Possible to get reference to a View without setting the ContentView of an Activity

Question

I want to be able to get reference to a RelativeLayout in the same way as

RelativeLayout relative = (RelativeLayout)findViewById(R.id.relative);

but without setting the ContentView of the Activity. I think it may have something to do with Infalter? My ultimate aim is to get this and add it as a child view of a custom view object.