example.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Launch Screen', theme: ThemeData(), home: MyHome());
  }
}

class Screen2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(child: Text("Hello world!"));
  }
}

class MyHome extends StatefulWidget {
  const MyHome({ Key key }) : super(key: key);

  @override
  _MyHomeState createState() => _MyHomeState();
}

class _MyHomeState extends State<MyHome> {

  bool isLoading = true;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Launch Screen',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text("Launch Screen"),
        ),
        body: Container(
          child: isLoading
              ? Center(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Text("Loading..."),
                      RaisedButton(
                        child: Text("Press me!"),
                        onPressed: () => setState(
                          () => isLoading = false
                        )
                      )
                    ]
                  ),
                )
              : Screen2(),
        ),
      ),
    );
  }
}