Hi @hwanghc123 ,
the first thing that I see is that you send capital letters (i.e. "A" , "S",...)
while you are expecting lowercase letters (i.e. "a", "s", ...). The receiver (Arduino code) will never match the case.
Second (multiple doubts) the HC06 baudrate is surely 9600 ? to which pins is attached ? Which Arduino board are you using ? The AI2 code that you posted does not show the initialization of the BT (on phone side).....
As you can see, there are many things that have to be verified before you expect it's working.
My suggestion is to have a look 
on the tutorials that @Juan_Antonio or @Nilton_Santos have prepared and are available on the community: just type "Arduino tutorials" or "bluetooth HC06" in the search cell. I believe you will find the solution therein.
The link below is just an example of what you can find on your own.
(Bluetooth HC-06. Arduino. Send. Receive. Send text file. Multitouch. Image)
Best wishes. 