If not, did he do something that might be reasonably interpreted as apologizing?
From Obama’s origami cranes he left behind touches many hearts, the brother of Sadako Sasaki, who died of leukemia most likely caused by the atomic bombing of Hiroshima, interpreted Obama's hand-crafted origami cranes given to the Hiroshima Peace Museum as an apology.
Sasaki’s 74-year-old brother, Masahiro, said on May 28
he was deeply moved by the president taking an interest in his
sister’s origami cranes.
“I took his gesture as his apology, strong determination to restore
peace and warm, generous heart,” he said.
Hiroshima survivors: Obama speech moving, 'more than enough' surveys ordinary Hiroshima residents who lived through or were born soon after the atomic bombing. One of them said that it was an apology, while another implicitly said it was not an apology by saying that a US apology can't happen until Japan apologises for Pearl Harbor:
EIJI HATTORI, 73, SURVIVOR
"I think (Obama's speech) was an apology."
Hattori's parents and grandparents, who sold rice near where the bomb fell, all either died that day or in the years that followed. Hattori, who now has three types of cancer, earlier said that an Obama apology would ease his suffering.
"I feel different now. I didn't think he'd go that far and say so much. I feel I've been saved somewhat. For me, it was more than enough."
and
KENJI ISHIDA, 68, TAXI DRIVER
"A sitting U.S. president visiting Hiroshima is just the first step.
We're still 10 years from the possibility of a president issuing an
apology."
Born two years after the bomb was dropped, Ishida remembers growing up
with bomb survivors whose skin was scarred.
"Japan has to apologize for Pearl Harbor, too, if we're going to say
the U.S. must apologize ... That's not possible, given the countries'
current situations. In America, people say the war ended early because
they dropped the atomic bomb. If a president apologized for this, it
would raise hell in the U.S.
"We can't tell North Korea not to have nukes when the U.S. has them,
but the U.S. developed them first ... It's not possible to get rid of
nuclear weapons when they're being used as deterrence."
The blog post Obama’s visit to Hiroshima is viewed as “a sort of” apology by the people of Japan. surveyed Japanese people, and concluded that it a large proportion regard the visit as some sort of apology:
To study this, we performed a series of surveys on a nation-wide Japanese sample of about 1,000 people, and on a similar number of people currently living in Hiroshima. We asked if they support the visit itself, if they see sincerity in the visit, and if they see the visit as a sort of apology (even though the White House denies it).
...
On the question which asks whether they consider the visit to be “a sort of apology,” their answer is “Yes”. We believe this is the most important finding of the survey: that the visit is considered as a “non-apology apology” in both Hiroshima and national samples even though the White House states that President Obama will not revisit the decision to use the atomic bomb and there is no intention to make an apology. For the national sample, 77.3 per cent see Obama’s visit as a sort of apology, and for Hiroshima, the number is 85.6 percent. As Figure 1 shows, the national and Hiroshima samples are statistically different – more people in Hiroshima see it as an implicit apology than the national average.