When I lock the doors , it drains the battery completely, what is happening?

Possible just coincidence. The life expectancy of a battery is 5yrs. Anything over that could mean a bad battery. If battery is ok.. You need to do a parasitic draw test to check for a drain on the battery and circuits. If you are not famaliar with a volt/amp meter and electrical I would suggest having a pro take a look

yes

You need to look at the door lock actuators, I'm guessing 1 is operating but staying on when locked and draining the battery. Try manually locking the doors and see what happens. It may come down to removing the door trims and disconnecting each lock in turn, don't forget the boot lock, until you find the culprit. Its possible you may hear the lock solenoid humming or buzzing or feels warm as its trying to lock the door unsuccessfully.

Disconnect the drivers door master switch for the door locks, if the locks stop cycling you need to replace the switch.

This seams to be a common problem with these. There was a problem on some Tucsons with a mis-aligned underhood switch that is connected to the alarm/security system. If it is misaligned, the security system is constantly drawing power but there are no outward signs that is doing so. Worth a look! :)
Also it could be the Radio . Those radios are known to drain batteries.
Also i have heard the door locks are a culprit.
I would check all three.
First i would pull the fuse for the radio and see what happens see if the battery gets drained still. if it doesn't get drained? Cool! Replace that radio with an after market one. If it does get drained ? I would pull the fuse for the door locks. and try that. The door locks on those vehicles are known to be speratric and can lock an unlock multiple times until the battery is dead. If thats the case with you? Bring it to a dealer and tell them what you did as far as testing.
Let me know what happens as far as outcome.
Please leave me a great feedback on here.

Completely remove the dome lite positive wire from the dome lite. If that doesn't fix it, then remove the door lock harness from the back of the door lock switch. Etc, etc. It will eventually indicate which is the problem by the process of elimination. I'd try that method. Eliminate each of the remaining items, until the drain stops. Garcuda

what is happening after you close the doors and lock it.. you may have a parasitic drain coming from a computer if everthing doesnt shut off or you just may have a bad battery or alternator. A bad diode in an alternator can drain a battery even when car is not in use

POWER DOOR LOCKS / STARTER SOLENOID CONTACTS SHORT /A BAD ALTERNATOR REGULATOR.AC AND HEATER BLOWER RELAY STUCK CLOSE.ALL THESE THING CAN CAUSE BATTERY DRAIN.

Pull fuse to locks and see if that solves the problem first, does the battery drain over night, could be a bad voltage regulator in alternator.

Recharge the battery. Or buy a new one. But make sure you have a fully charged battery.What happened was that the battery drained because it probably needs replacement. When the battery drained too low. The ECU deprogramed itself. When installing a new or fully charged battery. Start the car. You may have to remove the negative cable a few times then restart it for the CPU to go into the default settings.