Gist for Medium version of https://ajkueterman.dev/posts/android-viewmodel-manual-dependency-injection-made-easy/

01.kt

class MyActivity : AppCompatActivity() {

    private val model: MyViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        model.getUsers().observe(this, Observer<List<User>>{ users ->
            // update UI
        })
    }
}

02.kt

fun createWithFactory(
  create: () -> ViewModel
  ): ViewModelProvider.Factory {
    return object : ViewModelProvider.Factory {
        override fun <T : ViewModel?> create(modelClass: Class<T>): T {
            @Suppress("UNCHECKED_CAST")// Casting T as ViewModel
            return create.invoke() as T
        }
    }
}

03.kt

private val model: MyViewModel by lazy {
  ViewModelProvider(
    this, 
    createWithFactory {
        MyViewModel(repo = MyRepository())
    }
  ).get(MyViewModel::class.java)
}

04.kt

private val model: MyViewModel by activityViewModels {
    createWithFactory {
        MyViewModel(repo = MyRepository())
    }
}

05.kt

/**
 * Get a [ViewModel] in an [ComponentActivity].
 */
@MainThread
inline fun <reified VM : ViewModel> ComponentActivity.viewModelBuilder(
    noinline viewModelInitializer: () -> VM
): Lazy<VM> {
    return ViewModelLazy(
        viewModelClass = VM::class,
        storeProducer = { viewModelStore },
        factoryProducer = {
            return@ViewModelLazy object : ViewModelProvider.Factory {
                override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                    @Suppress("UNCHECKED_CAST")// Casting T as ViewModel
                    return viewModelInitializer.invoke() as T
                }
            }
        }
    )
}

/**
 * Get a [ViewModel] in a [Fragment].
 */
@MainThread
inline fun <reified VM : ViewModel> Fragment.activityViewModelBuilder(
    noinline viewModelInitializer: () -> VM
): Lazy<VM> {
    return ViewModelLazy(
        viewModelClass = VM::class,
        storeProducer = { requireActivity().viewModelStore },
        factoryProducer = {
            object : ViewModelProvider.Factory {
                override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                    @Suppress("UNCHECKED_CAST")// Casting T as ViewModel
                    return viewModelInitializer.invoke() as T
                }
            }
        }
    )
}

06.kt

private val model: MyViewModel by viewModelBuilder {
    MyViewModel(repo = MyRepository())  
}

07.kt

private val model: MyViewModel by activityViewModelBuilder {
    MyViewModel(repo = MyRepository())  
}

dependencies.groovy

dependencies { 
    implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0"
}