SICalculator

import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    title: "Simple Interest Calculator",
    debugShowCheckedModeBanner: false,
    debugShowMaterialGrid: false,
    home: SIForm(),
    theme: ThemeData(
      brightness: Brightness.dark,
      primaryColor: Colors.deepPurple,
      accentColor: Colors.amber,
    ),
  ));
}

class SIForm extends StatefulWidget {
  @override
  _SIFormState createState() => _SIFormState();
}

class _SIFormState extends State<SIForm> {
  var _currencies = ["dollar", 'pound', 'rupees', 'euro'];
  var _currentItemSelected = 'rupees';

  TextEditingController principalControlled = TextEditingController();
  TextEditingController roiControlled = TextEditingController();
  TextEditingController termControlled = TextEditingController();
  String temp = 'SI calculated : 0 rupees';

  @override
  Widget build(BuildContext context) {
    TextStyle textStyle = Theme.of(context).textTheme.title;

    return Scaffold(
      resizeToAvoidBottomPadding: false,
      appBar: AppBar(
        title: Center(
          child: Text(
            "Simple Interest Calculator",
            style: TextStyle(
                fontFamily: 'Raleway',
                fontWeight: FontWeight.w700,
                color: Colors.white),
          ),
        ),
//        backgroundColor: Colors.blueAccent,
      ),
      body: Container(
        margin: EdgeInsets.all(10.0),
        child: Column(
          children: <Widget>[
            Center(child: getImage()),
            Padding(
                padding: EdgeInsets.only(top: 3.0, bottom: 3.0),
                child: TextField(
                  style: textStyle,
                  keyboardType: TextInputType.numberWithOptions(signed: false),
                  controller: principalControlled,
                  decoration: InputDecoration(
                    labelText: "Principal",
                    hintText: "Enter principal Ex- 12000",
                    labelStyle: textStyle,
                    border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(5.0)),
                  ),
                )),
            Padding(
                padding: EdgeInsets.only(top: 3.0, bottom: 3.0),
                child: TextField(
                  style: textStyle,
                  controller: roiControlled,
                  decoration: InputDecoration(
                    labelText: "Rate",
                    hintText: "In percent",
                    labelStyle: textStyle,
                    border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(5.0)),
                  ),
                )),
            Padding(
                padding: EdgeInsets.only(top: 3.0, bottom: 3.0),
                child: Row(
                  children: <Widget>[
                    Expanded(
                        child: TextField(
                      style: textStyle,
                      controller: termControlled,
                      decoration: InputDecoration(
                        labelText: "Term",
                        hintText: "Time in years",
                        labelStyle: textStyle,
                        border: OutlineInputBorder(
                            borderRadius: BorderRadius.circular(5.0)),
                      ),
                    )),
                    Container(
                      width: 25.0,
                    ),
                    Expanded(
                        child: DropdownButton<String>(
                      items: _currencies.map((String value) {
                        return DropdownMenuItem<String>(
                          value: value,
                          child: Text(value),
                        );
                      }).toList(),
                      value: _currentItemSelected,
                      onChanged: (String newValueSelected) {
                        _onDropDownItemSelected(newValueSelected);
                      },
                    )),
                  ],
                )),
            Padding(
              padding: EdgeInsets.only(bottom: 3.0, top: 3.0),
              child: Row(
                children: <Widget>[
                  Expanded(
                    child: RaisedButton(
                      color: Colors.deepPurple,
                      child: Text(
                        "Calculate",
                        textScaleFactor: 1.25,
                        style: TextStyle(
                            fontFamily: 'Raleway',
                            fontWeight: FontWeight.w700,
                            color: Colors.lightBlue),
                      ),
                      onPressed: () {
                        setState(() {
                          this.temp = _calculateTotalReturns();
                        });
                      },
                    ),
                  ),
                  Container(
                    width: 25.0,
                  ),
                  Expanded(
                    child: RaisedButton(
//                      color: Colors.deepPurple,
                        color: Theme.of(context).primaryColorDark,
                        textColor: Theme.of(context).primaryColorLight,
                        child: Text(
                          "Reset",
                          textScaleFactor: 1.5,
                          style: TextStyle(
                            fontFamily: 'Raleway',
                            fontWeight: FontWeight.w700,
                          ),
                        ),
                        onPressed: () {
                          setState(() {
                            _reset();
                          });
                        }),
                  )
                ],
              ),
            ),
            Padding(
              padding: EdgeInsets.all(5.0),
              child: Text(temp),
            )
          ],
        ),
      ),
    );
  }

  Widget getImage() {
    AssetImage assetimage = AssetImage("images/money.png");
    Image image = Image(
      image: assetimage,
      width: 100.0,
      height: 125.0,
    );
    return Container(
      child: image,
      margin: EdgeInsets.all(5.0),
    );
  }

  void _onDropDownItemSelected(String newValueSelected) {
    setState(() {
      this._currentItemSelected = newValueSelected;
    });
  }

  String _calculateTotalReturns() {
    double principal = double.parse(principalControlled.text);
    double roi = double.parse(roiControlled.text);
    double term = double.parse(termControlled.text);

    double total = principal + (principal * roi * term) / 100;
    String result = 'SI calculated : $total $_currentItemSelected';
    return result;
  }

  void _reset() {
    principalControlled.text = '';
    roiControlled.text = '';
    termControlled.text = '';
    temp = 'SI calculated : 0 rupees';
    _currentItemSelected = 'rupees';
  }
}