lord_lami.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

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

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

class _MyStatefulWidgetState extends State<MyStatefulWidget>
    with TickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;
  var opacityLevel = 0.0;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(milliseconds: 1500),
      vsync: this,
    );
    _animation = CurvedAnimation(
      parent: _controller,
      curve: Curves.linear,
    );

    Future.delayed(Duration(seconds: 1), () {
      setState(() {
        _controller.forward();
        opacityLevel = 1;
      });
    });
  }

  @override
  void dispose() {
    super.dispose();
    _controller.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
          child: Row(mainAxisAlignment: MainAxisAlignment.center, children: [
        Container(width: 50, height: 50, color: Colors.blue),
        AnimatedOpacity(
            child: SizeTransition(
              sizeFactor: _animation,
              axis: Axis.horizontal,
              axisAlignment: -1,
              child: Center(
                child: FlutterLogo(size: 200.0),
              ),
            ),
            opacity: opacityLevel,
            duration: Duration(seconds: 2))
      ])),
    );
  }
}