title: Drawable selector with same image but different opacity
body: <p>I want to save app space with next idea. But I'm not sure if it possible.</p>
  
  <p>I want to have selector:</p>
  
  <pre><code>&lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
    &lt;item android:drawable="@drawable/arrow_forward" android:state_enabled="true" /&gt;
    &lt;item android:drawable="@drawable/arrow_forward_disabled" android:state_enabled="false"/&gt;
  &lt;/selector&gt;
  </code></pre>
  
  <p>Where <code>arrow_forward</code> is png image and <code>arrow_forward_disabled</code> is same image but with 70% opacity. I've tried to achieve it with <code>layer-list</code> drawable but without success. Is there solution?</p>