activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#00BBFF"
    android:id="@+id/my_layout">

    <fragment
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:name="com.example.abhishek.fragments.FragmentA"
        android:id="@+id/fragment"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <fragment
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:name="com.example.abhishek.fragments.FragmentB"
        android:id="@+id/fragment2"
        android:layout_below="@+id/fragment"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>