Why can i create ViewModel with instance

Question

I create ViewModel with ViewModelProvider.Factory in my fragment. Everthing work fine.

var reportViewModel = ViewModelProviders.of(this,ViewModelProvide(RemoteDataProviderImpl(
        WeakReference(context!!))))
       .get(ReportViewModel::class.java)

But after i create viewmodel directly with instance and then work everthing fine

var reportViewModel = ReportViewModel(RemoteDataProviderImpl(WeakReference(context!!)))

It is simple ViewModel

class ReportViewModel(private var provider:RemoteDataProvider) : ViewModel(){
var posts = MutableLiveData<List<Report>>()
fun getPost(){
    provider.getComments().enqueue(object : Callback<ArrayList<Report>> {
        override fun onFailure(call: Call<ArrayList<Report>>, t: Throwable) {
            t.message
        }
        override fun onResponse(
            call: Call<ArrayList<Report>>,
            response: Response<ArrayList<Report>>
        ) {
            if (response.isSuccessful){
                val reports = response.body()
                posts.value = reports
                }
            }

        })
    }
}

What is difference this two code. If i can create viewModel with directly why i need ViewModelProviders?

Answer 1

 ReportViewModel(RemoteDataProviderImpl(WeakReference(context!!)))

will

• create a new reference of the viewmodel without any scope of the activity or fragment.

• A new reference of the viewmodel will be created in onCreate of the activity. ( even if the activity is rotated or configuration is changed )

• It would not observe the scope of the activity ,i.e, it would exist even when the activity is destroyed !

While

 ViewModelProvider.of(this).get(...)

will

• Observe the scope of the activity, i.e, when the activity is finished , onCleared(..) of the viewmodel would be called ! ( Viewmodel would be destroyed )

• Same instance of the viewmodel would persist even during the configuration change.