FairEmail/app/src/main/res/layout/dialog_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"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="12dp">

    <RadioGroup
        android:id="@+id/rgTheme"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <RadioButton
            android:id="@+id/rbThemeLight"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/title_setup_light_theme"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium" />

        <RadioButton
            android:id="@+id/rbThemeDark"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:text="@string/title_setup_dark_theme"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium" />

        <RadioButton
            android:id="@+id/rbThemeBlack"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:text="@string/title_setup_black_theme"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium" />

        <RadioButton
            android:id="@+id/rbThemeSystem"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:text="@string/title_setup_system_theme"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium" />
    </RadioGroup>
</androidx.constraintlayout.widget.ConstraintLayout>