use attribute force_save="1" in view to save value of readonly field.
<field name="payment_type" readonly="1" force_save="1"/>
it will save value of payment_type field when onchange trigger.
use attribute force_save="1" in view to save value of readonly field.
<field name="payment_type" readonly="1" force_save="1"/>
it will save value of payment_type field when onchange trigger.