How to change layout size (and other parameters) in code

It is really easy to change layout parameters, but you have to pay attention here: I'm changing LinearLayout, but parent of this layout - RelativeLayout. So I have to set LayoutParams for RelativeLayout otherwise I'll get ClassCastException.

LinearLayout layout = (LinearLayout)findViewById(R.id.activity_layout);
layout.setLayoutParams(new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));