以下の記述ですが、

private val viewModel: MainViewModel by lazy {
  ViewModelProviders.of(this).get<MainViewModel>()
}

Activityで にしろ、Fragmentで にしろ、

private val viewModel: MainViewModel by viewModels()

でいける。

Fragment内で呼び出す場合は、

dependencies {
  implementation 'androidx.fragment:fragment-ktx:1.1.0-alpha08'
}

で、今現在。

コードをみてみる。

@MainThread
inline fun <reified VM : ViewModel> Fragment.viewModels(
    noinline ownerProducer: () -> ViewModelStoreOwner = { this },
    noinline factoryProducer: (() -> Factory)? = null
) = createViewModelLazy(VM::class, { ownerProducer().viewModelStore }, factoryProducer)

@MainThread
inline fun <reified VM : ViewModel> Fragment.activityViewModels(
    noinline factoryProducer: (() -> Factory)? = null
) = createViewModelLazy(VM::class, { requireActivity().viewModelStore }, factoryProducer)

@MainThread
fun <VM : ViewModel> Fragment.createViewModelLazy(
    viewModelClass: KClass<VM>,
    storeProducer: () -> ViewModelStore,
    factoryProducer: (() -> Factory)? = null
): Lazy<VM> {
    val factoryPromise = factoryProducer ?: {
        val application = activity?.application ?: throw IllegalStateException(
            "ViewModel can be accessed only when Fragment is attached"
        )
        AndroidViewModelFactory.getInstance(application)
    }
    return ViewModelLazy(viewModelClass, storeProducer, factoryPromise)
}

使ったほうが良いですよね。

はまらなくてすむ。

👉【MVVM】 ViewModel の_プロパティ記述

androidx.fragment.app  |  Android Developers

関連ワード:  Android・AndroidStudio・おすすめ・開発・architecture components