将 LifecycleObserver 与 ViewModel 一起使用是一种好习惯吗

Question

I am using LifecycleObserver with ViewModel and it is working fine but is it a good practice to use LifecycleObserver with ViewModel ?

ViewModel.kt

class ViewModel() :ViewModel(), LifecycleObserver 
{
    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun startTimer() {

    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    fun stopTimer() {

    }
}

Fragment.kt

class Fragment : Fragment()
{
    private val viewModel: ViewModel by lazy {
        ViewModelProviders.of(this).get(ViewModel::class.java)
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?
    {
        val binding = DataBindingUtil.inflate(inflater, R.layout.fragment_people, container, false)

        viewLifecycleOwner.lifecycle.addObserver(viewModel)

        return binding.root
    }
}

Answer 1

Well, architecture component is specifically designed to place everything where everything should be, cause it follows the Separation of Concern .
-> ViewModel we don't define lifecycle inside the viewmodel, because that's what viewModel does. But if still there is a case you wanna call any lifeCycle method, ie: onDestroy , onAttach() you would still have to call them inside Activity or Fragment .
-> Repository is meant for fetching the data either to local cache or remote server, but if you skip the repository and somehow directly hop your all code inside the viewModel your code become tightly coupled and it won't no longer be flexible.
Respecting the Separation of Concern gives your code awesome flexibility.