Flutter - The Hero Animation - YouTube episode source code...

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(new MyApp());
}

/// Root MaterialApp
class MyApp extends StatelessWidget {
  var _routes = <String, WidgetBuilder>{
    "/anotherPage": (BuildContext context) =>
    new AnotherPage(title: "Another Page"),
  };

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Home Page'),
      routes: _routes,
    );
  }
}

/// place: "/"
class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    // llama Image
    var decoratedBox = new DecoratedBox(
        decoration: new BoxDecoration(
          image: new DecorationImage(
            fit: BoxFit.fitWidth,
            image: new AssetImage('images/llama.png'),
          ),
          shape: BoxShape.circle,
        )
    );

    // hero top left
    var hero = new Hero(
      tag: 'hero-tag-llama',
      child: decoratedBox,
    );

    var _children = <Widget>[
      new Container(
        height: 50.0,
        width: 50.0,
        child: hero,
      ),
    ];

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Column(children: _children),
      floatingActionButton: new FloatingActionButton(
        onPressed: _onPressed,
        tooltip: 'Increment',
        child: new Icon(Icons.done),
      ),);
  }

  void _onPressed() {
    Navigator.of(context).pushNamed("/anotherPage");
  }
}


// place: "/anotherPage"
class AnotherPage extends StatefulWidget {
  AnotherPage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _AnotherPageState createState() => new _AnotherPageState();
}

class _AnotherPageState extends State<AnotherPage> {
  @override
  Widget build(BuildContext context) {
    // llama Image
    var decoratedBox = new DecoratedBox(
        decoration: new BoxDecoration(
          image: new DecorationImage(
            fit: BoxFit.fitWidth,
            image: new AssetImage('images/llama.png'),
          ),
          shape: BoxShape.circle,
        )
    );

    // hero center
    var hero = new Hero(
      tag: 'hero-tag-llama',
      child: decoratedBox,
    );

    var center = new Center(
      child: new Container(
        height: 100.0,
        width: 100.0,
        child: hero,
      ),);

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: center,
    );
  }
}

The Youtube episode: https://youtu.be/0oq6Ofh2WNg