title: button change drawable on holding
body: <p>I'm trying to make this volume button that changes the drawable according to the state that it is put in. So on default the Volume of the device will be on, when pressed it will mute the device, and when its held it'll change the device to vibrating only. Now I am trying to change the drawable of when its put on vibrating, but nothing I try seems to work. I currently have this code in my XML, and I tried playing around with the pressed state but I couldn't get something to work that changes the drawable accordingly.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
      &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;item android:drawable="@drawable/ic_volume_down_black_24dp"
      android:state_checked="true" /&gt;
  
      &lt;item android:drawable="@drawable/ic_volume_off_black_24dp"
      android:state_checked="false"/&gt;    
  &lt;/selector&gt;
  </code></pre>