social/mail_activity_done/views/mail_activity_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <!--
        Copyright 2018 Eficent <https://www.eficent.com>
        License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl.html).
    -->
    <record id="mail_activity_view_form_popup" model="ir.ui.view">
        <field name="name">mail.activity.view.form.popup</field>
        <field name="model">mail.activity</field>
        <field name="inherit_id" ref="mail.mail_activity_view_form_popup"/>
        <field name="priority">20</field>
        <field name="arch" type="xml">
            <field name="activity_type_id" position="after">
                <field name="state"/>
                <field name="date_done"/>
            </field>
            <button name="action_done" position="attributes">
                <attribute name="attrs">{'invisible':[('state', '=', 'done')]}</attribute>
            </button>
        </field>
    </record>

    <record id="mail_activity_view_search" model="ir.ui.view">
        <field name="name">mail.activity.view.search</field>
        <field name="model">mail.activity</field>
        <field name="inherit_id" ref="mail.mail_activity_view_search"/>
        <field name="arch" type="xml">
            <field name="res_model_id" position="after">
                <field name="done"/>
                <field name="active"/>
                <filter string="Completed Activities" name="activities_completed"
                        domain="[('active', '=', False), ('state', '=', 'done')]"/>
            </field>
            <filter name="activities_overdue" position="attributes">
                <attribute name="domain">[('date_deadline', '&lt;', context_today().strftime('%Y-%m-%d'))]</attribute>
            </filter>
            <filter name="activities_today" position="attributes">
                <attribute name="domain">[('date_deadline', '=', context_today().strftime('%Y-%m-%d'))]</attribute>
            </filter>
            <filter name="activities_upcoming_all" position="attributes">
                <attribute name="domain">[('date_deadline', '&gt;', context_today().strftime('%Y-%m-%d'))]</attribute>
            </filter>
        </field>
    </record>

    <record id="mail_activity_view_tree" model="ir.ui.view">
        <field name="name">mail.activity.view.tree</field>
        <field name="model">mail.activity</field>
        <field name="inherit_id" ref="mail.mail_activity_view_tree"/>
        <field name="arch" type="xml">
            <field name="date_deadline" position="after">
                <field name="state"/>
                <field name="date_done"/>
            </field>
            <tree position="attributes">
                <attribute name="decoration-muted">state == 'done'</attribute>
                <attribute name="decoration-danger">date_deadline &lt; current_date and state != 'done'</attribute>
                <attribute name="decoration-success">date_deadline == current_date and state != 'done'</attribute>
            </tree>
        </field>
    </record>

    <record id="mail_activity_view_calendar" model="ir.ui.view">
        <field name="name">mail.activity.view.calendar</field>
        <field name="model">mail.activity</field>
        <field name="inherit_id" ref="mail.mail_activity_view_calendar"/>
        <field name="priority" eval="2"/>
        <field name="arch" type="xml">
            <field name="summary" position="after">
                <field name="state"/>
                <field name="date_done"/>
            </field>
        </field>
    </record>

</odoo>