Image is copyright of Disney and Lucasfilm Ltd.
If you have seen the Star Wars: The Force Awakens, you probably left the movie theater with some questions in your head about R2-D2's role in the movie. Well J. J. Abrams has explained it.
This article contains spoilers for Episode VII, continue reading at your own risk.
Entertainment Weekly reported that Abrams explained R2's sudden "awakening" in a post screening Q&A. This is a summary of what he said:
R2-D2 falls into a coma-like state after Kylo Ren slaughtered the other Jedi apprentices. It is the equivalent of a droid depression. He remains in this state until BB-8 talks to him. What he says to him is something like "I have a piece of a map, do you have the rest?" Although R2-D2 is in low power mode, he still hears BB-8's words and starts looking for the map. When he finds it, he decides to wake up to inform the others.
Now how does R2-D2 have the rest of the map? Well, that's quite simple. The map is not really a map to Luke Skywalker. It is a map of all the Jedi temples that the Empire had (as indicated by Kylo Ren). The map is missing a part. It is not that Luke did that on purpose, it is just the way it is. R2-D2 acquired the map while he was connected to the Imperial network while on the Death Star 38 years ago (Episode IV: A New Hope). So the map to the first Jedi temple is the map that leads to Luke.
It does make sense, but in my opinion, if you have to give such a long explanation, then the movie didn't do a good job of making it clear enough to the audience.