PreferenceScreen always shows with additional space to top

Question

Currently, I'm facing a problem regarding the display of the preference fragment. I'm using a bottom navigation menu and I want to show a toolbar (previously action bar) showing the currently selected menu item of the navigation bar.

The problem is that there seems to be a second invisible toolbar between the wanted toolbar and the top of the preference fragment as seen in the image.

The top of the preference screen:

<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android">

    <PreferenceCategory android:title="@string/preferences_category_online_area">
        <EditTextPreference
            android:key="preference_username"
            android:inputType="text"
            android:persistent="true"
            android:selectAllOnFocus="true"
            android:singleLine="true"
            android:summary="@string/edit_text_preferences_username_summary"
            android:title="@string/edit_text_preferences_username_text" />
        <EditTextPreference
            android:key="preference_password"
            android:inputType="textPassword"
            android:persistent="true"
            android:selectAllOnFocus="true"
            android:singleLine="true"
            android:summary="@string/edit_text_preferences_passwort_summary"
            android:title="@string/edit_text_preferences_passwort_text" />
...

The mobile_navigation.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/mobile_navigation"
    app:startDestination="@+id/navigation_library">

    <fragment
        android:id="@+id/navigation_dummy"
        android:name="de.example.OnlineSelectionFragment"
        android:label="@string/title_dummy"
        tools:layout="@layout/fragment_dummy" />

    <fragment
        android:id="@+id/navigation_preferences"
        android:name="de.example.PrefsFragment"
        android:label="@string/title_preferences" />
</navigation>

Class PrefsFragment.kt in which the fragment is populated with the preferences

package de.example

import android.os.Bundle
import androidx.preference.PreferenceFragmentCompat


class PrefsFragment : PreferenceFragmentCompat() {

    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
        setPreferencesFromResource(R.xml.preferences, null)
    }
}

How can I remove the empty top space? Previously, the PrefsFragment has been shown within an extra activity but without it I cannot format it in XML.

Thank you very much!

Edit 1 As requested the main activity xml file:

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">

    <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_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="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.constraintlayout.widget.ConstraintLayout>

Answer 1

Problem has been solved.

The reason for the behaviour was the android:paddingTop="?attr/actionBarSize" in the main activity xml file.