title: How to make android:drawable/btn_default transparent
body: <p>I am using btn_default for my background of a spinner and that works nicely.  I would now like to make the btn_default transparent.  I have read about maybe using nine patch to make my own button based on btn_default but I can't find btn_default.png anywhere.  I am not sure if this is how to do it so if someone explain how to make the btn_default transparent it would be much appreciated.</p>