P38_a.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:background="#212121"
    tools:context=".FragmentOne">

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginStart="10dp"
        android:padding="10dp"
        android:text="Send"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />

    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginEnd="10dp"
        android:padding="10dp"
        android:text="Clear"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />


    <Button
        android:id="@+id/btnOrange"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginStart="10dp"
        android:padding="10dp"
        android:text="Red Backgroung"
        app:layout_constraintEnd_toStartOf="@id/btnGrey"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/btn1"
        />


    <Button
        android:id="@+id/btnGrey"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end"
        android:layout_marginTop="10dp"
        android:layout_marginEnd="10dp"
        android:padding="10dp"
        android:text="Grey Background"
        app:layout_constraintStart_toEndOf="@id/btnOrange"
        app:layout_constraintTop_toBottomOf="@id/btn2"
        app:layout_constraintEnd_toEndOf="parent"
        />

</androidx.constraintlayout.widget.ConstraintLayout>