BottomNavigationView - Multiple start destinations on back stack [253256629]

Fixed

Bug

Status Update

No update yet.

Description

po...@gmail.com

created issue #1

Oct 12, 2022 05:54PM

Component used: Navigation / NavigationUI Version used: 2.5.2 Devices/Android versions reproduced on: OnePlus 8T / Android 12

I'm using a menu resource file which is bound to a BottomNavigationView. Also I'm setting up the navigation like so NavigationUI.setupWithNavController(bottomNavigationView, navController, false) which means I'm using the experimental version of this API.

I don't want the state of each menu item to be saved since I want to come back to the respective start destination if a BottomNavigationView item gets reselected. So regardless of how deep I got in a navigation graph a reselection of the same item takes you back to the start destination.

I'm using a navGraph which consists of several nested navGraphs like so:

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/navigation"
    app:startDestination="@id/destination_one">

    <include app:graph="@navigation/one_navigation" />

    <include app:graph="@navigation/two_navigation" />

    <include app:graph="@navigation/three_navigation" />

    <include app:graph="@navigation/four_navigation" />
</navigation>

The one_navigation could look like this:

<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/destination_one"
    app:startDestination="@id/destination_fragment_one">

    <fragment
        android:id="@+id/destination_fragment_one"
        android:name="com.example.OneFragment"
        android:label="@string/bottom_navigation_one"
        tools:layout="@layout/fragment_one">
    </fragment>
</navigation>

It works pretty good so far, the point is when I click the first BottomNavigationView's menu item N times I got the destination N+1 times on my back stack. If I wanted to leave the app by triggering the system's back navigation I'd have to do it N+1 times.

So I actually expect the startDestination to only exist once on the back stack regardless of how often I click the respective menu item setup with the above mentioned API.

Comments

il...@google.com <il...@google.com> #2Oct 12, 2022 06:07PM

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.

po...@gmail.com <po...@gmail.com> #3Oct 12, 2022 06:35PM

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

il...@google.com <il...@google.com> #4Oct 12, 2022 06:57PM

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.

po...@gmail.com <po...@gmail.com> #5Oct 13, 2022 05:32PM

Ups a typo: Navigate from ~~Second~~ First Fragment to Child nav graph (with non-nullable parameters).

Note: sorry for the spam but I am not able to edit my own comment.

il...@google.com <il...@google.com> Oct 18, 2022 08:52PM

Assigned to jb...@google.com.

jb...@google.com <jb...@google.com> #6Oct 21, 2022 12:14AM

Reassigned to cl...@google.com.

This has been fixed and will be available in navigation 2.6.0-alpha08

po...@gmail.com <po...@gmail.com> #7Oct 21, 2022 08:02AM

Project: platform/frameworks/support
Branch: androidx-main

commit 6b358154b794a0456b089ac8e548bfb830dd6c22
Author: Clara Fok <clarafok@google.com>
Date: Tue Mar 14 17:56:12 2023

Fix missing non-nullable arg when rebuilding hierarchy

When navigating with NavDirections, args is populated with an empty bundle. This causes issue when we rebuild parent hierarchy while adding a new entry to NavBackStack. If the Entry being rebuilt contains a non-nullalbe arg, i.e. Long, this empty bundle will cause an exception.

Test: ./gradlew navigation:navigation-runtime:cC
Bug: 249988437
Change-Id: I5c8ce739ad9a3428c8a8de13eae391bfff0db5df

M navigation/navigation-runtime/src/androidTest/java/androidx/navigation/NavControllerTest.kt
M navigation/navigation-runtime/src/main/java/androidx/navigation/NavController.kt

https://android-review.googlesource.com/2488855

cl...@google.com <cl...@google.com> Nov 8, 2022 01:25AM

Accepted by cl...@google.com.

ap...@google.com <ap...@google.com> #8Dec 1, 2022 09:33PM

The following release(s) address this bug.It is possible this bug has only been partially addressed:

androidx.navigation:navigation-runtime:2.6.0-alpha08

ap...@google.com <ap...@google.com> #9Dec 14, 2022 07:34PM

Project: platform/frameworks/support
Branch: androidx-main

commit f433d5458950a632900f8a2685ce6eab27272f8c
Author: Clara Fok <clarafok@google.com>
Date: Thu Dec 01 15:52:28 2022

Fix BottomNavView launchSingleTop with NavGraph

NavController previously did not apply launchSingleTop when user repeatedly navigates to the starting destination of a Menu when this starting destination is a NavGraph. This results in the destination being added mulitple times to backstack.

Now NavController checks if the destination is a NavGraph and if so, adds all destinations from the node to its final startDestination (i.e. nested nav graphs) to singleTop.

NavController backstack and Navigator backstacks entries are replaced accordingly upon singleTop navigations.

Test: ./gradlew navigation:navigation-runtime:cC
Bug: 253256629
Relnote: singleTop now works with NavGraph such that if the top destination of the backstack is a NavGraph's startDestination, all destinations starting from original destination to its startDestination will only be added to the top of the backstack once.
Change-Id: Id4bea16aff3dd776826fc6d746475e293eb64b0e

M navigation/navigation-common/src/main/java/androidx/navigation/NavigatorState.kt
M navigation/navigation-runtime/src/androidTest/java/androidx/navigation/NavControllerTest.kt
M navigation/navigation-runtime/src/main/java/androidx/navigation/NavController.kt

https://android-review.googlesource.com/2283419

cl...@google.com <cl...@google.com> #10Dec 14, 2022 07:39PM

Marked as fixed.

This has been fixed internally and will be available in Navigation 2.6.0-alpha05

pr...@google.com <pr...@google.com> #11Feb 8, 2023 06:22PM