title: Setting transparent background for activity shown as dialog on xml not working on all devices
body: <p>I have a custom view on an activity that is showed as a dialog.
  I applied a custom theme to my activity so its parent is: "@android:style/Theme.Dialog" and I changed the window background to be transparent.</p>
  
  <p>My Manifest.xml:</p>
  
  <pre><code>&lt;activity android:name="com.rev.revcorder.ui.UserAuthenticationDialogActivity" android:screenOrientation="portrait"
              android:theme="@style/userAuthenticationDialog"&gt;
  &lt;/activity&gt;
  </code></pre>
  
  <p>My styles.xml:</p>
  
  <pre><code>&lt;style name="userAuthenticationDialog" parent="@android:style/Theme.Dialog"&gt;
      &lt;item name="android:windowBackground"&gt;@android:color/transparent&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>The issue is that it is working fine on my device (Nexus 4 running 4.4) but on other device that is the same as mine (Nexus 4 running 4.4) it is not. Instead, the background is shown in black not transparent. </p>
  
  <p>It only worked when I set it grammatically by adding:</p>
  
  <pre><code>getWindow().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#00000000")));
  </code></pre>
  
  <p>My question is, what is the difference between setting the window background on my xml style and doing i grammatically ?
  Also, how come it is working on my device and not on another same device ?</p>
  
  <p>Thanks for your help</p>