NavType should also support serializing as a value [247637434]

Fixed

Feature Request

Status Update

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Description

il...@google.com

created issue #1

Sep 19, 2022 11:51PM

Component used: Navigation

Version used: 2.6.0-alpha01

Right now when providing a custom type half of the serialization/deserialization logic need to live in the NavType, but the other half, serializing the value into the route to call navigate with, is completely separate:

val SearchParametersType = object : NavType<SearchParameters>(
  isNullableAllowed = false
) {
  // ...

  override fun parseValue(value: String): SearchParameters {
    return Json.decodeFromString<SearchParameters>(value)
  }
}

and later

val params = SearchParameters("rose", listOf("available"))
val searchArgument = Uri.encode(Json.encodeToString(params))
navController.navigate("${nav_routes.plant_search}/$searchArgument")

It would be nice if NavType could be the single source of truth for both sides of the equation, thus allowing you to write something like:

override fun serializeAsValue(value: SearchParameters): String {
  return Uri.encode(Json.encodeToString(value))
}

And use it like:

val params = SearchParameters("rose", listOf("available"))
val searchArgument = SearchParametersType.serializeAsValue(params)
navController.navigate("${nav_routes.plant_search}/$searchArgument")

By default, I think this method should just call toString() on the class. The one exception could be StringType, which could Uri.encode() for you.

Comments

ap...@google.com <ap...@google.com> #2Oct 13, 2022 08:39PM

Oh I forgot to mention that I thought it might be connected to this issue: https://issuetracker.google.com/issues/243778589. But after trying 2.5.2 I can say that the issue persists.

cl...@google.com <cl...@google.com> #3Oct 13, 2022 08:53PM

Marked as fixed.

Please provide a minimal sample project along with the minimal steps to recreate the issue in the project.

na...@google.com <na...@google.com> #4Nov 9, 2022 06:28PM

Sorry for the delay. I got a working example here: https://github.com/Del-S/issues. The project is set up to crash when navigating to ThirdFragment (nested nav graph) with poping the graph.

I poked into it a little bit and it seems to be connected to SafeArgs gradle plugin. When safe args is used to navigate to ThirdFragment (with nested graph poped) it will try to recreate te parent but there were no arguments passed so it crashes.

Steps to reproduce:

Navigate from Second Fragment to Child nav graph (with non-nullable parameters).
Navigate to Third fragment using SafeArgs and the app crashes.

Crash log:

Process: cz.dels.issues, PID: 1743
java.lang.NullPointerException: null cannot be cast to non-null type kotlin.Long
at androidx.navigation.NavType$Companion$LongType$1.get(NavType.kt:352)
at androidx.navigation.NavType$Companion$LongType$1.get(NavType.kt:342)
at androidx.navigation.NavArgument.verify(NavArgument.kt:76)
at androidx.navigation.NavDestination.addInDefaultArgs(NavDestination.kt:502)
at androidx.navigation.NavController.addEntryToBackStack(NavController.kt:1865)
at androidx.navigation.NavController.addEntryToBackStack$default(NavController.kt:1813)
at androidx.navigation.NavController$navigate$4.invoke(NavController.kt:1721)
at androidx.navigation.NavController$navigate$4.invoke(NavController.kt:1719)
at androidx.navigation.NavController$NavControllerNavigatorState.push(NavController.kt:287)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:246)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:162)
at androidx.navigation.NavController.navigateInternal(NavController.kt:260)
at androidx.navigation.NavController.navigate(NavController.kt:1719)
at androidx.navigation.NavController.navigate(NavController.kt:1545)
at androidx.navigation.NavController.navigate(NavController.kt:1472)
at androidx.navigation.NavController.navigate(NavController.kt:1930)
at cz.dels.issues.SecondFragment.onViewCreated$lambda-0(SecondFragment.kt:38)
at cz.dels.issues.SecondFragment.$r8$lambda$XDYnOS_cYrafiNQ5rcCu1WCn0IE(Unknown Source:0)
at cz.dels.issues.SecondFragment$$ExternalSyntheticLambda0.onClick(Unknown Source:2)

Note: If in step 2 SaveArgs is not used then navigation works correctly. More information is here: https://github.com/Del-S/issues/blob/master/app/src/main/java/cz/dels/issues/SecondFragment.kt#L37.

Issue 247637434

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Comments

ap...@google.com <ap...@google.com> #2Oct 13, 2022 08:39PM

cl...@google.com <cl...@google.com> #3Oct 13, 2022 08:53PM

na...@google.com <na...@google.com> #4Nov 9, 2022 06:28PM

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