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Navigate with PopUpTo but not knowing what you root destination is - Navigation Architecture Component

Using Navigation Architecture Component we also have dynamic navigation from code like this in some cases:
navController.navigate(R.id.cartFragment)
Then when we need to navigate to a new root destination(back navigation will close the app) from that destination, we have no way of knowing what our current root destination is, so we don't know what to set the popUpTo destination to.
val navigationOptions = NavOptions.Builder().setPopUpTo(R.id.???, true).build()
navController.navigate(R.id.loginFragment, null, navigationOptions)
If we set it to a destination not in the backstack, then we get the warning log (from popBackStackInternal in NavController):
"Ignoring popBackStack to destination *:id/splashFragment as it was not found on the current back stack"
The case happens because we also have multiple cases before in the flow, where we set PopUpTo so dependant on the flow we have different root destinations.
I have looked at all avaliable methods on NavController and tried some reflection on mBackStack, but I was not able to figure out a way to clear the backstack.
How to clear the backstack when not knowing the current root destination?
Edit: Navigation graph example added
<fragment
android:id="#+id/navigation_cart"
android:name="ProjectsFragment_"
android:label="Cart"
tools:layout="#layout/fragment_cart" />
<fragment
android:id="#+id/loginFragment"
android:name="LoginFragment_"
android:label="Login"
tools:layout="#layout/fragment_login">
<--! Dynamic navigation to either Consent or Cart based on state -->
<action
android:id="#+id/action_login_to_home"
app:destination="#id/navigation_cart"
app:popUpTo="#id/loginFragment"
app:popUpToInclusive="true" />
<action
android:id="#+id/action_loginFragment_to_consentFragment"
app:destination="#id/consentFragment" />
<action
android:id="#+id/action_loginFragment_to_contactFragment"
app:destination="#id/contactFragment" />
</fragment>
<fragment
android:id="#+id/splashFragment"
android:name="SplashFragment_"
android:label="SplashFragment"
tools:layout="#layout/fragment_splash">
<--! Dynamic navigation to either Onboarding, Login or Cart based on state -->
</fragment>
<dialog
android:id="#+id/consentFragment"
android:name="ConsentFragment"
android:label="ConsentFragment"
tools:layout="#layout/fragment_consent" />
<fragment
android:id="#+id/onboardingIntroFragment"
android:name="OnboardingIntroFragment_"
android:label="OnboardingIntroFragment"
tools:layout="#layout/fragment_onboarding">
<action
android:id="#+id/action_onboardingIntroFragment_to_loginFragment"
app:destination="#id/loginFragment"
app:popUpTo="#id/onboardingIntroFragment"
app:popUpToInclusive="true" />
</fragment>
<dialog
android:id="#+id/contactFragment"
android:name="ContactFragment"
android:label="ContactFragment"
tools:layout="#layout/fragment_contact" />
Regarding the concrete cases above from the SplashFragment we will dynamic navigate to either Onboarding, Login or Cart based on state. If that we navigate to Login and after success login navigate dynamic to Cart.
I both cases of the general dynamic navigation we do not know what our root destination is, and though can't set popUpTo correctly. When called from Splash it is SplashFragment, when called from Login it is LoginFragment, or another case in checkout it could be CartFragment or another fragment that is root destination.
How to figure out either dynamically what the root destination is or just to clear the backstack as a part of navigation?
Though this is a bit simplified as there is more cases of the same pattern in our app.
Edit 2: Root destination definition
I define root destination as the destination to popUpTo with inclusive to clear the full backstack, så the backaction will close the app.
For example Splash -> Login will clear splash with popUpTo, then Login to Cart should clear the rest of the backstack but now the root destination is not Splash but Login as Splash was popped when going to Login.

We ended up solving it in two ways.
1) When we could figure out from our dynamic navigation location what the current root destination was we parsed that argument in to our dynamic Navigator.
object Navigator {
fun showStartFragment(navController: NavController, #IdRes currentDestination: Int) {
val navigationOptions = NavOptions.Builder().setPopUpTo(currentDestination, true).build()
if (!Settings.Intro.onboardingCompleted) {
navController.navigate(R.id.onboardingIntroFragment, null, navigationOptions)
} else {
val isLoggedIn = Settings.User.loggedIn
if (isLoggedIn) {
MainActivity.shared?.mainStateHandler?.showNextFragment(navController, currentDestination)
} else {
navController.navigate(R.id.loginFragment, null, navigationOptions)
}
}
}
}
2) But we also had the case where an asyn endpoint respone could result in, that the user must be logged out, do to expired token or the user has been blocked. To solve that we hacked the NavController to get the root destination with reflection.
fun NavController.getRootDestination(): NavDestination? {
val mBackStack = NavController::class.java.getDeclaredField("mBackStack").let {
it.isAccessible = true
return#let it.get(this) as Deque<*>
}
for (entry in mBackStack) {
val destination = Reflector.getMethodResult(entry, "getDestination") as NavDestination
if (destination !is NavGraph) {
return destination
}
}
return null
}
object Reflector {
fun getMethodResult(`object`: Any, methodName: String): Any? {
return `object`.javaClass.getMethod(methodName).let {
it.isAccessible = true
return#let it.invoke(`object`)
}
}
}

How to clear navigation Stack after navigating to another fragment in Android

Fragment XXX {} not associated with a fragment manager

I started using navigation component in my application and I am facing with the following problem.
My first fragment is LoginFragment. After a success login, the mainFragment is displayed. I want that when user is on mainFragment and press back button to not go back to loginFragment. For this I added these 2 lines in nav_graph : app:popUpTo="#+id/lovable_app_navigation" and app:popUpToInclusive="true" and it works well. Here is my navigation graph :
<?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/loginFragment">
<fragment
android:id="#+id/loginFragment"
android:name="com.xxx.LoginFragment"
android:label="LoginFragment"
tools:layout="#layout/login_fragment">
<action
android:id="#+id/dashboard_action"
app:destination="#id/mainFragment"
app:launchSingleTop="true"
app:popUpTo="#+id/app_navigation"
app:popUpToInclusive="true"/>
</fragment>
<fragment
android:id="#+id/mainFragment"
android:name="com.xxx.MainFragment"
android:label="MainFragment"
tools:layout="#layout/main_fragment">
<action
android:id="#+id/logout_action"
app:destination="#id/loginFragment"
app:launchSingleTop="true"
app:popUpTo="#+id/app_navigation"
app:popUpToInclusive="true"/>
</fragment>
<action
android:id="#+id/action_global_loginFragment"
app:destination="#id/loginFragment" />
</navigation>
The problem is that after a time, when my session expires, it doesn't matter where the user is in application, in which fragment, I must to display the LoginFragment over the all stack. I created a global action for this action_global_loginFragment. The problem is that when I navigate to LoginFragment I get this error :
java.lang.IllegalStateException: Fragment LoginFragment{1d6bd24 (829a6832-3480-4bcb-a3f6-7e2ba214d3ca)} not associated with a fragment manager.
If I remove popUpTo and popUpToInclusive it works fine, but then the back button functionality is affected, from mainFragment it goes back to loginFragment.
Any idea how to fixed this?
Thanks in advance.

The same issue was happening to me, I managed to solve it by wrapping the navigate method inside a view?.post call like so:
view?.post {
findNavController().navigate(SplashFragmentDirections.actionSplashFragmentToLoginFragment())
}

The problem is caused when you try to call findNavController() on a fragment that has been detached, if you're using Kotlin you can create an extension function like so
fun Fragment.findNavControllerSafely(): NavController? {
return if (isAdded) {
findNavController()
} else {
null
}
}
then use it in any fragment
findNavControllerSafely()?.navigate(/*pass here the nav directions>*/)
you can also surround it with try/catch but I do not recommend this as it will silently catch/ignore other exceptions that might be useful, try navigating through the source code of findNavController() to get a better feel of the kind of exceptions that are thrown

for me the problem was the fragment after restoration because of config change was the fragment manager was not valid in fragment so I had to get it directly from activities like this:
activity?.findNavController(R.id.nav_host_fragment)?.navigate(....)
or
activity?.supportFragmentManager?.setFragmentResultListener(.....)

I was facing the same issue today.
the problem was with the importing of the wrong file.
there are actually 3 files that can be imported.
import androidx.navigation.fragment.findNavController
This says findNavController()
import androidx.navigation.Navigation.findNavController
This says findNavController(Activity, Int)
import androidx.navigation.fragment.NavHostFragment.findNavController
This says findNavController(Fragment)
If I used 2nd one it gave an error Fragment not attached/associated with/to an Activity. (don't remember the exact error)
If I used 3rd one I was getting the same error as #Gabrielle
so, for me, the first one worked perfectly fine since it doesn't require either Activity or Fragment.

I've had this issue too and its very confusing to know whats wrong!
I found this URL That helped me a lot!:Android Navigation Component Issue
This guy suggest to create a function on every fragment, due to when using the findNavController() with a fragment that isn't NavHostFragment or isn't within NavHostFragment this exception will be thrown.
fun Fragment.getFragmentNavController(#IdRes id: Int) = activity?.let {
return#let Navigation.findNavController(it, id)
}
Then, you can all your navigation instance with the id just like this:
getFragmentNavController(R.id.shipping_host_nav).navigate(R.id.id_of_host_nav)

im cereate an extention for this issue , it work based on fragments lifecycle and kotlin
fun NavController.lifeCycleNavigate(lifecycle :LifecycleCoroutineScope, resId :Int) =
lifecycle.launchWhenResumed {
navigate(resId)
}
now we can use it simply with navController , like this
findNavController().lifeCycleNavigate(lifecycleScope , R.id.destination )

Navigation popUpTo and PopUpToInclusive aren't clearing the backstack

I'm new to the Android Jetpack Navigation architecture. I'm trying it out on a new app. There's one activity and a few fragments, two of them are login screen and email login screen. I defined those fragments in my navigations XML. The flow of the app is as follows:
Login screen → Email Login screen
What I want is, after navigating to the email login screen, when I press back, the app exits. Meaning the back-stack for login screen is removed. I know login screens aren't supposed to work that way, but I'm still just figuring things out.
I followed the documentation from Google's Get started with the Navigation component. It said, using app:popUpTo and app:popUpToInclusive="true" is supposed to clear the backstack, yet when I press back on email login screen, it still goes back to login instead of exiting.
So, here's what I've tried.
nav_main.xml
<fragment android:id="#+id/loginFragment"
android:name="com.example.myapp.ui.main.LoginFragment"
android:label="#string/login"
tools:layout="#layout/fragment_login" >
<action
android:id="#+id/action_login_to_emailLoginFragment"
app:destination="#id/emailLoginFragment"
app:popEnterAnim="#anim/slide_in_right"
app:popExitAnim="#anim/slide_out_right"
app:popUpTo="#+id/emailLoginFragment"
app:popUpToInclusive="true"/>
</fragment>
<fragment android:id="#+id/emailLoginFragment"
android:name="com.example.myapp.ui.main.EmailLoginFragment"
android:label="EmailLoginFragment"
tools:layout="#layout/fragment_login_email" />
LoginFragment.kt
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
binding.emailLoginButton.setOnClickListener {
findNavController().navigate(R.id.action_login_to_emailLoginFragment)
}
return binding.root
}
I gave a click event to a button. In it, I used the Navigation Controller to navigate to the email login screen by giving it the action's ID. In the <action>, there are app:popUpTo and app:popUpToInclusive="true".
After reading the documentation over and over, as well as reading plenty of StackOverflow questions, I found those properties are supposed to remove my login screen off the back-stack. But they don't. The button does navigate to the email login screen, but when I press back, it still goes back to login screen instead of exiting the app. What am I missing?

<action
android:id="#+id/action_login_to_emailLoginFragment"
app:destination="#id/emailLoginFragment"
app:popEnterAnim="#anim/slide_in_right"
app:popExitAnim="#anim/slide_out_right"
app:popUpTo="#+id/loginFragment"
app:popUpToInclusive="true"/>
Your popUpTo is going back to the email login, and then popping it because of the inclusive.
If you will change the popUpTo to your login fragment, it will be navigated back to, and popped as well because of the inclusive flag, which will result in your desired behaviour.

I write this answer for people who have not completely understood the
way popUpTo works and I hope its example helps someone because most
examples for navigation are repetitive in most sites and do not show
the whole picture.
In any <action> if we write a value for app:popUpTo, it means we want to delete some of the fragments from the back stack just after completing the action, but which fragments are going to be removed from the back stack when action is completed?
Its order is Last In First Out so:
All fragments between the last fragment and the fragment defined in popUpTo will be removed.
And if we add app:popUpToInclusive="true", then the fragment defined
in popUpTo will also be removed.
Example:
Consider fragments from A to G in a navigation graph like this:
A->B->C->D->E->F->G
We can go from A to B and then from B to C and so on. Consider the following two actions:
An action E->F we write:
<action
...
app:destination="#+id/F"
app:popUpTo="#+id/C"
app:popUpToInclusive="false"/>
And for F->G we write:
<action
...
app:destination="#+id/G"
app:popUpTo="#+id/B"
app:popUpToInclusive="true"/>
Then after going from E to F using the action E->F, the fragments between the last fragment (F) and C (which is defined in popUpTo of E->F) will be removed. The fragment C will not be removed this time because of app:popUpToInclusive="false" so our back stack becomes:
A->B->C->F (F is currently on Top)
Now if we go to fragment G using action F->G :
all fragments between the last fragment(G) and B (which is defined in popUpTo of F->G ) will be removed but this time the fragment B will also be removed because in F->G action we wrote app:popUpToInclusive="true" . so back stack becomes:
A->G (G is on top now)

These 2 lines make the trick works:
If you want to go from A to B and expect to finish A:
You need to call B with this action:
<fragment
android:id="#+id/fragmentA"
tools:layout="#layout/fragment_a">
<action
android:id="#+id/action_call_B"
app:destination="#+id/fragmentB"
app:popUpTo="#id/fragmentA"
app:popUpToInclusive="true" />
</fragment>
<fragment
android:id="#+id/fragmentB"
tools:layout="#layout/fragment_b">
</fragment>
If you put log to your fragments you can see that fragmentA is destroyed after calling fragmentB with this action.

You can do it in XML just like this answer does, or you can also do it programmatically:
NavOptions navOptions = new NavOptions.Builder().setPopUpTo(R.id.loginRegister, true).build();
Navigation.findNavController(mBinding.titleLogin).navigate(R.id.login_to_main, null, navOptions);

Let's say that your app has three destinations—A, B, and C—along with actions that lead from A to B, B to C, and C back to A. The corresponding navigation graph is shown in figure
With each navigation action, a destination is added to the back stack. If you were to navigate repeatedly through this flow, your back stack would then contain multiple sets of each destination (A, B, C, A, B, C, A, and so on). To avoid this repetition, you can specify app:popUpTo and app:popUpToInclusive in the action that takes you from destination C to destination A, as shown in the following example:
<fragment
android:id="#+id/c"
android:name="com.example.myapplication.C"
android:label="fragment_c"
tools:layout="#layout/fragment_c">
<action
android:id="#+id/action_c_to_a"
app:destination="#id/a"
app:popUpTo="#+id/a"
app:popUpToInclusive="true"/>
After reaching destination C, the back stack contains one instance of each destination (A, B, C). When navigating back to destination A, we also popUpTo A, which means that we remove B and C from the stack while navigating. With app:popUpToInclusive="true", we also pop that first A off of the stack, effectively clearing it. Notice here that if you don't use app:popUpToInclusive, your back stack would contain two instances of destination A

popUpTo its to define the place that you want to go when you press back. If you set popUpInclusive = true, the navigation skipe that place too ( in popUpTo ).

Sample: A -> B -> A
FragmentB.kt
Attempts to pop the controller's back stack
private fun popBackStackToA() {
if (!findNavController().popBackStack()) {
// Call finish on your Activity
requireActivity().finish()
}
}
Back Stack

I faced a similar problem and my approach was simple. In the navigation graph, you have to designate the starting screen. Mine was:
app:startDestination="#id/webview"
It's called the start destination, it is the first screen users see when opening your app, and it's the last screen users see when exiting your app.
If you do not wish your login activity to be shown as you exit the app, just remove it as the start destination and use the fragment that you wish to show last in your case, It's the Email Login screen.
<?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/nav"
app:startDestination="#id/Email Login screen">
Also, make sure you override the onBackPressed() method from the host activity code as:
override fun onBackPressed() {
finish()
super.onBackPressed()
}
Now that you have removed the login fragment as the start destination, it's now not obvious what fragment will be shown first when the app opens.
Add a method to implement that in the host activity and call it from the oncreate(). In my case,i created initContent() to handle that logic. This was the code:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
navController = navHostFragment.navController
if (savedInstanceState == null) {
initContent()
}
}
private fun initContent() {
if (isNetworkConnected()) {
navController.navigate(R.id.webView)
} else {
navController.navigate(R.id.noInternetFragment)
}
}
Hope this helps someone.

Navigation Architecture Component: How i can navigate a fragment from the back stack?

i have two fragments A and B i am using navigation controller to navigate from A To B when i come back to A the navigation controller create another instance of A !! not calling the old instance from the stack and increase the sack size in this case the stack size will be 3 fragments,
how i can fix this issue ?
here is my graph.xml
<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/home_dest"
app:startDestination="#id/home_dest">
<fragment
android:id="#+id/a_dest"
android:name="com.intcore.e_commerce.e_commerce.ui.homefragment.HomeFragment"
android:label="#string/home"
tools:layout="#layout/fragment_home" />
<fragment
android:id="#+id/b_dest"
android:name="com.intcore.e_commerce.e_commerce.ui.favoritesfragment.FavoritesFragment"
android:label="#string/favorites"
tools:layout="#layout/fragment_favorites" /></avigation>
and here is my code the i use to navigate.
void onAClicked() {
Navigation.findNavController(this, R.id.nav_host_fragment).navigate(R.id.a_dest);
}
void onBClicked() {
Navigation.findNavController(this, R.id.nav_host_fragment).navigate(R.id.b_dest);
}

For the action connecting the nav_host_fragment to the a_dest, you need to set the pop behavior to popTo nav_host_fragment inclusive(in the navigation editor).
Repeat the same for connecting nav_host_fragment to b_dest.
PopTo inclusive pops off everything on the back stack including the referenced fragment transaction.
Create an action connecting the a_dest to the nav_host_fragment and from b_dest to the nav_host_fragment. For each fragment, Select PopTo nav_host_fragment with the inclusive flag turned off.

How to disable UP in Navigation for some fragment with the new Navigation Architecture Component?

I am trying out the new Navigation Architecture Component, and I can't figure out how to do this:
I have 1 Activity (MainActivity) + 3 Fragments:
SplashFragment (Home)
MainFragment
SignUpFragment
I would like to use SplashFragment to determine if I should navigate to MainFragment or SignUpFragment, but once it reaches either of those 2, you should not be able to pop back to SplashFragment. How can I do that with the new navigation component?
I tried popBackStack before and after calling navigate(R.id.action_xxx), but neither of them work (which make sense: before it has nothing to pop; after it just closes the fragment that just got added). Does that mean the only way to do that is to override onBackPress to intercept it and make sure navigateUp does not get call in those cases?
Thanks!

First, add attributes app:popUpTo='your_nav_graph_id' and app:popUpToInclusive="true" to the action tag.
<fragment
android:id="#+id/signInFragment"
android:name="com.glee.incog2.android.fragment.SignInFragment"
android:label="fragment_sign_in"
tools:layout="#layout/fragment_sign_in" >
<action
android:id="#+id/action_signInFragment_to_usersFragment"
app:destination="#id/usersFragment"
app:launchSingleTop="true"
app:popUpTo="#+id/main_nav_graph"
app:popUpToInclusive="true" />
</fragment>
Second, navigate to the destination, using the above action as parameter.
findNavController(fragment).navigate(SignInFragmentDirections.actionSignInFragmentToUserNameFragment())
NOTE: If you navigate using method navigate(#IdRes int resId), you won't get the desired result. Hence, I used method navigate(#NonNull NavDirections directions).

This worked for me in alpha05 release. Add app:popUpTo="#id/nav_graph" in the action tag(inside your nav_graph.xml file).
Here "#id/nav_graph is the id of my graph or also called as the Root.
<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/nav_graph"
app:startDestination="#id/startFragment">
.......
<action
android:id="#+id/action_startFragment_to_homeFragment"
app:destination="#id/homeFragment"
app:popUpTo="#id/nav_graph"/>
.......
You can also do this in design tab:- select "SplashFragment" and select the action you want to change and then pick "root" for "Pop To"

WARNING: clearTask has been deprecated and will be remove in future release, not sure what the solution is. Please follow this issue for now to keep up to date
Oh after 10 minutes finally found the key: use clearTask.
All I have to do is add app:clearTask="true" to that specific action, or use .navigate(R.id.actionXXXX, null, NavOptions.Builder().setClearTask(true).build()), and it's done. Just make sure you add it to all the children of SplashFragment (in this case, both MainFragment and SignUpFragment).

So if you have splash fragment and main fragment and you don't want to go back to splash fragment after the main fragment below method you can achieve this
<fragment
android:id="#+id/splashFragment"
android:name="com.example.youappname.views.SplashFragment"
android:label="fragment_splash"
tools:layout="#layout/fragment_splash">
<action
android:id="#+id/action_splashFragment_to_mainFragment"
app:destination="#id/mainFragment"
app:popUpTo="#id/splashFragment"
app:popUpToInclusive="true"/>
</fragment>
In you Kotlin Splash Fragment:
private lateinit var navController: NavController
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
navController = Navigation.findNavController(view)
}
private fun navigateToMainFrag() {
navController.navigate(R.id.action_splashFragment_to_mainFragment)
}
Now when you press back button it will close the app instead of showing the splash screen

For anyone wanted to do this purely in code:
Navigation.findNavController(v)
.navigate(R.id.action_splashFragment_to_userProfileFragment2, null,
new NavOptions.Builder().setPopUpTo(R.id.splashFragment, true).build())

The sample solution is add a onBackPressedDispatcher on Owner Activity of fragment/navigation:
https://developer.android.com/guide/navigation/navigation-custom-back#implement_custom_back_navigation