Pass data back to previous fragment using Android Navigation

Question

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).

looking solution for a similar scenario. Is it solved, pls update? — Faisal
– Faisal, Commented Oct 30, 2019 at 11:34
See stackoverflow.com/questions/50754523/…. Basically, share a ViewModel. — Graham Perks
– Graham Perks, Commented Dec 3, 2019 at 21:34
Check out the answer here. They have just recently added the functionality to the Navigation library. — LeHaine
– LeHaine, Commented Mar 31, 2020 at 10:45

Johann · Accepted Answer · 2022-11-20 15:29:45Z

77

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()

edited Nov 20, 2022 at 15:29

Johann

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answered Apr 15, 2020 at 21:34

zgluis

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7 Comments

Zeeshan Over a year ago

Thanks! It works but this is very weird solution as compared to when you are passing data from Fragment A to Fragment B. This solution is more like old way of passing data using bundle as we are used used to do in Java.

Richa Over a year ago

can we pass multiple data using this?

VVB Over a year ago

Good job!!! Keep it up

t3ddys Over a year ago

Note: SavedStateHandle which Hilt injects into ViewModel and NavBackStackEntry SavedStateHandle are not the same objects. I spent several hours figuring this out

UnreachableCode Over a year ago

I needed a way to have an onBackPressed event in the Viewmodel. I searched for many many hours. This is the way.

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furkanbzkurt · Accepted Answer · 2022-03-07 17:23:33Z

3

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.

edited Mar 7, 2022 at 17:23

answered Mar 7, 2022 at 15:13

furkanbzkurt

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1 Comment

Noorul Over a year ago

This one is very fine Answer. Thanks to you.

EpicPandaForce · Accepted Answer · 2020-06-10 15:01:04Z

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).

Artem Motuzniy · Accepted Answer · 2020-06-10 15:05:32Z

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

Ruan_Lopes · Accepted Answer · 2019-11-14 22:10:46Z

-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

edited Nov 14, 2019 at 22:10

Ruan_Lopes

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answered May 23, 2019 at 20:58

Klaudia

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1 Comment

Duna Over a year ago

Your answer does not answer the passing back the arguments. It just remove the fragment from the navcontroller, that is it. Please reconsider your answer.

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