The specified child already has a parent. You must call removeView() on the child's parent first (Android)

The error message says what You should do.

// TEXTVIEW
if(tv.getParent() != null) {
    ((ViewGroup)tv.getParent()).removeView(tv); // <- fix
}
layout.addView(tv); //  <==========  ERROR IN THIS LINE DURING 2ND RUN
// EDITTEXT

simply pass the argument

attachtoroot = false

View view = inflater.inflate(R.layout.child_layout_to_merge, parent_layout, false);

I came here on searching the error with my recyclerview but the solution didn't work (obviously). I have written the cause and the solution for it in case of recyclerview. Hope it helps someone.

The error is caused if in the onCreateViewHolder() the following method is followed:

layoutInflater = LayoutInflater.from(context);
return new VH(layoutInflater.inflate(R.layout.single_row, parent));

Instead it should be

return new VH(layoutInflater.inflate(R.layout.single_row, null));