ASYNC AND AWAIT IN FLUTTER

main.dart

import 'package:flutter/material.dart';
import 'dart:async';

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',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: AsyncAwait(),
    );
  }
}

class AsyncAwait extends StatefulWidget {
  @override
  _AsyncAwaitState createState() => _AsyncAwaitState();
}

class _AsyncAwaitState extends State<AsyncAwait> {
  bool _isLoading = false;

  void _asyncAction() async {
    setState(() => _isLoading = true);

    await Future.delayed(Duration(seconds: 5));

    setState(() => _isLoading = false);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Async and Await example")),
      body: Center(
        child: _isLoading
            ? CircularProgressIndicator()
            : RaisedButton(
                child: Text("Start Asyncronous action"),
                color: Colors.red,
                onPressed: _asyncAction,
              ),
      ),
    );
  }
}