)
                    .get(MainViewModel::class.java)
            } ?: throw Exception(&quot;Invalid Activity&quot;)
        }
    
        override fun onCreateView(
                inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
            return inflater.inflate(R.layout.fragment_list, container, false)
        }


The viewmodelfactory:

    class MainViewModelFactory (private val getContacts: GetContacts) : ViewModelProvider.Factory {
    
        override fun &lt;T : ViewModel?&gt; create(modelClass: Class&lt;T&gt;): T {
            if (modelClass.isAssignableFrom(MainViewModel::class.java)) {
                return MainViewModel(getContacts) as T
            }
            throw IllegalArgumentException(&quot;Unknown ViewModel class&quot;)
        }
    }

And the viewmodel:

    class MainViewModel(private val getContacts: GetContacts) : BaseViewModel() {
        lateinit var gamesList: LiveData&lt;PagedList&lt;Contact&gt;&gt;
        var contactsSelectedData: MutableLiveData&lt;List&lt;Contact&gt;&gt; = MutableLiveData()
        var contactsSelected: ArrayList&lt;Contact&gt; = ArrayList()
        private val pagedListConfig by lazy {
            PagedList.Config.Builder()
                    .setEnablePlaceholders(false)
                    .setInitialLoadSizeHint(PAGES_CONTACTS_SIZE)
                    .setPageSize(PAGES_CONTACTS_SIZE)
                    .setPrefetchDistance(PAGES_CONTACTS_SIZE*2)
                    .build()
        }

Here is the complete first example:

https://github.com/ibanarriolaIT/Marvel/tree/mvvm

And the complete second example:

https://github.com/AdrianMeizoso/Payment-App

All Kodein Solutions on Gang of Coders

Total of 1 Kodein Solutions

Why a viewmodel factory is needed in Android?