Implementing a countdown timer

To implement a countdown timer, we will create two objects: a field to display the current timer and a button to start the countdown. We will code two handlers: one for the button and one for the timer.

How to do it...

Perform the following steps to create a countdown timer:

1. Create a new main stack.
2. Place a field on the stack's card and name it timerDisplay.
3. Place a button on the stack's card and name it Count Down.
4. Add the following code to the Count Down button:

   on mouseUp
     local pTime
      
     put 19 into pTime
     put pTime into fld "timerDisplay"
     countDownTimer pTime
   end mouseUp

5. Add the following code to the Count Down button:

   on countDownTimer currentTimerValue
     subtract 1 from currentTimerValue
     put currentTimerValue into fld "timerDisplay"
     if currentTimerValue > 0 then 
       send "countDownTimer" && currentTimerValue to me 
         in 1 sec
     end if
   end countDownTimer

6. Test the code using a mobile simulator or...