在加载数据之前，在回收中心视图的中心设置进度条，在数据加载后消失

Question

因此，我正在为我的项目遵循kotlin（https://github.com/android10/Android-CleanArchitecture-Kotlin）中的这种干净的体系结构，我想在回收者视图加载数据之前添加进度条，并在数据加载后使其消失。在此示例中，进度条位于单独的工具栏中，但就我而言，我希望位于回收者视图的中心。

这是我的布局：

<androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/list_wrapper_layout"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="8dp"
        android:background="@drawable/layout_background"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="parent">

   <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/movieList_recyclerView"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_marginTop="16dp"
            app:layout_constraintBottom_toTopOf="@+id/bottom_navigation_bar"
            app:layout_constraintEnd_toEndOf="@+id/list_horizontal_guideline_end"
            app:layout_constraintStart_toStartOf="@+id/list_horizontal_guideline_start"
            app:layout_constraintTop_toBottomOf="@+id/searchView"    />

        <ProgressBar
            android:id="@+id/progressBar"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:indeterminateTint="@color/black"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

在我的课上：

class MoviesFragment : BaseFragment() {

@Inject lateinit var navigator: Navigator
@Inject lateinit var moviesAdapter: MoviesAdapter

private lateinit var moviesViewModel: MoviesViewModel

override fun layoutId() = R.layout.fragment_movies

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    appComponent.inject(this)
    moviesViewModel = viewModel(viewModelFactory) {
        observe(movies, ::renderMoviesList)
        failure(failure, ::handleFailure)
    }
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    initializeView()
    loadMoviesList()
}
private fun initializeView() {
    movieList_recyclerView.layoutManager = StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)
    movieList_recyclerView.adapter = moviesAdapter
}

private fun loadMoviesList() {
    progressBar.visible()
    movieList_recyclerView.invisibile()
    moviesViewModel.loadMovies()
}
private fun renderMoviesList(movies: List<MovieView>?) {
    moviesAdapter.collection = movies.orEmpty()
    progressBar.invisible()
    movieList_recyclerView.visible()
}
private fun handleFailure(failure: Failure?) {
    when (failure) {
        is NetworkConnection -> renderFailure(R.string.failure_network_connection)
        is ServerError -> renderFailure(R.string.failure_server_error)
        is ListNotAvailable -> renderFailure(R.string.failure_movies_list_unavailable)
    }
}
private fun renderFailure(@StringRes message: Int) {
    movieList.invisible()
    emptyView.visible()
    hideProgress()
    notifyWithAction(message, R.string.action_refresh, ::loadMoviesList)
}
}

但是进度条根本不显示。我在做什么错了？