1. order model

              class orders(models.Model):
                      _name='pickabite.orders'
                      _rec_name='order_id'

                  state = fields.Selection([
                              ('draft','Draft'),
                              ('confirmed', 'Confirmed'),
                              ('bill','Bill'),
                              ('in_payment', 'In Payment'),
                              ('paid', 'Paid'),
                              ('cancel', 'Cancelled'),],
                              string='Status', index=True, readonly=True, default='draft',
                              track_visibility='onchange', copy=False)


                              #register payment button action
                              @api.multi
                              def in_payment(self):
                                  self.write({'state': 'in_payment'})
                                  return {
                                      #'name': self.order_id,
                                      'res_model': 'pickabite.payment',
                                      'type': 'ir.actions.act_window',
                                      'context': {},
                                      'view_mode': 'form',
                                      'view_type': 'form',
                                      'view_id': self.env.ref("pickabite.payment_form_view").id,
                                      'target': 'new'
                                  }

                  

2. -payment model

                  class payment(models.Model):
                        _name='pickabite.payment'
                        _rec_name='bill_id'
                        bill_id=fields.Many2one('pickabite.orders',string='Bill Id')
                        customer_id=fields.Many2one(related='bill_id.customer_name',
                                string='Customer Id')
                        bill_amount=fields.Float(related='bill_id.order_price',
                                string='Bill amount')

                                

3. Order Form View

               <record model="ir.ui.view" id="pickabite.order_form">
        <field name="name">Orders</field>
        <field name="model">pickabite.orders</field>
        <field name="arch" type="xml">
        <form string="Orders">
            <header>
                 
                <button style=" background-color: lightblue;"
                    name="in_payment" string="Register Payment" states="bill"
                    type="action"/>
                 
                <field name="state" widget="statusbar"
                    statusbar_visible="draft,confirmed,bill,in_payment,paid,
                                            cancel" />
            </header>
            <form>
                  <!--       -->
        </form>
      </field> 
    </record>
    
                                

4. Payment Form View

                                <record model="ir.ui.view" id="pickabite.payment_form_view">
        <field name="name">Payment Form View</field>
        <field name="model">pickabite.payment</field>
        <field name="arch" type="xml">
        <form>
                 <!--  -->
        </form>
      </field> 
    </record>

                                

5. window action

                                <record model="ir.actions.act_window" id="order_menu_action">
        <field name="name">Orders</field>
        <field name="res_model">pickabite.orders</field>
        <field name="view_type">form</field>
          <field name="view_mode">kanban,tree,form</field>
        <field name="domain">[]</field>
        <field name="help" type="html">
          <p class="o_view_nocontent_smiling_face">Create The First
                   Order</p>
        </field>
    </record>

                                

6. payment menu

                                <record model="ir.actions.act_window" id="payment_menu_action">
        <field name="name">Payment</field>
        <field name="res_model">pickabite.payment</field>
        <field name="view_type">form</field>
          <field name="view_mode">form</field>
          <!--field name="view_id"/>
          <ref="pickabite.payment_form_view"/-->
          <field name="target">current</field>
    </record>