Quelle  camerax_fragment_camera.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"
    android:id="@+id/camera_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/black"
    android:fitsSystemWindows="false">

    <androidx.camera.view.PreviewView
        android:id="@+id/camera_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="false"
        app:scaleType="fitCenter" />

    <ch.threema.app.camera.TimerView
        android:id="@+id/timer_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="visible"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.google.android.material.progressindicator.CircularProgressIndicator
        android:id="@+id/progress"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:indeterminate="true"
        android:visibility="gone"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>