title: Android: Custom Horizontal Progress Bar Animation
body: <p>I'm trying to create a progress bar where the bar itself animates in a vertical spin as it progresses horizontally. I'm successfully using my progress drawable as the drawable via:</p>
  
  <pre><code>&lt;ProgressBar
          android:id="@+id/progressBar"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          style="@android:style/Widget.ProgressBar.Horizontal"
          android:progressDrawable="@drawable/custom_progress"
          android:layout_marginRight="5dp" /&gt;
  </code></pre>
  
  <p>Here is my drawable:</p>
  
  <p><img src="https://i.stack.imgur.com/hhGPO.png" alt="enter image description here"></p>
  
  <p>But I want it to have a subtle roll effect as its progressing. So it would look like the vertical lines are moving backwards sorta. You follow? Any help is much appreciated. Thanks.</p>
  
  <p>EDIT:
  I tried created an animation-list as my progress drawable but I'm still not able to see the animation.  Can an animation-list be inside of a clip for the progress item?</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 android:id="@android:id/background" android:drawable="@drawable/gutter"&gt;&lt;/item&gt;
  
  &lt;item android:id="@android:id/progress"&gt;
  
  &lt;clip&gt;
      &lt;animation-list android:oneshot="false"&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate2" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate3" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate4" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate5" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate6" android:duration="100" /&gt;
          &lt;item android:drawable="@drawable/progress_bar_animate7" android:duration="100" /&gt;
      &lt;/animation-list&gt;
  &lt;/clip&gt;
  
  &lt;/item&gt;
  &lt;/layer-list&gt;
  </code></pre>