How To Create Default Optional Arguments Using Flutter App

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  void  getArea(int height, [int width = 50]) {

    print( height * width  );

  }

  @override
  Widget build(BuildContext context) {
    return  Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.indigo,
        title: Text('Default Optional Arguments'),
      ),
            body: Center(
                child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Container(
                          margin: const EdgeInsets.fromLTRB(20, 10, 20, 10),
                          child:
                          RaisedButton(
                            onPressed: () => getArea(2),
                            child: Text(' Find Area Using Height '),
                            textColor: Colors.white,
                            color: Colors.lightBlue,
                            padding: EdgeInsets.fromLTRB(12, 12, 12, 12),
                          )
                      ),

                      Container(
                          margin: const EdgeInsets.fromLTRB(20, 10, 20, 10),
                          child:
                          RaisedButton(
                            onPressed: () => getArea(2, 10),
                            child: Text(' Find Area Using Both Height Width '),
                            textColor: Colors.white,
                            color: Colors.green,
                            padding: EdgeInsets.fromLTRB(12, 12, 12, 12),
                          )
                      ),

                    ])
            )
    );
  }
}