Navigation Component: Cannot find NavController

Question

I am using Navigation Component for navigating in my app. It works fine inside fragments but it fails to find the nav host in the activity that holds the actual navigation host.

I am trying to open a new fragment when the user clicks on FAB, which I included in Main activity's XML. When I call findNavController() it fails to find the controller. The nav host controller is in the XML layout. I can't understand why it fails to find it.

MainActivity

class MainActivity : AppCompatActivity(), OnActivityComponentRequest {     override fun getTabLayout(): TabLayout {         return this.tabLayout     }      override fun getFap(): FloatingActionButton {         return this.floatingActionButton     }      private lateinit var tabLayout: TabLayout     private lateinit var floatingActionButton: FloatingActionButton      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         setContentView(R.layout.activity_main)         setSupportActionBar(toolbar)         this.tabLayout = tabs         this.floatingActionButton = fab          fab.setOnClickListener {           it.findNavController().navigate(R.id.addNewWorkoutFragment)          }     } } 

Activity main XML

<?xml version="1.0" encoding="utf-8"?> <androidx.coordinatorlayout.widget.CoordinatorLayout         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:layout_width="match_parent"         android:layout_height="match_parent"         tools:context=".domain.MainActivity"         android:animateLayoutChanges="true">      <com.google.android.material.appbar.AppBarLayout             android:layout_height="wrap_content"             android:layout_width="match_parent"             android:theme="@style/AppTheme.AppBarOverlay">          <androidx.appcompat.widget.Toolbar                 android:id="@+id/toolbar"                 android:layout_width="match_parent"                 android:layout_height="?attr/actionBarSize"                 android:background="?attr/colorPrimary"                 app:layout_scrollFlags="scroll|enterAlways"                 app:popupTheme="@style/AppTheme.PopupOverlay"/>          <com.google.android.material.tabs.TabLayout                 android:id="@+id/tabs"                 android:layout_width="match_parent"                 android:layout_height="wrap_content">              <com.google.android.material.tabs.TabItem                     android:text="Test 1"                     android:layout_height="match_parent"                     android:layout_width="match_parent"/>              <com.google.android.material.tabs.TabItem                     android:text="Test 2"                     android:layout_height="match_parent"                     android:layout_width="match_parent"/>         </com.google.android.material.tabs.TabLayout>      </com.google.android.material.appbar.AppBarLayout>        <fragment         android:id="@+id/nav_host_fragment"         android:name="androidx.navigation.fragment.NavHostFragment"         android:layout_width="match_parent"         android:layout_height="match_parent"         app:defaultNavHost="true"         app:navGraph="@navigation/main_navigation" />       <com.google.android.material.bottomappbar.BottomAppBar             android:id="@+id/bar"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:layout_gravity="bottom"/>       <com.google.android.material.floatingactionbutton.FloatingActionButton             android:id="@+id/fab"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             app:layout_anchorGravity="right|top"             app:layout_anchor="@+id/bar"             android:src="@drawable/ic_add_black_24dp"/>  </androidx.coordinatorlayout.widget.CoordinatorLayout> 

Answer 1

I was getting the same exeception until I managed to get the navController this way:

val navHostFragment = supportFragmentManager.findFragmentById(R.id.my_fragment_container_view_id) as NavHostFragment val navController = navHostFragment.navController 

Obtained from this answer:

Before finding the nav controller, you need to set the view, if you are using binding:

binding = BaseLayoutBinding.inflate(layoutInflater) val view = binding.root setContentView(view) 

If not:

setContentView(R.layout.activity_main) 

Use the corresponding binding for fragments.