Keira Knightlley and Adam Levine in “Begin Again.” (Andrew Schwartz/The Weinstein Company)

Wearing long sleeves in the boiling heat of New York City last summer, Maroon 5 lead singer Adam Levine started to think that maybe his full-body tattoos weren’t such a great idea.

Acting in his first-ever movie role in the music dramedy “Begin Again,” playing a musician who experiences ups and downs on the roller coaster of fame, Levine was asked by director John Carney to cover his ink with sleeves. In the 95-degree weather. This wasn’t something Levine thought about when he got the tattoos – which make perfect sense for a pop star, although not for a big-screen actor.

But who could have predicted he would ever have that problem? Certainly not Levine, whose rise through the celebrity stratosphere has taken more unexpected turns than most. From the early success of Maroon 5 to his pivot as a reality star on NBC’s “The Voice” to acting, Levine’s career has followed a curious path.

He claims he never plans ahead and just “rolls” with everything that has happened in the past several years – the shows, the movies, the endorsement and TV development deals. “I don’t think it’s smart to look too far into the future,” Levine said. “It’s a fine line between trying to manifest something to happen as far as your dreams are concerned, and then being too fixated on one thing happening one way.”

He’s speaking by phone from New York, doing the press rounds for “Begin Again,” which stars Mark Ruffalo as a down-on-his-luck record producer who meets a fledgling singer played by Keira Knightley. Levine plays Knightley’s music superstar boyfriend, who becomes her ex when he can’t resist the temptations of fame. Levine sounds a bit tired; it’s not yet noon and he claims he’s already done “17 zillion” interviews this morning.

Anyway, back to his unusual path:”I wanted to do music for my life and I wanted to be really successful, but I wasn’t aware that it could be this type of trajectory,” Levine said. “It’s always slightly different than you think it will be.”

True. Back when Levine and his high school friends started a band, he didn’t anticipate they would become the inescapable pop rockers Maroon 5. The group quickly found success in the early 2000s with monster debut album “Songs About Jane,” which featured smash singles “Harder to Breathe,” “This Love” and “Sunday Morning.” Even a decade later, “She Will Be Loved” is probably playing at this very moment over loudspeakers in various malls.

Adam Levine (in tattoos) in concert. (Bryan Bedder/Getty Images For American Express)

As often happens with a fast rise to fame, there have been a lot of detractors. As a lead vocalist with a unique falsetto and someone quite likely to bare his sculpted muscles for naked photo shoots, Levine attracted tabloid scrutiny from the beginning. With a confident swagger and tendency to spout quotes such as, “I love attention. I can’t stand not having it,” Levine (the first musician to become People’s Sexiest Man Alive) became a pop culture target. His parade of supermodel girlfriends – and engagement to Victoria’s Secret model Behati Prinsloo – didn’t really help matters.

“It’s strange that they’re so interested. I don’t think it’s that fascinating,” Levine said about the tabloid fascination with his personal life. “But hey, it’s flattering, I guess.”

Although Levine is self-deprecating, you do actually have to work hard to achieve the kind of multi-tiered success he’s enjoyed recently. While Maroon 5 stalled for several years in the mid-2000s, Levine catapulted back into the scene in January 2011 as a coach on “The Voice.” Millions tuned in and were drawn to Levine’s banter and his odd-couple friendship with fellow coach Blake Shelton.

Along with filming “The Voice” for two seasons a year, Levine found himself back in the spotlight with music, releasing the giant hit “Moves Like Jagger,” featuring his “Voice” co-star Christina Aguilera. Maroon 5 released a new album in the summer of 2012 called “Overexposed” – interpret the title how you wish. It went platinum.

Levine’s real-life ups and downs with fame were intriguing to “Begin Again” writer and director Carney, who was looking for an actor to play the role of Dave Kohl, the singer who can’t stay down-to-earth once he gets a big record contract.

“I never really thought about anyone else in the role,” Carney said. He first considered Levine when he saw his brief but hilarious cameo in a “30 Rock” scene opposite Alec Baldwin.

The two chatted via Skype, and then Levine recorded himself in the studio reading some lines. Carney (who directed the Oscar-winning musical drama “Once”) saw the footage and was sold.

While Levine had done some acting before with a small part in the second season of FX’s gorefest “American Horror Story” – in which his character memorably got his arm ripped off – this was an entirely different situation. And for him, it was pretty nerve-racking.

Adam Levine and his fiancee, Behati Prinsloo, attend a "Begin Again" screening. (Andrew H. Walker/Getty Images) Adam Levine and his fiancee, Behati Prinsloo, attend a “Begin Again” screening. (Andrew H. Walker/Getty Images)

Luckily, he got the hang of the big-screen experience fairly quickly. Levine, who in the film complements his long sleeves with a rock-star beard, shares most of his scenes with Knightley. While he was hesitant about going up against such an established actress, they were able to find an easy rapport through many hours filming scenes in a car together on the first day.

Carney was impressed by his performance. “I think he really delivered,” Carney said, citing his “star quality” along with his natural charisma and solid singing chops.

It helped that the Dave Kohl character wasn’t much of a stretch – in fact, there were a few scenes that hit a little too close to home for Levine. For example, Dave goes to a record label’s offices, where they tell him they love him and want him to be himself and not alter a thing – except for a few tiny fixes that wind up changing just about everything.

That, according to Levine, does not stray too far from the real-life recording industry. “That’s all they do in those boardrooms in those meetings. All they try to do is destroy the fabric of who you are because the record business is just silly,” he said. ” ‘Oh, you have to be this,’ or ‘You have to be that.’ But we never became successful by listening to them, so you take what they say with grain of salt.”