title: Android seekbar set custom style using nine-patch images
body: <p>I am trying to create a custom-styled seekbar.
  I have two nine-patch images one is a gray stretching bar search_progress.9.png (background color) and the other is a green stretching bar search_progress_bar.9.png (foreground color).</p>
  
  <p>I use this xml as my seekbar's progressDrawable:</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/search_progress"&gt;&lt;/item&gt;
      &lt;item android:id="@android:id/progress" android:drawable="@drawable/search_progress_bar"&gt;&lt;/item&gt;
  &lt;/layer-list&gt;
  </code></pre>
  
  <p>My problem is that, instead of the bar filling up to my thumb position, the entire bar is green all the time (search_progress_bar image). How can I get the same effect as Android's progress_horizontal.xml with my own images (I do not want to use shapes to draw my bar)?</p>