How to calculate with TextEditingControllers in flutter?

Issue

So in flutter I have auto-calculated text fields and I want to calculate a result using a formula.

Let me first show what I am doing:

These are those text fields.

The code for these fields:

enum UnitType {
  meter,
  centimeter,
  feet,
  kilogram,
  gram,
}

class Units extends StatefulWidget {
  const Units({Key? key}) : super(key: key);

  @override
  State<Units> createState() => _UnitsState();
}

class _UnitsState extends State<Units> {
  final TextEditingController _feetController = TextEditingController();

  final TextEditingController _centimeterController = TextEditingController();

  final TextEditingController _meterController = TextEditingController();

  final TextEditingController _kilogramController = TextEditingController();

  final TextEditingController _gramController = TextEditingController();

  void _convertUnit(UnitType type) {
    double? ft = double.tryParse(_feetController.value.text) ?? 0;
    double? cm = double.tryParse(_centimeterController.value.text) ?? 0;
    double? m = double.tryParse(_meterController.value.text) ?? 0;
    double? kg = double.tryParse(_kilogramController.value.text) ?? 0;
    double? g = double.tryParse(_gramController.value.text) ?? 0;

    switch (type) {
      case UnitType.feet:
        _meterController.text = (ft / 3.281).toStringAsFixed(2);
        _centimeterController.text = (ft * 30.48).toStringAsFixed(2);
        break;
      case UnitType.meter:
        _centimeterController.text = (m * 100).toStringAsFixed(2);
        _feetController.text = (m * 3.281).toStringAsFixed(2);
        break;
      case UnitType.centimeter:
        _meterController.text = (cm / 100).toStringAsFixed(2);
        _feetController.text = (cm / 30.48).toStringAsFixed(2);
        break;
      case UnitType.kilogram:
        _gramController.text = (kg * 1000).toStringAsFixed(2);
        break;
      case UnitType.gram:
        _kilogramController.text = (g / 1000).toStringAsFixed(2);
        break;
    }
  }

The formula of BMI(body mass index) is Kg/m^2

Now I want when I click the BMI button I want the result to be displayed in the adjacent text field. The formula is BMI = Kilogram/(meter*meter).

I couldn't come up with any idea or code. Please help me out with some code to achieve my desired result.

Solution

1. You need to create one more TextEditingController, "bmiController" for example.
2. Then create a text field with a button, and assign bmi text controller to this field.
3. Create a method "calculate" and assign this method to the button.

Your calculate method should look like (I DIDN'T TEST THE CODE BELOW):

void calculate() {
  try {
    final kgValue = double.tryParse(_kilogramController.text);
    final meterValue = double.tryParse(_meterController.text);
    final bmiValue = kgValue / meterValue.pow(2);
    bmiController.text = bmiValue.toString();
  } catch (e) {
    // This is an example, you need to handle possible null exception anyway
    bmiController.text = 'Error';
  }
}

Answered By - lesha-native