[FIXED] share data between fragments using ModelFactory

Issue

I've successfully implemented repository based MVVM. However I need to pass a class object between fragments. I've implemented a sharedViewModel between multiple fragments but the set value always gives null. I know this is due to me not passing the activity context to the initialization of the viewmodels in fragments. I am working with ModelFactory to make instances of my viewmodel yet I can't figure out a way to give 'applicationActivity()' .

Here's my modelFactory:

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

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

and this is how I intialize my viewmodel:

  viewModel=ViewModelProvider(this, MyViewModelFactory(
        MyRepository(MyServices() ) )).get(MyOwnViewModel::class.java)

fetching data and everything else works, but I need to be able to share data between fragments and i can't do that with this architecture. I'm not using dagger or Hilt. Thank you for any pointers.

Solution

You can use by activityViewModels() and pass the factory

private val myViewModel: MyViewModel by activityViewModels(factoryProducer = {
    MyViewModelFactory(<your respository instance>)
})

It would be good idea to get your repository instance from a singleton or from a field in Application class. If you choose to get from an Application class you can do it like this;

class MyApp: Application() {

    val service by lazy { MyService() }
    val repository by lazy { MyRepository(service) }
}

by defining them lazy, it ensures that they are not initialized until its necessary

With your application class, your viewmodel call should look like this

private val myViewModel: MyViewModel by activityViewModels(factoryProducer = {
    MyViewModelFactory((activity?.application as MyApp).repository)
})

Answered By - Aslan Sarı