<LinearLayout
    android:id="@+id/layout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

<LinearLayout
    android:id="@+id/layout2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true">

    <ImageButton
        android:layout_width="match_parent"
        android:layout_height="50dp" />
</LinearLayout>