title: White background on Preference for Tablets
body: <p>I am setting a background for my preference activity, so I wrote a style in styles.xml</p>
  
  <pre><code>&lt;style 
     name="PreferencesTheme" 
     parent="@android:style/Theme.Light.NoTitleBar.Fullscreen"&gt;
     &lt;item name="android:windowBackground"&gt;@drawable/background&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>and in the activity, </p>
  
  <pre><code>  &lt;activity
            android:name="com.phonelight.realparrot.MainActivity"
            android:label="Real Parrot"
            android:screenOrientation="portrait"
            android:theme="@style/PreferencesTheme"&gt;
         &lt;intent-filter&gt;
              &lt;action android:name="android.intent.action.MAIN" /&gt;
              &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
         &lt;/intent-filter&gt;
  
    &lt;/activity&gt;
  </code></pre>
  
  <p>I run this on the emulator for two devices. The first one is a mobile phone, the second is a Tablet.
  <img src="https://i.stack.imgur.com/KUruv.png" alt="mobile phone">
  <img src="https://i.stack.imgur.com/aPm2F.png" alt="Tablet"></p>
  
  <p>Why the background image does not appear on the Tablet. There is only a small margin. I run it on a real Tablet and the whole screen is white too.</p>