How to set a background image in navigator view

image_navigatorview.md

Just add: android:background="@drawable/image" (in this case fondo_menu):

<android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        android:background="@drawable/fondo_menu"
        app:itemTextColor="#ffffff"
        app:headerLayout="@layout/nav_header_principal"
        app:menu="@menu/activity_principal_drawer"
        android:theme="@style/AppTheme"
        android:layout_marginLeft="50dp"/>

Take in account that Android Studio, oddly, doesn't suggest for this line the drawable directory, neither its content, so you can think mistakenly this is not the way.