NoSuchMethodError,widgets库捕获的异常

Question

class calculator {
  calculator({this.height, this.weight});
  final int height;
  final int weight;
  double _bmi;
  String calculatebmi() {
    _bmi = (weight / pow(height / 100, 2));
    return _bmi.toStringAsFixed(1);
  }

  String getresult() {
    if (_bmi >= 25) {
      return 'Overweight';
    } else if (_bmi > 18.5) {
      return 'Normal';
    } else {
      return 'Underweight';
    }
    return ' ';
  }

  String getRemarks() {
    if (_bmi >= 25) {
      return 'Your weight is more than average body weight, try to excercise.';
    } else if (_bmi > 18.5) {
      return 'Your weight is normal';
    } else {
      return 'Your weight is less than average body weight, try to eat more';
    }
  }
}

`GestureDetector(  
onTap: () {
calculator cal = calculator(height: height, weight: weight);
Navigator.push(context, MaterialPageRoute(builder: (context) => results(result: calculator().getresult(), bmi: calculator().calculatebmi(), remarks: calculator().getRemarks())));
},)`

Answer 1

发生问题是因为value_bmi为NULL。这是因为您没有调用calculatebmi（）。

您正在使用calculator（）的空参数计算BMI。所以，与其设置

bmi:calculator().getresult();

用作：

bmi : cal.getresult();         // You already have insteance of calculator (cal)