import 'package:flutter/material.dart';

import 'dart:async';

enum Option {

  A, B, C

}

class SimpleDialogDemo extends StatefulWidget {

  @override

  _SimpleDialogDemoState createState() => _SimpleDialogDemoState();

}

class _SimpleDialogDemoState extends State<SimpleDialogDemo> {

  String _choice = 'Nothing';

  Future _openSimpleDialog() async {

    final option = await showDialog(

      context: context,

      builder: (BuildContext context) {

        return SimpleDialog(

          title: Text('SimpleDialog'),

          children: <Widget>[

            SimpleDialogOption(

              child: Text('Option A'),

              onPressed: () {

                Navigator.pop(context, Option.A);

              },

            ),

            SimpleDialogOption(

              child: Text('Option B'),

              onPressed: () {

                Navigator.pop(context, Option.B);

              },

            ),

            SimpleDialogOption(

              child: Text('Option C'),

              onPressed: () {

                Navigator.pop(context, Option.C);

              },

            ),

          ],

          elevation: 100.0,

        );

      }

    );

    switch (option) {

      case Option.A:

        setState(() {

          _choice = 'A';

        });

        break;

      case Option.B:

        setState(() {

          _choice = 'B';

        });

        break;

      case Option.C:

        setState(() {

          _choice = 'C';

        });

        break;

      default:

    }

  }

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text('SimpleDialogDemo'),

        elevation: 0.0,

      ),

      body: Container(

        padding: EdgeInsets.all(16.0),

        child: Column(

          mainAxisAlignment: MainAxisAlignment.center,

          children: <Widget>[

            Text('Your choice is: $_choice'),

            Row(

              mainAxisAlignment: MainAxisAlignment.center,

              children: <Widget>[

              ],

            ),

          ],

        ),

      ),

      floatingActionButton: FloatingActionButton(

        child: Icon(Icons.format_list_numbered),

        onPressed: _openSimpleDialog,

      ),

    );

  }

}