[ERROR/EXCEPTION] java.lang.IllegalArgumentExceptionNavigation action/destination package:id/CNestedFragment cannot be found from the current destination a(package:id/bNestedFragment) label=BNestedFragment class=package.ui.common.BNestedFragment

[이슈] navigation 시 app crash

 

[원인] netsted graph는 startDestination만을 통해 접근 가능

nested graph 접근 가능 방향

Nested Graph Fragment -> Root Graph Fragment : O
Root Graph Fragment -> Nested Graph Fragment : X

 

명시적으로 navigate한 경우 발생하는데, 내 프로젝트의 경우 state에 따른 타이밍 이슈 때문에 발생함

 

[재현 조건]

초기 Navigation BackQueue : Root Graph - Nested Graph - AFragment

중간 Navigation BackQueue : Root Graph - Nested Graph - AFragment - CFragment

종결 Navigation BackQueue : Root Graph - Nested Graph - AFragment - CFragment - BFragment

 

Single Activity를 가지고 그 안에서 Fragment로 이동하는 Navigation의 기본 구조대로 진행

 

1. 초기 상태에서 Activity의 특정 state collect가 수행되어 CFragment로 navigate

2. 초기 상태에서 AFragment의 특정 state collect가 수행되어 BFragment로 navigate(여기서는 A, B Fragment가 동일 Nested Graph에 있다고 가정(이동가능하다는 가정하에))

 

1이 먼저 수행되면서 2가 이후 수행 시, Root Graph Fragment -> Nested Graph Fragment : X 를 수행하는 것이므로 에러 발생

 

[해결]

2를 방지하기 위해서 collect함수를 repeatOnLifeCycle로 감쌌지만 동일 문제 발생

 viewLifecycleOwner.lifecycleScope.launch {
            viewLifecycleOwner.lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED) {
                collectState(this)
            }
  }

 

repeatOnLifecycle(Lifecycle.State.STARTED)는 onStart()~onPause() 직전까지 수행

하지만, 1번과 같이 navigate가 불리는 순간 onPause의 수행되지 않고 collect가 진행됨(이후, onStop()이 바로 호출됨)

-> 왜그런지는 WIP

 

이를 방지하기 위해, Lifecycle.State.RESUMED로 변경하면 정상 동작함

 

[STARTED]
2023-07-18 14:09:06.090  9946-9946  AFragment                       E  AFragment onCreateView()
2023-07-18 14:09:06.105  9946-9946  AFragment                       E  AFragment onStart()
2023-07-18 14:09:06.112  9946-9946  AFrag...collectState            E  AFragment collectState : null
2023-07-18 14:09:06.212  9946-9946  MainActivi...collectState       E  MainActivity go to CFragment
2023-07-18 14:09:06.234  9946-9946  AFrag...collectState            E  AFragment collectState : CHANGED
2023-07-18 14:09:06.235  9946-9946  AFrag...collectState            E  AFragment collectState go to AFragment
2023-07-18 14:09:10.647  9946-9946  AndroidRuntime                  E  FATAL EXCEPTION: main
Process: , PID: 9946
java.lang.IllegalArgumentException: Navigation action/destination BFragment cannot be found from the current destination Destination(CFragment) label=CFragment class=package.CFragment
    at androidx.navigation.NavController.navigate(NavController.kt:1540)
    at androidx.navigation.NavController.navigate(NavController.kt:1472)
    at package.AFragment$collectState$1$1.emit(AFragment.kt:96)
    at package.AFragment$collectState$1$1.emit(AFragment.kt:89)
    at kotlinx.coroutines.flow.StateFlowImpl.collect(StateFlow.kt:398)
    at kotlinx.coroutines.flow.StateFlowImpl$collect$1.invokeSuspend(Unknown Source:15)

Navigation BackQueue
2023-07-18 14:09:06.231  9946-9946  MainActivity$onCreate                D  navBackStackEntry ===============================
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = root_graph
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = nested_graph
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = AFragment
2023-07-18 14:09:06.233  9946-9946  MainActivity$onCreate                D  navBackStackEntry = CFragment

 

 

[RESUMED]
2023-07-18 14:07:46.807  9328-9328  AFragment                       E  AFragment onCreateView()
2023-07-18 14:07:46.821  9328-9328  AFragment                       E  AFragment onStart()
2023-07-18 14:07:46.909  9328-9328  MainActivi...collectState       E  MainActivity go to CFragment
2023-07-18 14:07:46.944  9328-9328  AFragment                       E  AFragment onStop()

Navigation BackQueue
2023-07-18 14:09:06.231  9946-9946  MainActivity$onCreate                D  navBackStackEntry ===============================
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = root_graph
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = nested_graph
2023-07-18 14:09:06.232  9946-9946  MainActivity$onCreate                D  navBackStackEntry = AFragment
2023-07-18 14:09:06.233  9946-9946  MainActivity$onCreate                D  navBackStackEntry = CFragment