I am developing an application in Android Studio with Kotlin. I have a page called InicioActivity with a navbar. I want the content of the current page to be hidden and the content of the new page to be shown when an item in the navbar is clicked. With my current code, I can only hide the content of the page I’m on, but I can’t show the content of the new page.

Here is my InicioActivity.kt:

class InicioActivity : AppCompatActivity() {
    private lateinit var principianteBoton: Button
    private lateinit var intermedioBoton: Button
    private lateinit var avanzadoBoton: Button
    private lateinit var textView: TextView
    private lateinit var imagenPrincipiante: ImageView
    private lateinit var imagenIntermedio: ImageView
    private lateinit var imagenAvanzado: ImageView
    private lateinit var binding: InicioBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = InicioBinding.inflate(layoutInflater)
        setContentView(binding.root)

        setSupportActionBar(binding.toolbar) // Configure the Toolbar as ActionBar

        val navView: BottomNavigationView = binding.navView

        val navController = findNavController(R.id.nav_host_fragment_activity_main)
        val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications
            )
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
        principianteBoton = findViewById(R.id.botonPrincipiante)
        intermedioBoton = findViewById(R.id.botonIntermedio)
        avanzadoBoton = findViewById(R.id.botonAvanzado)
        textView = findViewById(R.id.textView)
        imagenPrincipiante = findViewById(R.id.imagenPrincipiante)
        imagenIntermedio = findViewById(R.id.imagenIntermedio)
        imagenAvanzado = findViewById(R.id.imagenAvanzado)

        principianteBoton.setOnClickListener {
            Toast.makeText(this, "Nivel principiante activado.", Toast.LENGTH_SHORT).show()
        }
        intermedioBoton.setOnClickListener {
            Toast.makeText(this, "Nivel intermedio activado.", Toast.LENGTH_SHORT).show()
        }
        avanzadoBoton.setOnClickListener {
            Toast.makeText(this, "Nivel avanzado activado.", Toast.LENGTH_SHORT).show()
        }
        navView.setOnNavigationItemSelectedListener { item ->
            when (item.itemId) {
                R.id.navigation_dashboard, R.id.navigation_notifications -> {
                    // Hide the elements when a navigation item is selected
                    textView.visibility = View.GONE
                    imagenPrincipiante.visibility = View.GONE
                    imagenIntermedio.visibility = View.GONE
                    imagenAvanzado.visibility = View.GONE
                    principianteBoton.visibility = View.GONE
                    intermedioBoton.visibility = View.GONE
                    avanzadoBoton.visibility = View.GONE
                    true
                }
                else -> false
            }
        }
    }
}

This is the XML linked to InicioActivity:

<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/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:text="@string/bienvenido"
        app:layout_constraintBottom_toTopOf="@id/imagenPrincipiante"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.1" />

    <ImageView
        android:id="@+id/imagenPrincipiante"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginTop="96dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/textView"
        app:srcCompat="@drawable/principiante" />

    <Button
        android:id="@+id/botonPrincipiante"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="PRINCIPIANTE"
        app:layout_constraintTop_toBottomOf="@id/imagenPrincipiante"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintVertical_bias="0.3" />

    <ImageView
        android:id="@+id/imagenIntermedio"
        android:layout_width="100dp"
        android:layout_height="100dp"
        app:srcCompat="@drawable/intermedio"
        app:layout_constraintTop_toBottomOf="@id/botonPrincipiante"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintVertical_bias="0.4" />

    <Button
        android:id="@+id/botonIntermedio"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="INTERMEDIO"
        app:layout_constraintTop_toBottomOf="@id/imagenIntermedio"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintVertical_bias="0.5" />

    <ImageView
        android:id="@+id/imagenAvanzado"
        android:layout_width="100dp"
        android:layout_height="100dp"
        app:srcCompat="@drawable/avanzado"
        app:layout_constraintTop_toBottomOf="@id/botonIntermedio"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintVertical_bias="0.6" />

    <Button
        android:id="@+id/botonAvanzado"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="AVANZADO"
        app:layout_constraintTop_toBottomOf="@id/imagenAvanzado"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintVertical_bias="0.7" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:menu="@menu/bottom_nav_menu" />

    <fragment
        android:id="@+id/nav_host_fragment_activity_main"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@id/nav_view"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/mobile_navigation" />

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:titleTextColor="@android:color/white"
        tools:ignore="MissingConstraints" />
</androidx.constraintlayout.widget.ConstraintLayout>

have tried hiding the objects from the fragment class, but it did not work. I have also tried using a method called onSupportNavigateUp, but it did not work either. Additionally, I tried using onNavigationItemSelected in this way, but it wouldn’t hide anything:

 override fun onNavigationItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.navigation_dashboard -> {
            Log.d("NAV", "Dashboard selected")
            // Hide the elements when a navigation item is selected
            textView.visibility = View.GONE
            imagenPrincipiante.visibility = View.GONE
            imagenIntermedio.visibility = View.GONE
            imagenAvanzado.visibility = View.GONE
            principianteBoton.visibility = View.GONE
            intermedioBoton.visibility = View.GONE
            avanzadoBoton.visibility = View.GONE
            return true
        }
        R.id.navigation_notifications -> {
            Log.d("NAV", "Notifications selected")
            textView.visibility = View.GONE
            imagenPrincipiante.visibility = View.GONE
            imagenIntermedio.visibility = View.GONE
            imagenAvanzado.visibility = View.GONE
            principianteBoton.visibility = View.GONE
            intermedioBoton.visibility = View.GONE
            avanzadoBoton.visibility = View.GONE
            return true
        }
    }
    return false
}