We got the actor out Wednesday in L.A., where he was just leaving a gym session with his trainer -- strength and conditioning guru Jason Best -- and JM was actually willing to chat ... this, of course, while walking out shirtless and looking absolutely ripped.

BTW -- Best is the same guy who got him in peak condition for his bodybuilding role in "Magazine Dreams" -- and clearly, they're still working together ... 'cause JM looks great here.

Anyway, we chopped it up with Jon about a number of things going on in his life right now -- including this potential gig we've been hearing he has lined up for a film project ... although, the exact details are still a little murky. Jonathan did confirm to us, though, that he's getting in shape for "work" ... and when we asked if it was for the role, he certainly didn't deny it!

Our photog also talked to Jon about his relationship with Meagan Good -- which is going strong ... as the lovebirds continue to hit public events together ... and pack on PDA.

We asked Jon what makes MG different than other girlfriends he's had ... and he's got a pretty telling response, strongly hinting that Meagan's captured his heart and then some.

Jonathan called Meagan, who stood by him during his highly-publicized trial, his heart and credited their connection for their success as a couple.

Our chat with Jonathan here comes a day after it was revealed that his ex, Grace Jabbari -- who testified against him in December during a criminal trial -- sued him, claiming he assaulted her over the course of their relationship and defamed her as well.

Remember, Jonathan was convicted of misdemeanor assault and harassment in December ... and is currently awaiting sentencing. His legal team has filed to have the conviction tossed out -- and told us that they weren't surprised by Grace's recent filing.