Hi,
That would be a very different design approach, you should indeed listen to inputs instead of keys, and so you would have a value ranging from -1 to 1 ( left or right, up or down).
use the action "getAxisVector" for this, it will return you a vector representing two inputs ( usually the joystick input), and then you use that to move the player around, this is different then listening to a key press and do a single action with it.
Experiment with this, if you are still stuck, I'll do another sample with this design instead.
Bye,
Jean