Android Navigation component: No NavHostFragments found error

Question

I am currently implementing the Navigation Component into my app but it seems finding the NavHostFragment just doesn't work no matter what I do.

I have tried, rebuilding, invalidating, and restarting, changing the names around, and updating my Android Studio but nothing seems to work. I think this is also the reason why I get an error when trying to get the NavController in my MainActivity.kt file as it returns null.

Android Studio version 4.0.1

nav_graph.xml image:

nav_graph.xml

<?xml version="1.0" encoding="utf-8"?>
<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/nav_graph"
    app:startDestination="@id/mainFragment">

    <fragment
        android:id="@+id/mainFragment"
        android:name="com.example.movieapp.ui.main.MainFragment"
        android:label="MainFragment">
        <action
            android:id="@+id/action_mainFragment_to_searchMovieFragment"
            app:destination="@id/searchMovieFragment" />
    </fragment>
    <fragment
        android:id="@+id/searchMovieFragment"
        android:name="com.example.movieapp.ui.search.SearchMovieFragment"
        android:label="SearchMovieFragment" />
</navigation>

main_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.MainActivity">

    <include
        layout="@layout/appbar" />

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var toolbar: Toolbar
    private val navController by lazy {
        (supportFragmentManager.findFragmentById(R.id.main_fragment) as NavHostFragment).navController
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)
        toolbar = findViewById(R.id.mainToolBar)
        setSupportActionBar(toolbar)
        setupActionBarWithNavController(navController)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val inflater: MenuInflater = menuInflater
        inflater.inflate(R.menu.main_menu_bar, menu)
        return true
    }
}

build.gradle (:app)

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.3"

    defaultConfig {
        applicationId "com.example.app"
        minSdkVersion 23
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        debug {}

        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }

        dataBinding {
            enabled true
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    // Retrofit Libraries
    implementation 'com.squareup.retrofit2:retrofit:2.6.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.6.0'

    // Picasso Library
    implementation 'com.squareup.picasso:picasso:2.71828'
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.0'
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

    // Navigation libraries
    def nav_version = "2.3.0"
    implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
    implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
}

Answer 1

The way I was able to resolve the issue was by going to the Activity.xml and changing the fragment class/component tag from androidx.fragment.app.FragmentContainerView to just fragment. It then showed up in the hosts panel of the navigation graph.

Answer 2

I had the same issue and I solved this by creating the NavHostFragment from the Design, Palette and then assign the respective navigation resource file.

Answer 3

As mentioned in Doc, You can also use the Layout Editor to add a NavHostFragment.

1. In your list of project files, double-click on your activity's layout XML file to open it in the Layout Editor.
2. Within the Palette pane, choose the Containers category, or alternatively search for "NavHostFragment".
3. Drag the NavHostFragment view onto your activity.
4. Next, in the Navigation Graphs dialog that appears, choose the corresponding navigation graph to associate with this NavHostFragment, and then click OK.

YOU MAY NEED TO RESTART THE ANDROID STUDIO AFTER THIS (not mentioned in the doc)

Also, you may see "fragment" instead of "FragmentContainerView" when you try to add fragment using above method.

Answer 4

You can find NavController in activity as:

class MainActivity : AppCompatActivity() {

    private lateinit var toolbar: Toolbar
    private lateinit var navController: NavController

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)
        toolbar = findViewById(R.id.mainToolBar)
        setSupportActionBar(toolbar)
        navController = findNavController(R.id.nav_host_fragment)
        setupActionBarWithNavController(navController)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val inflater: MenuInflater = menuInflater
        inflater.inflate(R.menu.main_menu_bar, menu)
        return true
    }
}

Answer 5

For me I added android:name="androidx.navigation.fragment.NavHostFragment" inside FragmentContainerView and worked with me