如何仅在布局的底部显示阴影？

Question

我有这样的布局：

    <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="match_parent"
    android:background="#ffffff"
    android:clickable="true"
    android:focusable="true">


    <android.support.constraint.ConstraintLayout
        android:id="@+id/details"
        android:layout_width="500dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="32dp"
        android:background="@color/grayEB"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/shutdownButton"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.007">

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:text="Flusso autorizzativo"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/textView3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:text="--"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/textView2" />

        <TextView
            android:id="@+id/textView4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginEnd="8dp"
            android:text="Totale cliente"
            app:layout_constraintBaseline_toBaselineOf="@+id/textView2"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.274"
            app:layout_constraintStart_toEndOf="@+id/textView2" />

        <TextView
            android:id="@+id/textView5"
            android:layout_width="wrap_content"
            android:layout_height="15dp"
            android:layout_marginStart="8dp"
            android:layout_marginTop="12dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:text="Spesa PRE: € --"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/textView6"
            app:layout_constraintHorizontal_bias="0.959"
            app:layout_constraintStart_toEndOf="@+id/textView3"
            app:layout_constraintTop_toBottomOf="@+id/textView4"
            app:layout_constraintVertical_bias="0.0" />

        <TextView
            android:id="@+id/textView6"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="60dp"
            android:text="Spesa stimata: € --"
            app:layout_constraintBaseline_toBaselineOf="@+id/textView5"
            app:layout_constraintEnd_toEndOf="parent" />
    </android.support.constraint.ConstraintLayout>

    <Button
        android:id="@+id/shutdownButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="8dp"
        android:text="ShutDown !!!"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <android.support.v4.view.ViewPager
        android:id="@+id/frameLayout2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/MyTabs">

    </android.support.v4.view.ViewPager>

    <android.support.design.widget.TabLayout
        android:id="@+id/MyTabs"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:padding="0dp"
        android:elevation="4dp"
        android:paddingBottom="4dp"
        app:tabGravity="center"
        app:tabMode="scrollable"
        app:layout_constraintBottom_toTopOf="@+id/frameLayout2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/details"
        app:layout_constraintVertical_chainStyle="packed"
        android:background="#ffff"/>




</android.support.constraint.ConstraintLayout>

我已经设置了MyTabs的仰角和paddingBottom以在TabLayout下方显示阴影，但是通过这种方式，不仅在底部而且在每侧都显示阴影。

我必须只在底部显示阴影，我该怎么做？

OT：此布局也太慢而无法呈现