How to apply Vertical progress Drawable for a vertical seekbar

Question

I have created a vertical seek bar by adding android:rotation="270" in seekbar. But i have been shared with a progress drawable which is vertical in position. If i am applying this vertical image as progress drawable , seekbar is not looking fine. can someone help me for this ?

layout:

<SeekBar  
    android:id="@+id/seekBar"  
    android:layout_width="match_parent"  
    android:layout_height="wrap_content"  
    android:max="200"
    android:progress="50"
    android:rotation="270"
    android:progressDrawable="@drawable/seek_bar"
  />  

seek_bar.xml :

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item
    android:id="@android:id/background"
    android:drawable="@drawable/seek_bar_background"/>
<item android:id="@android:id/progress"
    android:drawable="@drawable/seek_bar_progress" />
</layer-list>

Here seek_bar_background.png and seek_bar_progress.png are vertical images