Full details are here “somewhere” here on the forum (i’ve lost track), but in short:
“pretend” that you’re going to do an email share, and set up the options accordingly (my use was just to share a captured image, so didn’t care that i couldn’t prefill text for subject or body),
now, and this is the key, and is the kludgy/hokey part that prevents it from being usable in real-world applications, but does prove the concept/theory: go into your settings-apps, find whatever app you currently have associated with the email share intent (it’s probably gmail :D), and clear out that association.
now when you attempt to share an email you’ll get the “just once/always” chooser.
so fire up your app, try to share an email, then choose facebook, just once.
and done (assuming you have the facebook app installed, of course), your pic was just posted.
now try it again, but choose twitter (assuming you have twitter app installed) just once. and done, photo posted.
now try it again, but choose g+ just once, and done, photo posted.
now try it again, but choose ANY OTHER app you happen to have that has some reasonable chance of knowing what to do with an image file, and it probably “just works” too.
when done experimenting, select your original email client and “always” to put things back the way they were.
the point is: if Corona allowed you to FORCE the creation of a chooser (so as to override any pre-existing association, and is literally a one-line addition if you’ve already got all the other code in place) you could issue a “generic” share intent and do “simple sharing” on android+facebook today.