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@Atwa
Last active September 24, 2023 14:43
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package com.atwa.navigation
import androidx.annotation.IdRes
import androidx.annotation.MainThread
import androidx.fragment.app.Fragment
import androidx.hilt.navigation.HiltViewModelFactory
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelLazy
import androidx.navigation.fragment.findNavController
/**
* The viewModel must be created in the owner fragment for the first time using hiltNavGraphViewModels as following :
```
private val mViewModel by hiltNavGraphViewModels<SomeViewModel>(R.id.someDestination)
```
The same instance of the viewModel can then be retrieved in any other later fragment using backStackViewModels as following:
```
private val mViewModel by backStackViewModels<SomeViewModel>(R.id.someDestination)
```
Note :
- Destination can be either a nav graph's id or a destination's id for any fragment in any nav graph.
- Destination must be same in both fragments to retrieve the same instance of the cached viewModel.
- In case the destination doesn't exist in the later fragment's back stack then null would be returned.
* **/
@MainThread
public inline fun <reified VM : ViewModel> Fragment.backStackViewModels(
@IdRes destinationId: Int
): Lazy<VM?> = lazy {
findNavController().currentBackStack.value.lastOrNull { it.destination.id == destinationId }
?.let { backStackEntry ->
ViewModelLazy(
VM::class,
{ backStackEntry.viewModelStore },
{ HiltViewModelFactory(requireActivity(), backStackEntry) },
{ defaultViewModelCreationExtras }
).value
} ?: run { null }
}
@Atwa
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Atwa commented Sep 21, 2023

The viewModel must be created in the owner fragment for the first time using hiltNavGraphViewModels as following :

private val mViewModel by hiltNavGraphViewModels<SomeViewModel>(R.id.someDestination)

The same instance of the viewModel can then be retrieved in any other later fragment using backStackViewModels as following:

private val mViewModel by backStackViewModels<SomeViewModel>(R.id.someDestination)

Note :

  • Destination can be either a nav graph's id or a destination's id for any fragment in any nav graph.
  • Destination must be same in both fragments to retrieve the same instance of the cached viewModel.
  • In case the destination doesn't exist in the later fragment's back stack then null would be returned.

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