Android CardView cardElevation and shadow is not working
<p>I have this set of Cards using CardView inside an activity.</p>

<p>When running the app, I get this not expected cardview : no elevation, no shadow...</p>

<p><strong>Result on Android 7 device :</strong> </p>

<p><a href="https://i.stack.imgur.com/4eXth.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4eXth.png" alt="Android 7"></a></p>

<p>Code</p>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_gravity="center"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    card_view:cardCornerRadius="4dp"
    card_view:cardElevation="4dp"
    card_view:cardUseCompatPadding="true"
    android:layout_margin="8dp"
    android:gravity="center_horizontal"
    android:id="@+id/card_view"
    android:padding="10dp"
    android:layout_centerHorizontal="true"
    card_view:cardBackgroundColor="@color/main_color_grey_800"&gt;

    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:orientation="vertical"&gt;

        &lt;ImageView
            android:id="@+id/image"
            android:layout_width="match_parent"
            android:layout_height="350.0dp"
            android:scaleType="centerCrop"
             /&gt;

        &lt;TextView
            android:id="@+id/title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@android:color/white"
            android:padding="15.0dp"
            android:textColor="@android:color/black"
            android:textSize="16.0sp"
            android:text="@string/LoremText" /&gt;

        &lt;TextView
            android:id="@+id/desc"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@android:color/white"
            android:padding="15.0dp"
            android:textColor="@android:color/black"
            android:textSize="12.0sp"
            android:textAlignment="center"
            android:text="@string/LoremText" /&gt;

        &lt;LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="end"
            android:orientation="horizontal"
            android:paddingTop="10.0dip"&gt;

            &lt;Button
                android:id="@+id/answer_1"
                android:layout_width="0px"
                android:layout_height="50.0dip"
                android:text="@string/Maybe"
                android:textColor="@color/white"
                android:background="@color/cpb_red"
                android:textSize="14sp"
                style="@style/DBTheme.Button.Orange"
                android:textStyle="bold"
                android:layout_weight="1"
                tools:ignore="ButtonStyle"
                android:visibility="gone" /&gt;

            &lt;Button
                android:id="@+id/answer_2"
                style="@style/DBTheme.Button.Orange"
                android:layout_width="0px"
                android:layout_height="50.0dip"
                android:text="@string/yes_button"
                android:textColor="@android:color/white"
                android:textSize="14sp"
                android:textStyle="bold"
                android:background="@color/cpb_red"
                android:layout_weight="1"
                android:visibility="gone" /&gt;
            &lt;Button
                android:id="@+id/answer_3"
                style="@style/DBTheme.Button.Orange"
                android:layout_width="0px"
                android:layout_height="50.0dip"
                android:layout_weight="1.0"
                android:textStyle="bold"
                android:text="@string/no_button"
                android:textColor="@color/white"
                android:background="@color/cpb_red"
                android:textSize="14sp"
                android:visibility="gone" /&gt;
        &lt;/LinearLayout&gt;
    &lt;/LinearLayout&gt;

    &lt;View
        android:layout_width="match_parent"
        android:layout_height="4.0dp"
        android:background="@drawable/shadow" /&gt;
&lt;/android.support.v7.widget.CardView&gt;
</code></pre>

<p>Any ideas on how to solve this ? Thanks :)</p>