I followed the instructions of writing a transparent layout.

My res/values/style.xml looks like this:

<resources>

  <style name="Theme" parent="android:Theme" />

  <style name="Theme.Transparent">
      <item name="android:windowBackground">@drawable/transparent_background</item>
  </style>

  <drawable name="transparent_background">#00000000</drawable>

</resources>

The activity snippet looks like this:

<activity android:name=".Controlls"
              android:label="Controlls"
              android:theme="@style/Theme.Transparent">

When I start this activity from my root activity, the layout gets drawn correctly, but the background stays black.