How to give same instance of ViewModel to both the Parent and Child fragment

Implement fragment-ktx in your app -> build.gradle:

implementation 'androidx.fragment:fragment-ktx:1.2.5

If you are using Navigation Component (https://developer.android.com/guide/navigation)

In the parentFragment, you can get the viewModel like this:

private val viewModel by viewModels<DemoViewModel>()

And then when you need that viewModel in the childFragment you can get it this way:

private val viewModel by viewModels<DemoViewModel>({requireGrandParentFragment()})

the requireGrandParentFragment() is a custom extension of Fragment:

fun Fragment.requireGrandParentFragment() = this.requireParentFragment().requireParentFragment()

If you are not using Navigation Component

you can access it like this:

private val viewModel by viewModels<DemoViewModel>({requireParentFragment()})

Using Fragment-ktx we can do as In **ParentFragment**

 private val viewModel: DemoViewModel by viewModels()

And

In ChildFragment

 private val viewModel: DemoViewModel by viewModels(
    ownerProducer = { requireParentFragment() }
)

Doing this we can get same instance of ViewModel in Parent Fragment and ChildFragment

add dependencies in app -> build.gralde

implementation 'androidx.fragment:fragment-ktx:1.1.0

Create your ViewModel with Activity scope. Then all Fragment within that Activity will get same ViewModel instance.

Check official ViewModelProviders reference. You can create ViewModel with both Activity and Fragment scope.

ViewModelProvider of (FragmentActivity activity)

Creates a ViewModelProvider, which retains ViewModels while a scope of given Activity is alive. More detailed explanation is in ViewModel.

and

ViewModelProvider of (Fragment fragment)

Creates a ViewModelProvider, which retains ViewModels while a scope of given fragment is alive. More detailed explanation is in ViewModel.

Sample code for creating ViewModel

From Activity:

 movieListViewModel = ViewModelProviders.of(this).get(MovieListViewModel.class);

From Fragment:

 movieListViewModel = ViewModelProviders.of(getActivity()).get(MovieListViewModel.class);

Related