Not a walk. Walking, holding the ball and moving beyond the allowable range are walking. According to the rules, to catch the ball in the air, both feet should touch the ground one after another, and the foot that touches the ground first is the center foot. Both feet should land at the same time, and both feet can be the center foot (the foot that moves later is the center foot). Raising the center foot can pass the ball and shoot, but it can't dribble. When passing or shooting with the center foot raised, the center foot cannot touch the ground before the ball leaves the hand. At the beginning of dribbling, the ball must leave the hand first, and then the center foot can be lifted. Violation of the above provisions is a step.

According to what you said, even if both feet land successively, you can't move the foot that landed first, because that is the center of gravity. If you jump directly to the basket and make a layup, you must jump with that foot or both feet at the same time.