Expose onComplete #600
Description
Is your feature request related to a problem? Please describe.
I’m using ShowcaseView with a widget that contains a menu pager with two pages. I register a named scope and access it inside each page using ShowcaseView.getNamed. However, I currently have no way to know which index and which GlobalKey completed.
It would be helpful if the API exposed this information when a showcase step finishes.
Describe the solution you'd like
Expose the onComplete listener through ShowcaseView.getNamed, allowing widgets deeper in the tree to register a callback.