main.dart:

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      routes: <String, WidgetBuilder> {
          '/app': (_) => AppPage(),
        },
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: InkWell(
        child: Image.asset('images/7.jpg',fit: BoxFit.fill,),
        onTap: (){
          Navigator.pushNamed(context, "/app");
        },
      ),
    );
  }

  @override
  void initState() {
    super.initState();
    countDown();
  }

// 倒计时
  void countDown() {
    var _duration = Duration(seconds: 3);
    new Future.delayed(_duration, go2HomePage);
  }

  void go2HomePage() {
    Navigator.of(context).pushReplacementNamed('/app');
  }
}


app.dart

import 'package:flutter/material.dart';

class AppPage extends StatefulWidget {
  @override
  _AppPageState createState() => _AppPageState();
}

class _AppPageState extends State<AppPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.orange.shade100,
      body: Column(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
          ListTile(
            title: Text('hello world'),
            subtitle: Text('Love you so much the beautiful world'),
          ),
          ListTile(
            title: Text('hello world'),
            subtitle: Text('Love you so much the beautiful world'),
          ),
          ListTile(
            title: Text('hello world'),
            subtitle: Text('Love you so much the beautiful world'),
          ),
        ],
      ),
    );
  }
}