Dart/flutter How To Change The Timer Inside Periodic After Every Time

I'm making a custom logic for showing ads in my app, so when the user opens the app after 1 min pops up an ad then supposed this 1 min to get increased by 1 min every time, So x be

Solution 1:

I think you cannot do it. You can alternatively cancel the current timer and start a new timer based on conditions. Check the following pseudo-code

  Timer.periodic(Duration(minutes: 5), (timer) {
      if(condition){
        timer.cancel();
        createNewPeriodicTask();
      }
      // task code
  });