Pass data/bundle using navigateUp in Android Navigation Component

According to developer.android.com, you can use common for fragments where you want to share data ViewModel using their activity scope.

Here are steps:

1. Create view model which will keep the data:

class SharedViewModel : ViewModel() {
    val dataToShare = MutableLiveData<String>()

    fun updateData(data: String) {
        dataToShare.value = data
    }
}

2. Observe data changes in Fragment1:

class Fragment1 : Fragment() {

    private lateinit var viewModel: SharedViewModel

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProviders.of(activity!!).get(SharedViewModel::class.java)
        viewModel.dataToShare.observe(this, Observer<String> { dataFromFragment2 ->
            // do something with data
        })
    }
}

3. Update data in Fragment2 and if you're handling navigation properly, now, you should be able to receive data changes on Fragment1:

class Fragment2 : Fragment() {

    private lateinit var viewModel: SharedViewModel

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProviders.of(activity!!).get(SharedViewModel::class.java)

        updateDataButton.setOnClickListener { v ->
            viewModel.updateData("New data for fragment1")
        }
    }
}

I hope answer helps.

Please use the OFFICIAL androidx's components. setFragmentResultListener() and setFragmentResult() methods:

implementation "androidx.fragment:fragment-ktx:1.3.5"

Cheers ;)

You can use NavigationResult library. Basically it's startActivityForResult but for Fragments in Navigation component.

To pop destinations when navigating from one destination to another, add an app:popUpTo attribute to the associated <action> element. To navigate from fargment2 to Fragment1 with arguments, specify in the navigation graph the action of the caller fragment and the arguments of the destination fragment :

<fragment
    android:id="@+id/fragment2"
    android:name="com.example.myapplication.Fragment2"
    android:label="fragment_2"
    tools:layout="@layout/fragment_2">

    <action
        android:id="@+id/action_2_to_1"
        app:destination="@id/fragment1"
        app:popUpTo="@+id/fragment1"/>
</fragment>
<fragment
    android:id="@+id/fragment1"
    android:name="com.example.myapplication.Fragment1"
    android:label="fragment_1"
    tools:layout="@layout/fragment_1">

        <argument
            android:name="someArgument"
            app:argType="string"
            app:nullable="false"
            android:defaultValue="Hello Word"/>
</fragment>

In your Fragment2 class, you call your action and pass your argument:

   val action = Fragment2Directions.action2To1("MY_STRING_ARGUMENT")
        findNavController().navigate(action)

You should use static variables/companion objects, because it is better than shared viewmodel as it is not simple/nice architecture. As it it not straightforward, I think it is the best way.

To navigateUp From FragmentB to FragmentA

FragmentB:

isBackpressed = true
findNavController().navigateUp() 

FragmentA:

onViewCreated() {
    // todo
    if(isBackpressed) {
         isBackpressed = false
         // do whatever you want
    }
}