title: Change shape solid color at runtime inside Drawable xml used as background
body: <p>I've a Drawable xml file (background.xml):</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;layer-list xmlns:android="http://schemas.android.com/apk/res/android" &gt;
      &lt;item&gt;
          &lt;shape&gt;
           ...........
          &lt;/shape&gt;
      &lt;/item&gt;
  
      &lt;item android:id="@+id/shape_id"&gt;
          &lt;shape android:shape="rectangle"&gt;
              &lt;solid android:color="#ffefefef" /&gt; 
          &lt;/shape&gt;
      &lt;/item&gt;
  
  &lt;/layer-list&gt;
  </code></pre>
  
  <p>used by a LinearLayout:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:background="@drawable/background"
      android:id="@+id/layout_id"
      &gt;
  </code></pre>
  
  <p>Now i need to change the shape <code>shape_id</code> solid color at runtime based on some conditions. How to do this?</p>