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il...@google.com
ma...@gmail.com
So there does seem to be a bug in Navigation that causes this to fail.
When it navigates with popUpTo and removes SecondFragment, that removal in fragment is set for a frame later and before it is actually removed the navigate call in the onViewCreated of SecondFragment enqueues another call to add it back. But we still need to destroy SecondDetailFragment which ends up marking the NavBackStackEntry associated with SecondFragment as complete before navigation has received the call from the fragment that it has been added back. So by the time it hits this check, the SecondFragment is in the correct state, but Navigation has no way of referencing it so it assumes that it is not associated with an entry.
But this is not the way this type of situation should be implemented. Instead of having the destinations as part of the NavGraph, they should:
- be managed by the childFragmentManager of
SecondFragment. So instead of going back toSecondFragmentjust to go somewhere else, each of the fragments take the entire content ofSecondFragmentand are swapped out. - for some sort of a/b testing, set different graphs in the Activity. The graphs would keep the same
SecondFragmentid, but swap out the names and then you choose the correct graph based on the condition.
ch...@moqi.co.uk
il...@google.com
- Have
SecondFragmentas part of your graph and then inside ofSecondFragmentcall thechildFragmentManagerandreplacewith the fragment you actually want to show, whether that isSecondTypeOneorSecondTypeTwo. - Create different graphs and follow along with the
docs
ap...@google.com
shardViewModel.onGetTypeSecond.observe(viewLifecycleOwner) { isType1 ->
if (isType1) {
val graph = findNavController().graph
val carInstallmentNavGraph =
graph.findNode(R.id.nav_second) as NavGraph
carInstallmentNavGraph.setStartDestination(R.id.secondTypeOneFragment)
findNavController().navigate(SecondFragmentDirections.actionSecondFragmentToSecondTypeOneFragment())
} else {
val graph = findNavController().graph
val carInstallmentNavGraph =
graph.findNode(R.id.nav_second) as NavGraph
carInstallmentNavGraph.setStartDestination(R.id.secondTypeTwoFragment)
findNavController().navigate(SecondFragmentDirections.actionSecondFragmentToSecondTypeTwoFragment())
}
}
and removed app:popUpTo="@id/secondFragment" and app:popUpToInclusive="true"
<fragment
android:id="@+id/secondFragment"
android:name="com.example.navigationdeeplink.SecondFragment"
android:label="fragment_second"
tools:layout="@layout/fragment_second" >
<action
android:id="@+id/action_secondFragment_to_secondTypeOneFragment"
app:destination="@id/secondTypeOneFragment" />
<action
android:id="@+id/action_secondFragment_to_secondTypeTwoFragment"
app:destination="@id/secondTypeTwoFragment"
app:popUpTo="@id/secondFragment" />
</fragment>
Description
android.arch.navigation:navigation-fragment-ktx
android.arch.navigation:navigation-ui-ktx
Version used:
1.0.0-alpha05
Devices/Android versions reproduced on:
-SM-A510F, Android 7.0
-Emulator x86_64 API 28
Sample project:
Description:
Having this structure:
nav_graph.xml
<navigation
android:id="@+id/nav_graph"
app:startDestination="@id/startFragment">
<fragment
android:id="@+id/startFragment"
android:name="com.example.navbug.StartFragment"
android:label="StartFragment"
tools:layout="@layout/fragment_start">
<action
android:id="@+id/action_startFragment_to_nested_nav_graph"
app:destination="@id/nested_nav_graph" />
</fragment>
<include app:graph="@navigation/nested_nav_graph" />
</navigation>
nested_nav_graph.xml
<navigation
android:id="@+id/nested_nav_graph"
app:startDestination="@id/nestedStartFragment">
<fragment
android:id="@+id/nestedStartFragment"
android:name="com.example.navbug.NestedStartFragment"
android:label="NestedStartFragment">
<action
android:id="@+id/action_nestedStartFragment_to_nestedSecondFragment"
app:destination="@id/nestedSecondFragment"
app:popUpTo="@+id/nestedStartFragment"
app:popUpToInclusive="true" />
</fragment>
<fragment
android:id="@+id/nestedSecondFragment"
android:name="com.example.navbug.NestedSecondFragment"
android:label="NestedSecondFragment" />
</navigation>
I want to achieve this navigation pattern:
StartFragment => NestedStartFragment => NestedSecondFragment =(back)=> StartFragment
I'm trying to implement this by setting the action NestedStartFragment=>NestedSecondFragment with the options [popUpTo=NestedStartFragment, popUpToInclusive=true], so that the resulting stack would be:
0. NestedSecondFragment
1. NestedNavGraph
2. StartFragment
3. NavGraph
When navigating from NestedStartFragment to NestedSecondFragment, the following execption occurs:
java.lang.IllegalArgumentException: Navigator androidx.navigation.fragment.FragmentNavigator@ccc9092 reported navigation to unknown destination id com.example.navbug:id/nestedSecondFragment
at androidx.navigation.NavController$2.onNavigatorNavigated(NavController.java:142)
at androidx.navigation.Navigator.dispatchOnNavigatorNavigated(Navigator.java:217)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:207)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:45)
at androidx.navigation.NavDestination.navigate(NavDestination.java:407)
at androidx.navigation.NavController.navigate(NavController.java:683)
at androidx.navigation.NavController.navigate(NavController.java:630)
at androidx.navigation.NavController.navigate(NavController.java:618)
at com.example.navbug.NestedStartFragment$onViewCreated$1.onClick(Fragments.kt:31)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Right before the navigation, the stack is:
0. NestedStartFragment
1. NestedNavGraph
2. StartFragment
3. NavGraph
When NestedStartFragment is popped on my request, NestedNavGraph is also popped because
"// We never want to leave NavGraphs on the top of the stack" (from NavController.onNavigatorNavigated)
with the effect that eventually the requested destination NestedSecondFragment is pruned from the graph and cannot be reached anymore.
Unless I'm doing something wrong, it seems that NavGraph automatic popping should be avoided if the final destination actually belongs to it.