Cambridge writer Lois Lowry is keeping an eye on the adaptation of her classic young adult novel, “The Giver.’’ The author tweeted several shots from her recent trip to South Africa, where she watched production and met with the movie’s stars Jeff Bridges, Katie Holmes, Alexander Skarsgard, and Brenton Thwaites. Bridges, who plays the Giver character — a man who keeps memories for a utopian society that attempts to live without pain — is one of the producers on the film and has been planning it for years. Looks like Lowry had a ball on the set. Among the photos she tweeted was one with Holmes shot by the actress’s 7-year-old daughter, Suri Cruise. “Going to ‘Ender’s Game’ with my grandsons tomorrow,’’ Lowry tweeted upn her return, referring to the sci-fi action film based on the novel Orson Scott Card. “Will look at it with an insider’s eye now, I think.’’ “The Giver’’ is expected to be released next summer.