He committed on the spot.
"It's been my dream forever," Johnson said of becoming a Wildcat. "I grew up rooting for the Wildcats."
Johnson did not make a huge deal out of signing day but did have a small ceremony at his school with his teammates, coaches and family.
Not only is Johnson getting to play for the team he grew up rooting for but he gets to play for a program that has done a great job developing wing players.
"At Arizona I will have a chance to complete my game," Johnson said.
The most intriguing thing about Johnson is he continued to get better. The summer before his junior year he looked like a mid-major prospect with a big time jump shot. By the time August rolled around he was quicker, faster and more athletic. Most importantly, the shot was just as good, if not better.
"I am able to create off the dribble," Johnson said of his improvements. "I've worked on my speed. I'm a lot quicker. I'm a lot more explosive now.
Before he will play at Arizona Johnson has one last season left at Phoenix's Thunderbird High School. The team is ranked 24th in the nation by USA Today and for Johnson nothing short of a state title will suffice.
Johnson has played with all of his fellow signees either in camps or on the AAU circuit. He's got a good relationship with all of them.
"It is going to be fun," Johnson said. "We've got a great relationship."
Johnson is especially close with fellow Arizonan Jerryd Bayless, a former AAU teammate and soon to be future teammate.
"I am glad we are going to be playing together," Johnson said. "We think we can push each other and help one another get to the next level."