How to get event when row loses focus

[carlhunterroach]

I'm adding validation to my XLForm instance.

I'd like this to happen at 3 places.

1. a call to formValidationErrors() to check for errors before I use all the values
2. when c() is called
   e.g., I note which field has the focus, and then when a Done button is tapped, I can tell the user that an email field is invalid
3. there is a hole in Row value assigned too late, otherwise nil #2. if the user taps another field then formRowDescriptorValueHasChanged() isn't called until the new field's content changes.

How can I check the content of a field when the user tries to tap to another field?

Or is this a wrong approach when using XLForm?

[gclsoft]

#351 How to get event XLFormRowDescriptorTypeSelectorPopover has changed select?
How did you solve it?