CODEWITHSUNDEEP
androidandroid-jetpackandroid-navigationandroid-architecture-navigationkoin
rubin94
rubin94

Reputation: 532

Pass data back to previous fragment using Android Navigation

I've started using Android Architecture Components (Navigation and Safe Args, View Models) along with Koin library.

Currently, I've got a problem with passing arguments between two fragments - I need to pass a string value from fragment A to fragment B, modify this value in fragment B and pass it back to fragment A.

I've found one possible solution to my problem - shared view models. Unfortunately, this approach has one problem because I can pass and modify values between screens, but when the fragment A navigate to another destination the value in the shared view model is still stored and not cleared.

Is there any different solution of passing and modifying data between fragments in Android Navigation? I want to avoid clearing this one value by hand (when the fragment A is destroyed).

Upvotes: 48

Views: 30329

Answers (5)

zgluis
zgluis

Reputation: 3340

Android just released a solution for this; Passing data between Destinations (Navigation 2.3.0-alpha02), basically, in fragment A you observe changes in a variable and in fragment B you change that value before executing popBackStack().

Fragment A:

findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<String>("key")?.observe(viewLifecycleOwner) { result ->
    // Do something with the result.
}

Fragment B:

navController.previousBackStackEntry?.savedStateHandle?.set("key", result)
navController.popBackStack()

Upvotes: 75

furkanbzkurt
furkanbzkurt

Reputation: 356

You can use Fragment Result API.

Fragment A -> Fragment B

In Fragment A :

binding.buttonGo.setOnClickListener {
   setFragmentResultListener(ADD_LOCATION) { key, bundle ->
       clearFragmentResultListener(requestKey = ADD_LOCATION)
       val selectedLocationModel =
           bundle.getParcelable<LocationModel>(SELECTED_LOCATION_MODEL)
       this.selectedLocationModel = selectedLocationModel
   }
   navToFragmentB()
}

In Fragment B:

setFragmentResult(
    ADD_LOCATION,
    bundleOf(SELECTED_LOCATION_MODEL to selectedLocationModel)
)
goBack()

Do not forget to call clearFragmentResultListener() before create new one.

Upvotes: 3

Artem Motuzniy
Artem Motuzniy

Reputation: 1

You can try this solution

<fragment
    android:id="@+id/a"
    android:name="...">

    <argument
        android:name="text"
        app:argType="string" />

    <action
        android:id="@+id/navigate_to_b"
        app:destination="@id/b" />

</fragment>

<fragment
    android:id="@+id/b"
    android:name="...">

    <argument
        android:name="text"
        app:argType="string" />

    <action
        android:id="@+id/return_to_a_with_arguments"
        app:destination="@id/a"
        app:launchSingleTop="true"
        app:popUpTo="@id/b"
        app:popUpToInclusive="true" />

</fragment>

and navigation fragment

NavHostFragment.findNavController(this).navigate(BFragmentDirections.returnToAWithArguments(text))

ianhanniballake`s comment has helped me solve a similar problem

Upvotes: 0

EpicPandaForce
EpicPandaForce

Reputation: 81529

Currently, I've got a problem with passing arguments between two fragments - I need to pass a string value from fragment A to fragment B, modify this value in fragment B and pass it back to fragment A.

The theoretical solution really is to have the two fragments in a shared <navigation tag, then scope the ViewModel to the ID of the navigation tag, this way you now share the ViewModel between the two screens.

To make this reliable, it's best to use the NavBackStackEntry of the Navigation tag as both a ViewModelStoreOwner and SavedStateRegistryOwner, and create an AbstractSavedStateViewModelFactory that will create the ViewModel using the ViewModelProvider, while also giving you a SavedStateHandle.

You can communicate the results from FragmentB to FragmentA using this SavedStateHandle, associated with the shared ViewModel (scoped to the shared NavGraph).

Upvotes: 1

Klaudia
Klaudia

Reputation: 7

1) Pass string from Fragment A to Fragment B with action_A_to_B and SafeArgs.

2) popBackStack to remove Fragment B. 

navController.popBackStack(R.id.AFragment, false);

or

navController.popBackStack();

3) Then pass modified data from B to A with action_B_to_A.

EDIT.

Here you have some another solution

Upvotes: -7

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