title: Error: 'F' is not a valid file-based resource name character: File-based resource names must contain only lowercase a-z, 0-9, or underscore
body: <p><strong>Error:</strong> </p>
  
  <p><code>'F' is not a valid file-based resource name character: File-based resource names must contain only lowercase a-z, 0-9, or underscore</code></p>
  
  <pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;set xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  &lt;alpha
      android:duration="2000"
      android:fromAlpha="0.0"
      android:toAlpha="1.0"
      android:interpolator="@android:anim/accelerate_interpolator" /&gt;
  &lt;/set&gt;
  </code></pre>
  
  <p>Where is the mistake? I do not see</p>