Flutter set Value to zero when it WOULD fall below zero-CodePudding

I am trying to create a drink tracker where I can track my hydration during the day

Therefore I created this app. The problem is: When I press "add" 500ml, then press "remove" 750ml it goes to minus 250ml. I can only manage to set the counter to zero when I press any decrement button again after it is already a negativ value! Here is the code:

      Future<void> _decrementCounter({required int amount}) async {
    final prefs = await SharedPreferences.getInstance();

    setState(() {
      if(_counter<=0||_counter==-250){
        _counter = prefs.getInt('counter') ?? 0;
        _counter = 0;
        prefs.setInt('counter', _counter);
      }else{
      _counter = (prefs.getInt('counter') ?? 0) - amount;
      prefs.setInt('counter', _counter);
      }
    });
  }

I hope you understand my usecase and can help me with this issue!

CodePudding user response：

I would just check if the current counter minus the passed value is less than 0. If it is, then I would put 0 in counter and otherwise the calculation. And then you save that in your SharedPreferences again.

setState(() {
    _counter = (_counter - amount) < 0 ? 0 : (_counter - amount);
    prefs.setInt('counter', _counter);
  }
}