kotlin.TypeCastException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment at NavigationExtensionsKt

Question

Exception

I copied the NavigationExtensions.kt extension file from the NavigationAdvancedSample and I get this exception:

Hi Amir, welcome to SO. Please post the actual text of your code and exception, using correct StackOverflow markdown (instead of images). Also have a look at [**how to ask**](https://stackoverflow.com/help/how-to-ask) and [**how to create a minimum, reproducible example**](https://stackoverflow.com/help/minimal-reproducible-example) for better results when using the site. Good luck! — kenny_k, May 04 '20 at 14:33

score 13 · Answer 1 · answered Sep 18 '21 at 15:33

13

In my case, I forgot to add android:name="androidx.navigation.fragment.NavHostFragment" in FragmentContainerView

answered Sep 18 '21 at 15:33

Harshal Pudale

178
1
2
7

2

This was the solution for me too. Thanks! – bqubique Mar 12 '22 at 11:55

tahaak67 · Accepted Answer · 2020-11-12T09:57:30.647

UPDATE: make sure your menu item ids are the same as your navigation resource files ids

also: if you're having a problem with ItemReselectedListener Add null safety checks, your listener should be something like this:

setOnNavigationItemReselectedListener { item ->
        val newlySelectedItemTag = graphIdToTagMap[item.itemId]
        val selectedFragment = fragmentManager.findFragmentByTag(newlySelectedItemTag)
                as NavHostFragment?
        val navController = selectedFragment?.navController
        // Pop the back stack to the start destination of the current navController graph
        navController?.popBackStack(
            navController.graph.startDestination, false
        )
    }

M Saif Ullah · Answer 3 · 2021-03-26T16:02:22.793

5

I also faced this probelem, the solution is actually very simple.

Make sure your menu item's id match the id of NAV_GRAPH not destinations.

I was using the same ids for menu items and destinations, but in this case, menu item should have same id as of NAV_GRAPH.

edited Mar 26 '21 at 16:02

answered Nov 17 '20 at 12:48

M Saif Ullah

86
2
5

score 2 · Answer 4 · answered Mar 11 '22 at 10:37

I manage to solve this problem.

In my case, I was calling val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment before setContentView(binding.root) so I change the order of the methods and everything was Ok.

score 1 · Answer 5 · answered Jun 23 '21 at 07:58

1

I also had the same issue

Check that you have set your start destination and attached it to a fragment. in your nav graph set app:startDestination="@id/your fragment"

this should solve your problem

answered Jun 23 '21 at 07:58

Andrew Ananda

90
1
3

score 0 · Answer 6 · answered Sep 27 '22 at 19:59

So for me it was that inside my navigation graph file the id I declared on

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

Was not the same name as the menu item

<item
        android:id="@+id/my_idd"
        android:enabled="true"
        android:icon="@drawable/icon"
        android:title="@string/test_title" />

Changing the id to be the same for both solved the problem

score 0 · Answer 7 · answered Dec 29 '22 at 08:21

0

I have resolved this, Actually, i set another layout for this activity in setcontentView, When I set the original layout it worked.

answered Dec 29 '22 at 08:21

Jadu

489
3
10

score -1 · Answer 8 · answered May 05 '20 at 07:14

-1

can you try with this?

val selectedFragment: NavHostFragment? = fragmentManager.findFragmentByTag(newlySelectedItemTag) as NavHostFragment

answered May 05 '20 at 07:14

Dimitar

659
7
6

Won't work either cast it to a nullable type or use safe cast operator `as?` – Animesh Sahu May 05 '20 at 08:02
then what will you do if selectedFragment is null? – Dimitar May 05 '20 at 09:41
wrap it with if else – Dimitar May 05 '20 at 09:41
it will throw the same exception if you try to do like this, it won't be able to cast to a non-null `NavHostFragment` type – Animesh Sahu May 05 '20 at 09:44

kotlin.TypeCastException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment at NavigationExtensionsKt

8 Answers8