Why a viewmodel factory is needed in Android?

Question

We have been discussing about this but we don\'t know the reason of creating a viewmodel factory to create a viewmodel instead of instantiate the viewmodel directly. What is

Answer 1

In short,

if we need to pass some input data to the constructor of the viewModel , we need to create a factory class for viewModel.

Like example :-

class MyViewModelFactory constructor(private val repository: DataRepository): ViewModelProvider.Factory {

     override fun  create(modelClass: Class): T {
        return if (modelClass.isAssignableFrom(MyViewModel::class.java!!)) {
            MyViewModel(this.repository) as T
        } else {
            throw IllegalArgumentException("ViewModel Not Found")
        }
    }
}

Reason

We cannot directly create the object of the ViewModel as it would not be aware of the lifecyclerOwner. So we use :-

ViewModelProviders.of(this, MyViewModelFactory(repository)).get(MyViewModel::class.java)