title: SAP UI5 value help only for Smartfield
body: <p>I have a <em>smartfield</em> that has a <code>value-list</code> annotation. 
  I would like it to behave such that text input is disabled for the field so the user is forced to open the value help when he clicks on the field, and select from a valid list - much like the <code>valueHelpOnly</code> property of <code>sap.m.Input</code>. I was looking for a similar property for <code>smartfield</code> but there isn't seem to be one?</p>
  
  <p>If there's no standard property for this, what's the best way to validate input vs valid value help values for <code>smartfields</code>?
  Thanks in advance.</p>
  
  <p><a href="https://i.stack.imgur.com/nuLGH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nuLGH.png" alt="enter image description here"></a></p>