How can I show the shadow only on the bottom side

问题:

I have this layout :

    <?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>

I have set the elevation and paddingBottom of MyTabs to show the shadow under the tablayout, but in this way the shadown is showed not only on the bottom side but on each side.

I have to show the shadow only on the bottom side, what I have to do ?

OT : this layout is also too slow to be rendered