Because you used ViewGroup.LayoutParams
ViewGroup.LayoutParams layoutParams = new RelativeLayout.LayoutParams(containerWidth, fragmentHeight);
layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
but the method addRule is in the subclass RelativeLayout.LayoutParams
implemented, so you may want to use instead:
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(containerWidth, fragmentHeight);
layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);