Navigation component SingleTask launching of fragment navigation

Issue

I am using Navigation Component to build my application. I would like to implement SingleTask launch mode in the fragment navigation how can I achieve it?

For more clarity, I will detail my problem.

I have a HomeFragement(Lets Fragment A) and from that I have defined actions to the inner screens

Fragment A > Fragment B > Fragment C > Fragment D

I have a BaseFragment which extends all the above fragments in which I have implemented back click and its action using findNavController().popBackStack()

In Fragment D when the user clicks the back button as expected, it is navigating back to Fragment C. My problem comes when I have called an action whose destination fragment is Fragment A. I am calling this action on a successful event in Fragment D, that action also works well. But when the user press the back button from Fragment A it goes to Fragment C, the next back click goes to Fragment B, then the next back click to FRagment A. I should destroy Fragment B and Fragment C on the successful event called in Fragment D and should resume Fragment A.

I know this flow can be achieved by using launch mode as SingleTask of the first screen(Fragment A) if it is an Activity instead of Fragment.

My navigation graph XML file

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/app_navigation"
    app:startDestination="@id/fragmentA">

    <fragment

        android:id="@+id/fragmentA"
        android:name="FragmentA"
        
        tools:layout="@layout/fragment_a">
        <action
            android:id="@+id/action_FragmentA_to_FragmentB"
            app:destination="@id/dashboardFragment"
            app:launchSingleTop="true"
            app:popUpTo="@+id/main_nav_graph"
            app:popUpToInclusive="true" />
    </fragment>
   <fragment

        android:id="@+id/fragmentB"
        android:name="FragmentB"
        
        tools:layout="@layout/fragment_b">
        <action
            android:id="@+id/action_FragmentB_to_FragmentC"
            app:destination="@id/dashboardFragment"
            app:launchSingleTop="true"
            app:popUpTo="@+id/main_nav_graph"
            app:popUpToInclusive="true" />
    </fragment>
<fragment

        android:id="@+id/fragmentC"
        android:name="FragmentC"
        
        tools:layout="@layout/fragment_c">
        <action
            android:id="@+id/action_fragemntC_to_fragementA"
            app:launchSingleTop="true"
            app:popUpToInclusive="true"
            app:destination="@id/deliveriesFragment" />
    </fragment>
   </navigation>

Solution

But when the user press the back button from Fragment A it goes to Fragment C, the next back click goes to Fragment B, then the next back click to FRagment A.

If I understand correctly, your Fragment A is the start destination, like a main page, and you want the behavior of "whenever I come back to Fragment A, the next back button I click should exit the app", right?

If so, try to add action from any Fragment to Fragment A and set:

app:popUpTo="@id/fragmentA"
app:popUpToInclusive="true" />

It should look like this:

Demo: https://youtu.be/LNyk_FEkZoA

Answered By - Sam Chen