title: Android - spotShadowAlpha only for linearlayout
body: <p>I am using the elevation attribute for my linearlayout, but the shadow is to bright. I need a darker shadow only for the linear layout.</p>
  
  <p>I added <code>android:spotShadowAlpha</code> to my <code>styles.xml</code>. It worked, but not only for the linear layout. Every View has a darker shadow.</p>
  
  <p>Styles.xml</p>
  
  <pre><code>&lt;resources&gt;
      &lt;!-- Base application theme. --&gt;
      &lt;style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"&gt;
          &lt;!-- Customize your theme here. --&gt;
          &lt;item name="android:ambientShadowAlpha"&gt;0&lt;/item&gt;
          &lt;item name="android:spotShadowAlpha"&gt;0.55   &lt;/item&gt;
          &lt;item name="colorPrimary"&gt;@color/colorPrimary&lt;/item&gt;
          &lt;item name="colorPrimaryDark"&gt;@color/colorPrimaryDark&lt;/item&gt;
          &lt;item name="colorAccent"&gt;@color/colorAccent&lt;/item&gt;
      &lt;/style&gt;
  &lt;/resources&gt;
  </code></pre>
  
  <p>linearlayout in <code>activity_main.xml</code></p>
  
  <pre><code>&lt;LinearLayout
          android:id="@+id/linl"
          android:layout_width="250dp"
          android:layout_height="250dp"
          android:layout_marginStart="55dp"
          android:layout_marginTop="208dp"
          android:layout_marginEnd="56dp"
          android:layout_marginBottom="209dp"
          android:background="@drawable/custom_buttom"
          android:elevation="70dp"
          android:orientation="horizontal"
  
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toTopOf="parent"&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Background <code>@drawable/custom_buttom</code></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"&gt;
      &lt;solid android:color="#FFFFFF"/&gt;
      &lt;corners android:radius="999dp"/&gt;
  &lt;/shape&gt;
  </code></pre>