In my android apps I was getting annoying problems that whilst playing sound the volume buttons would control the media volume, but when no sound was playing they would control the ringtone volume. I found the following by trial and error, hopefully this post will help people with the same problem.
This is done by placing a call of setVolumeControlStream in the onCreate part of your activity which takes on of the following values
Below shows the code required to set your applications default volume control to any of the above values:
Media Volume (Music/Video etc…)
I imagine this is also possible via and XML settings, if anyone knows of this I’d be very grateful to know how!