pwm/app/src/main/res/layout/activity_theme.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=".ThemeActivity">

    <RadioGroup
        android:id="@+id/themeRadioGroup"
        android:layout_width="156dp"
        android:layout_height="120dp"
        app:layout_constraintBottom_toTopOf="@+id/themeStatus"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <RadioButton
            android:id="@+id/radioButtonDefault"
            android:layout_width="match_parent"
            android:layout_height="40dp" />

        <RadioButton
            android:id="@+id/radioButtonDark"
            android:layout_width="match_parent"
            android:layout_height="40dp" />

        <RadioButton
            android:id="@+id/radioButtonLight"
            android:layout_width="match_parent"
            android:layout_height="40dp" />
    </RadioGroup>

    <TextView
        android:id="@+id/themeStatus"
        android:layout_width="91dp"
        android:layout_height="56dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/themeRadioGroup" />
</androidx.constraintlayout.widget.ConstraintLayout>