Final Results

Your todo_roster layout resource should resemble:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".ui.MainActivity">

  <ProgressBar
    android:id="@+id/loading"
    style="?android:attr/progressBarStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

  <TextView
    android:id="@+id/empty"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/msg_empty"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:visibility="gone"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

  <androidx.recyclerview.widget.RecyclerView
    android:id="@+id/items"
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

(from T27-Load/ToDo/app/src/main/res/layout/todo_roster.xml)

The modified RosterMotor should look like:

package com.commonsware.todo.ui.roster

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.commonsware.todo.repo.ToDoModel
import com.commonsware.todo.repo.ToDoRepository
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.stateIn
import kotlinx.coroutines.launch

data class RosterViewState(
  val items: List<ToDoModel> = listOf(),
  val isLoaded: Boolean = false
)

class RosterMotor(private val repo: ToDoRepository) : ViewModel() {
  val states = repo.items()
    .map { RosterViewState(it, true) }
    .stateIn(viewModelScope, SharingStarted.Eagerly, RosterViewState())

  fun save(model: ToDoModel) {
    viewModelScope.launch {
      repo.save(model)
    }
  }
}

(from T27-Load/ToDo/app/src/main/java/com/commonsware/todo/ui/roster/RosterMotor.kt)

And the tweaked RosterListFragment should look like:

package com.commonsware.todo.ui.roster

import android.os.Bundle
import android.view.*
import androidx.fragment.app.Fragment
import androidx.lifecycle.lifecycleScope
import androidx.navigation.fragment.findNavController
import androidx.recyclerview.widget.DividerItemDecoration
import androidx.recyclerview.widget.LinearLayoutManager
import com.commonsware.todo.R
import com.commonsware.todo.databinding.TodoRosterBinding
import com.commonsware.todo.repo.ToDoModel
import kotlinx.coroutines.flow.collect
import org.koin.androidx.viewmodel.ext.android.viewModel

class RosterListFragment : Fragment() {
  private val motor: RosterMotor by viewModel()
  private var binding: TodoRosterBinding? = null

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    setHasOptionsMenu(true)
  }

  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View = TodoRosterBinding.inflate(inflater, container, false)
    .also { binding = it }
    .root

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val adapter = RosterAdapter(
      layoutInflater,
      onCheckboxToggle = { motor.save(it.copy(isCompleted = !it.isCompleted)) },
      onRowClick = ::display
    )

    binding?.items?.apply {
      setAdapter(adapter)
      layoutManager = LinearLayoutManager(context)

      addItemDecoration(
        DividerItemDecoration(
          activity,
          DividerItemDecoration.VERTICAL
        )
      )
    }

    viewLifecycleOwner.lifecycleScope.launchWhenStarted {
      motor.states.collect { state ->
        adapter.submitList(state.items)

        binding?.apply {
          loading.visibility = if (state.isLoaded) View.GONE else View.VISIBLE

          when {
            state.items.isEmpty() && state.isLoaded -> {
              empty.visibility = View.VISIBLE
              empty.setText(R.string.msg_empty)
            }
            else -> empty.visibility = View.GONE
          }
        }
      }
    }
  }

  override fun onDestroyView() {
    binding = null

    super.onDestroyView()
  }

  override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
    inflater.inflate(R.menu.actions_roster, menu)

    super.onCreateOptionsMenu(menu, inflater)
  }

  override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
      R.id.add -> {
        add()
        return true
      }
    }

    return super.onOptionsItemSelected(item)
  }

  private fun display(model: ToDoModel) {
    findNavController()
      .navigate(RosterListFragmentDirections.displayModel(model.id))
  }

  private fun add() {
    findNavController().navigate(RosterListFragmentDirections.createModel(null))
  }
}

(from T27-Load/ToDo/app/src/main/java/com/commonsware/todo/ui/roster/RosterListFragment.kt)

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