MainActivity.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=".MainActivity">

    <TextView
        android:id="@+id/mainscreen_title"
        android:layout_width="221dp"
        android:layout_height="49dp"
        android:layout_marginStart="92dp"
        android:layout_marginTop="32dp"
        android:text="@string/enter_number"
        android:textSize="24sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/input_left"
        android:layout_width="150dp"
        android:layout_height="44dp"
        android:layout_marginStart="136dp"
        android:layout_marginTop="32dp"
        android:ems="10"
        android:hint="@string/enter_number"
        android:inputType="number"
        android:numeric="signed|integer|decimal"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/mainscreen_title" />

    <Button
        android:id="@+id/addition_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="96dp"
        android:layout_marginTop="32dp"
        android:text="@string/Addition"
        android:textSize="24sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/input_left" />

    <Button
        android:id="@+id/subtraction_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="96dp"
        android:layout_marginTop="48dp"
        android:text="@string/Subtraction"
        android:textSize="24sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/addition_button" />

    <Button
        android:id="@+id/division_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="84dp"
        android:text="@string/Division"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/input_left" />

    <Button
        android:id="@+id/multiplication_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="48dp"
        android:layout_marginEnd="84dp"
        android:text="@string/Multiply"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/division_button" />

    <Button
        android:id="@+id/calculate_button"
        android:layout_width="135dp"
        android:layout_height="46dp"
        android:layout_marginStart="48dp"
        android:layout_marginTop="64dp"
        android:text="@string/calculate"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/subtraction_button" />

    <TextView
        android:id="@+id/output"
        android:layout_width="307dp"
        android:layout_height="39dp"
        android:layout_marginStart="48dp"
        android:layout_marginTop="44dp"
        android:text="@string/output"
        android:textSize="24sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/clear_button" />

    <TextView
        android:id="@+id/calculate_log"
        android:layout_width="354dp"
        android:layout_height="67dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="28dp"
        android:autoText="true"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/output" />

    <Button
        android:id="@+id/clear_button"
        android:layout_width="135dp"
        android:layout_height="46dp"
        android:layout_marginTop="64dp"
        android:layout_marginEnd="36dp"
        android:text="@string/clear"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/multiplication_button" />


</androidx.constraintlayout.widget.ConstraintLayout>