Navigation Component .popBackStack() with arguments

Just came across setFragmentResult(), pretty easy to use. The docs on this are here.

If you are navigating: Fragment A -> Fragment B -> Fragment A Add this to fragment A:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setFragmentResultListener("requestKey") { requestKey, bundle ->
        shouldUpdate = bundle.getBoolean("bundleKey")
    }
}

Then in fragment B add this line of code:

setFragmentResult("requestKey", bundleOf("bundleKey" to "value to pass back"))
// navigate back toFragment A

When you navigate back to fragment A the listener will trigger and you'll be able to get the data in the bundle out.

It's a bit late for this answer but someone may find it useful. In the updated versions of the navigation component library it is now possible to pass data while navigating back.

Suppose the stack is like this

FragmentA --> FragmentB.

We are currently now in FragmentB and we want to pass data when we go back to FragmentA.

Inside FragmentAwe can create an observer with a key:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val navController = findNavController()
// Instead of String any types of data can be used
navController.currentBackStackEntry?.savedStateHandle?.getLiveData<String>("key")
    ?.observe(viewLifecycleOwner) { 

    }
}

Then inside FragmentB if we change its value by accessing previous back stack entry it will be propagated to FragmentA and observer will be notified.

val navController = findNavController()
navController.previousBackStackEntry?.savedStateHandle?.set("key", "value that needs to be passed")
navController.popBackStack()