Fails on calculate

[LeeHunter]

Whether I run this code my version or the "completed" version I get the following message after pressing the Calculate button:

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building Builder(dirty):
The method '>=' was called on null.
Receiver: null
Tried calling: >=(25.0)

The relevant error-causing widget was:
MaterialApp file:///Users/leehunter/angelayucourse/BMI-Calculator-Flutter-Completed/lib/main.dart:9:12
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1 CalculatorBrain.getResult (package:bmi_calculator/calculator_brain.dart:17:14)
#2 _InputPageState.build.. (package:bmi_calculator/screens/input_page.dart:224:38)
#3 MaterialPageRoute.buildPage (package:flutter/src/material/page.dart:87:27)
#4 _ModalScopeState.build. (package:flutter/src/widgets/routes.dart:710:43)
...
════════════════════════════════════════════════════════════════════════════════════════════════════

[hoctor]

You may be declaring _bmi twice, check inside calculateBMI, must be like this

class CalculatorBrain {
CalculatorBrain({this.height, this.weight});

final int height;
final int weight;

double _bmi;

String calculateBMI() {
_bmi = weight / pow(height / 100, 2);
return _bmi.toStringAsFixed(1);
}

[LeeHunter]

Thanks but that's not it.

[elliotxin]

@LeeHunter you should initialize the "_bmi" value first sine the flutter update to the new version. must like this: "double _bmi = 0.0;"

[mesutdinler]

@LeeHunter you should initialize the "_bmi" value first sine the flutter update to the new version. must like this: "double _bmi = 0.0;"

thanks a lot.

[fcrignon]

hello, I fixed it doing like follow:

I change the a bit this two methods in calculator_brain.dart

String getResult(String bmi) {
_bmi = double.parse(bmi);
...

}

String getInterpretation(String bmi) {
_bmi = double.parse(bmi);
...

}

and I added one line in the onTap property in input_page.dart

onTap: () {
CalculatorBrain calc =CalculatorBrain(height: height, weight: weight);
String bmi =calc.calculateBMI();
Navigator.push(...)
);
},

[mehrheer]

GetResult() method is being called before the calculateBMI() method, so even if you initialize _bmi to be 0.0, your app won't crash anymore but you would still get the wrong output on your screen.

[Mahad61]

i have the same error then after i check if i change the sequence name like first bmiResult then resultText and then interpretation according to the result_page constructor in input_page navigator my error fixed try it
BottomButton(
label: 'CALCULATE',
onTap: () {
CalculatorBrain calc =
CalculatorBrain(weight: weight, height: height);
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ResultsPage(
bmiResult: calc.calculateBMI(),
resultText: calc.getResult(),
interpretation: calc.getInterpretation(),
)));
},
)

[Hoxtygen]

hello, I fixed it doing like follow:

I change the a bit this two methods in calculator_brain.dart

String getResult(String bmi) {
_bmi = double.parse(bmi);
...

}

String getInterpretation(String bmi) {
_bmi = double.parse(bmi);
...

}

and I added one line in the onTap property in input_page.dart

onTap: () {
CalculatorBrain calc =CalculatorBrain(height: height, weight: weight);
String bmi =calc.calculateBMI();
Navigator.push(...)
);
},

This is what worked for me. Good job man.

[felexkuria]

thanks @Hoxtygen worked like charm

[fobf]

class CalcuatorBrain {
  CalcuatorBrain({this.height, this.weight});

  final int? height;
  final int? weight;

  final double _bmi = 0.0;

  String calculateBMI() {
    double _bmi = weight! / pow(height! / 100, 2);
    // bmi != null ? bmi : null; // null check
    return _bmi.toStringAsFixed(1);
  }

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

  String getInterpretation() {
    if (_bmi >= 25) {
      return 'Try to exercise more.';
    } else if (_bmi >= 18.5) {
      return 'Good job,';
    } else {
      return 'You can eat a bit more.';
    }
  }
}

can somb tell me why I am always getting the underweight results? BMI is different but results are the same.

[fobf]

I found the answer :

import 'dart:math';

class CalcuatorBrain {
  CalcuatorBrain({this.height, this.weight})
      : _bmi = weight! / pow(height! / 100, 2);

  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';
    }
  }

  String getInterpretation() {
    if (_bmi >= 25) {
      return 'Try to exercise more.';
    } else if (_bmi >= 18.5) {
      return 'Good job,';
    } else {
      return 'You can eat a bit more.';
    }
  }
}

from here:
https://stackoverflow.com/questions/69245524/dart-flutter-bmi-code-returns-bmi-value-but-other-values-are-wrrong/69246272#69246272

[TechParkBB]

this works for me in the latest Android Studio version

`class CalculatorBrain {
CalculatorBrain({required this.height, required this.weight});
final int height;
final int weight;
double _bmi = 0.0;

String calculateBMI() {
_bmi = weight / pow(height / 100, 2);
return _bmi.toStringAsFixed(1);
}`