title: How to reference a style in a custom theme
body: <p>I have a login screen that is branded differently for different builds of my application. I need the background image to be different in the layout file for this screen, so I want to point to a different style for the top level container. I'm a bit at a loss at how to do this.</p>
  
  <p>I have declared a styleable something like:</p>
  
  <pre><code>&lt;resources&gt;
  
      &lt;declare-styleable name="ThemeBase"&gt;
         &lt;attr name="loginPageContainerStyle" format="reference" /&gt;
      &lt;/declare-styleable&gt;
  
  &lt;/resources&gt;
  </code></pre>
  
  <p>I have several different themes for the application, as such:</p>
  
  <pre><code>&lt;resources&gt;
  
      &lt;style name="ThemeBase" parent="android:style/Theme.Light" /&gt;
  
      &lt;style name="ThemeOne" parent="ThemeBase"&gt;
         &lt;item name="loginPageContainerStyle"&gt;@style/loginPageContainerThemeOne&lt;/item&gt;
      &lt;/style&gt;
  
      &lt;style name="ThemeTwo" parent="ThemeBase"&gt;
         &lt;item name="loginPageContainerStyle"&gt;@style/loginPageContainerThemeTwo&lt;/item&gt;
      &lt;/style&gt;
  
  &lt;/resources&gt;
  </code></pre>
  
  <p>And I have defined the following styles:</p>
  
  <pre><code>&lt;resources&gt;
      &lt;style name="loginPageContainerThemeOne"&gt;
          &lt;item name="android:background"&gt;@drawable/background_theme_one&lt;/item&gt;
      &lt;/style&gt;
  
      &lt;style name="loginPageContainerThemeTwo"&gt;
          &lt;item name="android:background"&gt;@drawable/background_theme_two&lt;/item&gt;
      &lt;/style&gt;
  &lt;/resources&gt;
  </code></pre>
  
  <p>And finally a login.xml file something like:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/loginRoot"
      style= [ ? WHAT GOES HERE ? ]
      android:gravity="center_horizontal"
      android:orientation="horizontal"&gt;
  
      [ LAYOUT STUFF ... ]
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Am I doing anything wrong? Can this be done this way?</p>