title: Change background color/drawable from the source
body: <p>I have many XMLs that use background color from <strong>shape drawables</strong> like:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout
      android:background="@drawable/background"
  /&gt;
  </code></pre>
  
  <p>My shape background xml is:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;shape xmlns:android="http://schemas.android.com/apk/res/android"
      android:shape="rectangle"&gt;
      &lt;gradient 
          android:type="linear"
          android:startColor="#FFffffff"
          android:endColor="#FFE8E8E8"
          android:angle="315" /&gt;    
  &lt;/shape&gt;
  </code></pre>
  
  <p>Now I want to add a feature where I give the user the option to change the background color. Is there a quick way that I can change the source shape drawable based on some value instead of going to <strong>Each</strong> activity that loads xml and change that?</p>
  
  <p>Thank you.</p>