Reputation: 13803
I need to pass value when the view model is created (userData), so I need to create a view model factory
here is my viewModel, I need application
and userData
to init this ScoreViewModel
class ScoreViewModel(application: Application, userData: UserKM) : AndroidViewModel(application) {
}
but now I am confused how to pass application
when I create viewModel factory
class ScoreViewModelFactory(private val userData: UserKM) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(ScoreViewModel::class.java)) {
return ScoreViewModel(userData = userData,application = ?????? ) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
what should I do ?
Upvotes: 12
Views: 14829
Reputation: 9994
You can have something like this :
class Factory(val app: Application) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(NewsViewModel::class.java)) {
@Suppress("UNCHECKED_CAST")
return NewsViewModel(app) as T
}
throw IllegalArgumentException("Unable to construct viewmodel")
}
}
In your activity or fragment you have :
/**
* One way to delay creation of the viewModel until an appropriate lifecycle method is to use
* lazy. This requires that viewModel not be referenced before onActivityCreated, which we
* do in this Fragment.
*/
private val viewModel: NewsViewModel by lazy {
val activity = requireNotNull(this.activity) {
"You can only access the viewModel after onActivityCreated()"
}
ViewModelProviders.of(this, NewsViewModel.Factory(activity.application))
.get(NewsViewModel::class.java)
}
And here your viewModel can look like :
class NewsViewModel(application: Application) : AndroidViewModel(application)
For more detail you can look at : https://github.com/Ali-Rezaei/News-Cache/blob/master/app/src/main/java/com/sample/android/news/viewmodels/NewsViewModel.kt
Upvotes: 15