How to inflate one view with a layout

You inflate an XML resource. See the LayoutInflater doc .

If your layout is in a mylayout.xml, you would do something like:

View view; 
LayoutInflater inflater = (LayoutInflater)   getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
view = inflater.inflate(R.layout.mylayout, null);

RelativeLayout item = (RelativeLayout) view.findViewById(R.id.item);

I'm not sure I have followed your question- are you trying to attach a child view to the RelativeLayout? If so you want to do something along the lines of:

RelativeLayout item = (RelativeLayout)findViewById(R.id.item);
View child = getLayoutInflater().inflate(R.layout.child, null);
item.addView(child);