android.support.v7.widget.RecyclerView作为根视图

Question

Can the android.support.v7.widget.RecyclerView be the root view in a layout file or I must add it as a child of "RelativeLayout" element?

Layout A

  <android.support.v7.widget.RecyclerView
      android:id="@+id/itemsRecyclerView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      app:layoutManager="android.support.v7.widget.GridLayoutManager"
      app:spanCount="2"/>

---

Layout B

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:app="http://schemas.android.com/apk/res-auto"
                xmlns:tools="http://schemas.android.com/tools"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                tools:context=".ui.activity.MainActivity">

  <android.support.v7.widget.RecyclerView
      android:id="@+id/itemsRecyclerView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      app:layoutManager="android.support.v7.widget.GridLayoutManager"
      app:spanCount="2"/>

</RelativeLayout>

Answer 1

As official doc says:

The root element can be either a ViewGroup, a View, or a element, but there must be only one root element and it must contain the xmlns:android attribute with the android namespace as shown.

so you could use RecyclerView as the root view:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        >


</android.support.v7.widget.RecyclerView>

Answer 2

Yes you can take recyclview as root element of activity.But it's a good practice to take any view group as a root and recyclview as child view.

Here is code:

<android.support.v7.widget.RecyclerView 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/transparent"
android:orientation="vertical"
app:layoutManager="android.support.v7.widget.LinearLayoutManager" />