Hi,
Please refer to the code below:
Python
from odoo import fields, models, _
class ProjectTask(models.Model):
_inherit = "project.task"
def action_view_invoice(self):
invoice = self.sale_order_id.invoice_ids
return {
'name': _('Invoice'),
'view_mode': 'list,form',
'res_model': 'account.move',
'type': 'ir.actions.act_window',
'domain': [('id', 'in', invoice.ids)],
}
XML
<record id="view_task_form2" model="ir.ui.view">
<field name="name">project.task.view.form</field>
<field name="model">project.task</field>
<field name="inherit_id" ref="project.view_task_form2"/>
<field name="arch" type="xml">
<xpath expr="//div[@name='button_box']" position="inside">
<button
string="Invoice"
class="oe_stat_button"
name="action_view_invoice"
type="object"
icon="fa-dollar"/>
</xpath>
</field>
</record>
Hope it helps.