How to create a nested graph with Android Component Navigation in Kotlin

In this android kotlin source code example, we are going to create a nested graph with Android Component Navigation in Kotlin.

You can copy and adopt this source code example to your Kotlin android project without reinventing the wheel.

Below is a step by step source code to create a nested graph with Android Component Navigation in Kotlin.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".Navigation.NavigationActivity12">

    <fragment
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph12"/>


</androidx.constraintlayout.widget.ConstraintLayout>

navigation/nav_graph12.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_graph12"
    app:startDestination="@id/navFragment12">

    <fragment
        android:id="@+id/navFragment12"
        android:name="com.bluapp.kotlinview.Navigation.NavFragment12"
        android:label="@string/app_name"
        tools:layout="@layout/fragment_nav_fragment12">
        <action
            android:id="@+id/navFragment12tonav_graph121"
            app:destination="@id/nav_graph121"/>
    </fragment>

    <navigation
        android:id="@+id/nav_graph121"
        app:startDestination="@id/navFragment121">

        <fragment
            android:id="@+id/navFragment121"
            android:name="com.bluapp.kotlinview.Navigation.NavFragment121"
            android:label="@string/app_name"
            tools:layout="@layout/fragment_nav_fragment121">
        <action
            android:id="@+id/navFragment121tonavFragment122"
            app:destination="@id/navFragment122"/>
        </fragment>

        <fragment
            android:id="@+id/navFragment122"
            android:name="com.bluapp.kotlinview.Navigation.NavFragment"
            android:label="@string/app_name"
            tools:layout="@layout/fragment_nav" />
    </navigation>

</navigation>

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.bluapp.kotlinview.R

class NavigationActivity12 : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_navigation12)
    }
}

fragment_nav_fragment12.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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/constraintlayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Navigation.NavFragment12">

    <androidx.appcompat.widget.AppCompatButton
        android:id="@+id/startBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start Nested Graph"
        android:background="@color/colorAccent"
        android:textColor="#ffffff"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

NavFragment12.kt

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.appcompat.widget.AppCompatButton
import androidx.navigation.Navigation

import com.bluapp.kotlinview.R

class NavFragment12 : Fragment() {
    private var startBtn: AppCompatButton? = null

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_nav_fragment12, container, false)
        startBtn = view.findViewById(R.id.startBtn) as AppCompatButton
        startBtn!!.setOnClickListener {
            Navigation.findNavController(view).navigate(R.id.navFragment12tonav_graph121);
        }
        return view
    }



}

fragment_nav_fragment121.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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/constraintlayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Navigation.NavFragment121">

    <androidx.appcompat.widget.AppCompatButton
        android:id="@+id/startBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start Fragment"
        android:background="@color/colorAccent"
        android:textColor="#ffffff"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

NavFragment121.kt

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.appcompat.widget.AppCompatButton
import androidx.navigation.Navigation

import com.bluapp.kotlinview.R

class NavFragment121 : Fragment() {
    private var startBtn: AppCompatButton? = null
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_nav_fragment121, container, false)
        startBtn = view.findViewById(R.id.startBtn) as AppCompatButton
        startBtn!!.setOnClickListener {
            Navigation.findNavController(view).navigate(R.id.navFragment121tonavFragment122);
        }
        return view
    }


}

fragment_nav.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".Navigation.NavFragment">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="NavFragment"
        android:textSize="20sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>


</androidx.constraintlayout.widget.ConstraintLayout>

NavFragment.kt

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup

import com.bluapp.kotlinview.R


class NavFragment : Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_nav, container, false)
    }

}

app/build.gradle

    implementation 'androidx.navigation:navigation-fragment:2.1.0'
    implementation 'androidx.navigation:navigation-ui:2.1.0'
    implementation 'androidx.navigation:navigation-fragment-ktx:2.1.0'
    implementation 'androidx.navigation:navigation-ui-ktx:2.1.0'

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