android - What are differences creating viewmodels way?

Question

I'm using viewModel in my project already. But ? know ? can initalize viewmodel with many ways. Do you know what are the differences between these ways?

• viewModel = ViewModelProvider(this).get(ViewModelClass::class.java)
• viewModel = ViewModelClass()
• viewModel : ViewModelClass : by viewModels()
• viewModel : ViewModelClass by ViewModelse{ ViewModelFactory(this,Reposityory(),intent }

What are the technical differences?

question from:https://stackoverflow.com/questions/65649963/what-are-differences-creating-viewmodels-way

Answer 1

By using

• viewModel = ViewModelProvider(this).get(ViewModelClass::class.java) your are creating an instance of ViewModelClass scoped to this Fragment/activity and whenever the activity gets recreated same instance of the viewmodel is assigned rather than a new instance

• viewModel = ViewModelClass() though it seems to be correct, it isn't . Whenever the activity gets recreated, new instance of viewmodel is assigned. Dont try to create an instance of ViewModel by directly calling its constructor, instead let the ViewModelProvider do the job.

• viewModel: ViewModelClass by viewModels() courtesy of Android KTX here you delegate the creation of ViewModel . Its similar to

  val viewModel by lazy{
     ViewModelProvider(this).get(MyViewModel::class.java)
  }

• viewModel : ViewModelClass by ViewModels{ ViewModelFactory(this,Reposityory(),intent)} its similar to

val viewModel by lazy {
    ViewModelProvider(this, ViewModelFactory(this,Reposityory(),intent)).get(MyViewModel::class.java)
}