flutter splash screen

splashScreen.dart

void main() async{
  runApp(
    new MaterialApp(
      title: "weather app",
      debugShowCheckedModeBanner: false,
      theme: ThemeData.light(),
      home: new SplashScreen(),
      routes: <String, WidgetBuilder>{
        '/HomePage': (BuildContext context) =>  HomePage(),
      },
    ),
  );
}

class SplashScreen extends StatefulWidget {
  @override
  _SplashScreenState createState() => new _SplashScreenState();
}

class _SplashScreenState extends State<SplashScreen> {
  startTime() async {
    var _duration = new Duration(seconds: 2);
    return new Timer(_duration, navigationPage);
  }
  void navigationPage() {
    Navigator.of(context).pushReplacementNamed('/HomePage');
  }

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

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: Container(
        width: MediaQuery.of(context).size.width,
        height: MediaQuery.of(context).size.height,
        child: new Image.asset('الصورة من ملف الاسيت',fit: BoxFit.cover,),
      ),
    );
  }
}