Building a Currency Converter in Flutter

In this article, we will be building a currency converter application in Flutter. You can find a youtube video at the end of the article with my step-by-step process.

Let’s dive straight into the code.

main.dart

import 'package:flutter/material.dart';
import 'package:testapp/dollar_to_inr.dart';
import 'package:testapp/inr_to_dollar.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: CurrencyConverter(),
    );
  }
}

class CurrencyConverter extends StatelessWidget {
  const CurrencyConverter({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Currency Converter'),
      ),
      body: Center(
        child: Column(
          //for the buttons to be in center
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              onPressed: () {
                //on pressing dollar to INr we should navigate
                //to the dollar_to_inr widget
                Navigator.of(context).push(
                    MaterialPageRoute(builder: (context) => DollarToINR()));
              },
              child: Text('Dollar To INR'),
            ),
            //create sized box for space between
            //two buttons
            const SizedBox(
              height: 30,
            ),
            //another elevated button for inr to dollar
            ElevatedButton(
              onPressed: () {
                //on pressing this button
                //we should naviaget to inr_to_dollar.dart
                //widget
                Navigator.of(context).push(
                    MaterialPageRoute(builder: (context) => InrToDollar()));
              },
              child: Text(
                'INR to Dollar',
              ),
            )
          ],
        ),
      ),
    );
  }
}

inr_to_dollar.dart

import 'package:flutter/material.dart';
import 'package:flutter/src/widgets/framework.dart';
import 'package:flutter/src/widgets/placeholder.dart';

class InrToDollar extends StatefulWidget {
  const InrToDollar({super.key});

  @override
  State<InrToDollar> createState() => _InrToDollarState();
}

class _InrToDollarState extends State<InrToDollar> {
  //create controller for inr
  TextEditingController inrController = TextEditingController();
  //creating the varibale to store the dollar value
  double dollar = 0.0;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Inr to Dollar Converter'),
      ),
      body: Container(
        //give some padding
        padding: EdgeInsets.all(20),
        //here we need to create
        //one text filed to take input form user
        //and one button
        //so we will use here column widget
        child: Column(
          children: [
            TextField(
              controller: inrController,
              //some box around text field
              decoration: const InputDecoration(
                border: OutlineInputBorder(),
                //labele text
                labelText: 'Enter Inr',
              ),
            ),
            //need some space between
            //textfield and button
            const SizedBox(
              height: 30,
            ),
            //create convert button
            ElevatedButton(
              onPressed: () {
                //on pressing the convert we
                //should convert the inr to dollar
                setState(() {
                  dollar = double.parse(inrController.text) * 0.012;
                });
              },
              child: Text("Convert"),
            ),
            //for some space between button and text
            SizedBox(
              height: 30,
            ),
            //now we have to show dollar on screen
            //so we will use here text widget
            Text(
              "Dollar : " + dollar.toString(),
              //increse some font size
              style: TextStyle(
                fontSize: 30,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

dollar_to_inr.dart

import 'package:flutter/src/widgets/framework.dart';
import 'package:flutter/src/widgets/placeholder.dart';
import 'package:flutter/material.dart';

class DollarToINR extends StatefulWidget {
  const DollarToINR({super.key});

  @override
  State<DollarToINR> createState() => _DollarToINRState();
}

class _DollarToINRState extends State<DollarToINR> {
  //create controller for dollar
  TextEditingController dollarController = TextEditingController();
  //creating the varibale to store the inr value
  double inr = 0.0;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Dollar to inr Converter'),
      ),
      body: Container(
        //give some padding
        padding: EdgeInsets.all(20),
        //here we need to create
        //one text filed to take input form user
        //and one button
        //so we will use here column widget
        child: Column(
          children: [
            TextField(
              controller: dollarController,
              //some box around text field
              decoration: const InputDecoration(
                border: OutlineInputBorder(),
                //labele text
                labelText: 'Enter Dollar',
              ),
            ),
            //need some space between
            //textfield and button
            const SizedBox(
              height: 30,
            ),
            //create convert button
            ElevatedButton(
              onPressed: () {
                //on pressing the convert we
                //should convert the inr to dollar
                setState(() {
                  inr = double.parse(dollarController.text) * 82.40;
                });
              },
              child: Text("Convert"),
            ),
            //for some space between button and text
            SizedBox(
              height: 30,
            ),
            //now we have to show dollar on screen
            //so we will use here text widget
            Text(
              "Inr : " + inr.toString(),
              //increse some font size
              style: TextStyle(
                fontSize: 30,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Step-by-step process