Create a layout for RegistrationActivity.kt named activity_registration.xml. Here I have added a UI, so please look at the full version of this file on GitHub. Here is a piece of code from this file:

 <Button android:layout_width="match_parent" android:layout_height="wrap_content"
                        android:text="@string/title_reg"
                        android:id="@+id/reg_submit" android:layout_marginTop="32dp"
                        app:layout_constraintTop_toBottomOf="@+id/country_title_reg"
                        app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="32dp"
                        app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="32dp"/>

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            </android.support.constraint.ConstraintLayout>
        </ScrollView>
    </android.support.v7.widget.CardView>

</android.support.constraint.ConstraintLayout>

Here is the image preview of this layout: