You should set the screen as landscape,
you can do it by changing your code in "OnCreate" method and put this lines(if you don't need some of the lines just don't use them) :
// Set window fullscreen and remove
title bar, and force landscape
orientation
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
else if you don't want to change orientation, then you can follow this
question that i ask in order to change only the camera orientation.