I can't setText to navigation view menu item after user is logged it. Error : NullPointerException

Question

I'm trying to setText and setDrawable in the NavigationView menuItem after the user is signed in. But after user is signing in i'm getting NullPointerException for the TextView and CircleImageView. Here is the java code and XML for the menu and NavigationView

    @Override
        protected void onStart() {
            super.onStart();
            userAuth.addAuthStateListener(authStateListener);
        }
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        userAuth = FirebaseAuth.getInstance();

        sideMenu = findViewById(R.id.navMenu);

        authStateListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                if(firebaseAuth.getCurrentUser() != null)
                    updateActivity(true);
                else
                    updateActivity(false);
            }
        };

    private void updateActivity(Boolean isActive) {
            CircleImageView circleImageView = (CircleImageView) sideMenu.getMenu().findItem(R.id.profile_image);
            if(isActive)
            {
                Glide.with(Home.this)
                        .load(Objects.requireNonNull(userAuth.getCurrentUser()).getPhotoUrl())
                        .centerCrop()
                        .into(circleImageView);
                ((TextView)findViewById(R.id.navName)).setText(userAuth.getCurrentUser().getDisplayName());
                sideMenu.getMenu().findItem(R.id.logout).setVisible(true);
                sideMenu.getMenu().findItem(R.id.login).setVisible(false);
            }else
            {
                Glide.with(Home.this)
                        .load(R.drawable.splash_logo)
                        .centerCrop()
                        .into(circleImageView);
                ((TextView)findViewById(R.id.navName)).setText(R.string.app_name);
                sideMenu.getMenu().findItem(R.id.logout).setVisible(false);
                sideMenu.getMenu().findItem(R.id.login).setVisible(true);
            }

        }

This is the menu (home.xml)

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <group
        android:id="@+id/main"
        android:checkableBehavior="single">
        <item
            android:id="@+id/login"
            android:title="Login" />
    </group>

    <group
        android:id="@+id/second"
        android:checkableBehavior="single">
        <item
            android:id="@+id/share"
            android:title="Share" />
        <item
            android:id="@+id/report"
            android:title="Report" />
    </group>

    <group
        android:id="@+id/third"
        android:checkableBehavior="single">
        <item
            android:id="@+id/license"
            android:title="Licenses"/>
        <item
            android:id="@+id/developer"
            android:title="Developer" />
        <item
            android:id="@+id/contact"
            android:title="Contact us" />

        <item
            android:id="@+id/logout"
            android:title="Logout"
            android:visible="false" />
    </group>

</menu>

This is NavigationView in activity.xml

<com.google.android.material.navigation.NavigationView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:headerLayout="@layout/navigation_header"
        app:menu="@menu/home"
        android:id="@+id/navMenu"/>

navigation_header.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorPrimaryDark"
    android:orientation="vertical">


    <de.hdodenhof.circleimageview.CircleImageView
        android:id="@+id/profile_image"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="25dp"
        app:civ_border_color="#ffffff"
        app:civ_border_width="2dp"
        android:src="@color/colorPrimary"/>

    <TextView
        android:id="@+id/navName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/profile_image"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="25dp"
        android:layout_marginBottom="10dp"
        android:fontFamily="@font/montserrat_bold"
        android:text="User Name"
        android:textAlignment="center"
        android:textColor="@android:color/white"
        android:textSize="25sp" />

</RelativeLayout>

Answer 1

First try to get headerView from NavigationView and then get your CircleImageView and TextView like below:

View headerView = sideMenu.getHeaderView(0);
CircleImageView circleImageView = (CircleImageView) headerView.findViewById(R.id.profile_image);
TextView navName = (TextView) headerView.findViewById(R.id.navName);

Complete solution:

private void updateActivity(Boolean isActive) {

    View headerView = sideMenu.getHeaderView(0);

    CircleImageView circleImageView = headerView.findViewById(R.id.profile_image);
    TextView navName = headerView.findViewById(R.id.navName);

    if(isActive) {
        Glide.with(Home.this)
            .load(Objects.requireNonNull(userAuth.getCurrentUser()).getPhotoUrl())
            .centerCrop()
            .into(circleImageView);

        navName.setText(userAuth.getCurrentUser().getDisplayName());
        sideMenu.getMenu().findItem(R.id.logout).setVisible(true);
        sideMenu.getMenu().findItem(R.id.login).setVisible(false);
    } else {
        Glide.with(Home.this)
            .load(R.drawable.splash_logo)
            .centerCrop()
            .into(circleImageView);
        navName.setText(R.string.app_name);
        sideMenu.getMenu().findItem(R.id.logout).setVisible(false);
        sideMenu.getMenu().findItem(R.id.login).setVisible(true);
    }
}