How to save Fragment state in Android Navigation Component

In this android programming source code example, we are going to save Fragment state in Android Navigation Component

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

Below is a step by step source code to save Fragment state in Android Navigation Component

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=".BluetoothAndNavigation.BluetoothAndNavigationActivity17">

    <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_graph7"/>

</androidx.constraintlayout.widget.ConstraintLayout>

res/navigation/nav_graph7.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_graph7"
    app:startDestination="@id/navFragment17">

    <fragment
        android:id="@+id/navFragment17"        android:name="com.bluapp.androidview2.BluetoothAndNavigation.NavFragment17"
        android:label="fragment_nav_fragment17"
        tools:layout="@layout/fragment_nav_fragment17" />
</navigation>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class BluetoothAndNavigationActivity17 extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bluetooth_and_navigation17);
    }
}

fragment_nav_fragment17.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=".BluetoothAndNavigation.NavFragment17">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:text="Save and restore fragment state"/>

</androidx.constraintlayout.widget.ConstraintLayout>

NavFragment17.java

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

public class NavFragment17 extends Fragment {
    private String name;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_nav_fragment17, container, false);
        return rootView;
    }

    @Override
    public void onSaveInstanceState(Bundle state){
        super.onSaveInstanceState(state);
        if(state!=null){
            state.putString("website","Inducesmile");
            Toast.makeText(getActivity(),"Fragment Save State",Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void onViewStateRestored(@Nullable Bundle savedInstanceState){
        super.onViewStateRestored(savedInstanceState);
        if(savedInstanceState!=null){
            String website = savedInstanceState.getString("website");
            Toast.makeText(getActivity(),"Fragment Restore State: "+website,Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState){
        super.onActivityCreated(savedInstanceState);
    }


}

app/build.gradle

implementation 'androidx.navigation:navigation-fragment:2.1.0-alpha06'
implementation 'androidx.navigation:navigation-ui:2.1.0-alpha06'

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