title: Android Dark Mode: Elevation Not Changing Surface Color
body: <p>I'm following google's excellent <a href="https://material.io/design/color/dark-theme.html#properties" rel="nofollow noreferrer">blog post</a> to make a dark theme for my app, but I don't see any reference on how I get the elevation effects on my views(buttons, app bar, etc) to work. For example when I set my app theme to 
  <code>&lt;style name="AppTheme" parent="Theme.AppCompat.DayNight.NoActionBar"&gt;</code> 
  and make a button or a card like so:</p>
  
  <pre><code>        &lt;Button
          android:id="@+id/keypadOne"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          android:layout_weight="1"
          android:background="@color/surface"
          android:elevation="01dp"
          android:text="@string/one"
          android:textColor="@color/onSurface"
          android:textSize="36sp" /&gt;
  </code></pre>
  
  <p>I would expect to see the effect that makes the object appear lighter due to the semi-transparent white overlay used in dark themes to imply elevation or being closer to a light source than the background. Instead, my buttons,action bar, etc, are the same color as the background and therefore invisible.</p>
  
  <p>My questions are:</p>
  
  <ol>
  <li>Do I have to implement this elevation functionality manually or is that provided by the Material library?</li>
  <li>If I get this working automatically for Android 10+ will I have to implement a manual solution for backwards compatibility on versions 9 and earlier?</li>
  </ol>