product_barcode_generator/product_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        
        <record id="view_product_category_simple_ean_form" model="ir.ui.view">
            <field name="name">product.category.form</field>
            <field name="model">product.category</field>
            <field name="inherit_id" ref="product.product_category_form_view"/>
            <field name="arch" type="xml">
                <field name="type" position="after">
                    <field name="ean_sequence_id" domain="[('barcode_sequence', '=', 1)]"
                        context="{'default_name': name and 'EAN ' + name or 'EAN', 'default_barcode_sequence': 1}"/>
                    <newline/>
                </field>
            </field>
        </record>
        
        <record id="view_product_simple_ean_form" model="ir.ui.view">
            <field name="name">product.product.form</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="product.product_normal_form_view"/>
            <field name="arch" type="xml">
                <field name="ean13" position="after">
                    <field name="ean_sequence_id" domain="[('barcode_sequence', '=', 1)]"
                        context="{'default_name': name and 'EAN ' + name or 'EAN', 'default_barcode_sequence': 1}"
                        class="oe_edit_only"/>
                    <button
                        string="Generar"
                        name="generate_ean13"
                        attrs="{'invisible': [('ean13', '!=', False)]}"
                        type="object" colspan="2"/>
                </field>
            </field>
        </record>
        
    </data>
</openerp>