Main layout with data binding. It includes a secondary layout and pass to it a variable.

data_binding_include_main_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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"
    xmlns:bind="http://schemas.android.com/apk/res-auto">

    <data>
        <variable 
            name="mainUser"
            type="it.communikein.myunimib.User" />
    </data>

    <android.support.design.widget.CoordinatorLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar"
            android:layout_width="match_parent"
            android:layout_height="@dimen/app_bar_height"
            android:fitsSystemWindows="true"
            android:theme="@style/Theme.MyUnimib.AppBarOverlay">

            <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/toolbar_layout"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                app:contentScrim="?attr/colorPrimary"
                app:layout_scrollFlags="scroll|exitUntilCollapsed"
                app:toolbarId="@+id/toolbar">

                <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    android:layout_width="match_parent"
                    android:layout_height="?attr/actionBarSize"
                    app:layout_collapseMode="pin"
                    app:popupTheme="@style/Theme.MyUnimib.PopupOverlay" />

            </android.support.design.widget.CollapsingToolbarLayout>
            
        </android.support.design.widget.AppBarLayout>

        <include android:id="@+id/secondary"
            layout="@layout/data_binding_included_secondary_layout"
            bind:secondaryUser="@{mainUser}"/>

    </android.support.design.widget.CoordinatorLayout>
</layout>