my field
state = fields.Selection(string="Status", selection=[('draft', 'Draft'), ('confirm', 'Confirm'),
('validate', 'Validated'), ('refuse', 'Refuse'),('reset','Reset to Draft'),('cancel','Cancel'),
('approved', 'Approved'), ], default="draft", track_visibility='onchange', )
My view
button name="confirm_request" string="Confirm" class="oe_highlight" states="draft" type="object"/>
<button name="validate_request" string="Validate" class="oe_highlight" states="confirm" type="object" groups="hr.group_hr_user"/>
<button name="approve_request" string="Approve" class="oe_highlight" states="validate" type="object" groups="hr.group_hr_manager"/>
<button name="refuse_request" string="Refuse" states="confirm,validate" type="object" groups="hr.group_hr_user,hr.group_hr_manager"/>
<button name="%(launch_customer_wizard)d" type="action" state="validate"
string="Cancel" class="oe_highlight"/>
<field name="state" widget="statusbar" statusbar_visible="draft,confirm,validate"/>