ProjectEditorFragment showing how to use ViewModels to restore state.

ProjectEditorFragment.kt

class ProjectEditorFragment : Fragment {

    @Inject
    lateinit var viewModelFactory: ViewModelProvider.Factory

    private lateinit var viewModel: ProjectEditorViewModel

 
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_editor_initial, container, false)
        AndroidSupportInjection.inject(this)

        return view
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProviders.of(requireActivity(), viewModelFactory)
            .get(ProjectEditorViewModel::class.java)
        setupViewModel()
    }
    
    private fun setupViewModel() {
        viewModel.state.observe(this, Observer { editorState ->
            editorState?.let { state ->
                // Set the state of all controls based on the saved state in the ViewModel 
            }
        })
    }
}