import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Implicit Animations')),
        body: ImplicitAnimationExample(),
      ),
    );
  }
}

class ImplicitAnimationExample extends StatefulWidget {
  @override
  _ImplicitAnimationExampleState createState() => _ImplicitAnimationExampleState();
}

class _ImplicitAnimationExampleState extends State<ImplicitAnimationExample> {
  bool _toggled = false;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: GestureDetector(
        onTap: () {
          setState(() {
            _toggled = !_toggled;
          });
        },
        child: AnimatedContainer(
          width: _toggled ? 200 : 100,
          height: _toggled ? 200 : 100,
          color: _toggled ? Colors.blue : Colors.red,
          alignment: _toggled ? Alignment.center : AlignmentDirectional.topCenter,
          duration: Duration(seconds: 1),
          curve: Curves.easeInOut,
          child: FlutterLogo(size: 75),
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Explicit Animations')),
        body: ExplicitAnimationExample(),
      ),
    );
  }
}

class ExplicitAnimationExample extends StatefulWidget {
  @override
  _ExplicitAnimationExampleState createState() => _ExplicitAnimationExampleState();
}

class _ExplicitAnimationExampleState extends State<ExplicitAnimationExample> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 2),
      vsync: this,
    )..repeat(reverse: true);

    _animation = Tween<double>(begin: 0, end: 300).animate(_controller)
      ..addListener(() {
        setState(() {});
      });
  }

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

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Container(
        margin: EdgeInsets.symmetric(vertical: 10),
        height: _animation.value,
        width: _animation.value,
        child: FlutterLogo(),
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:lottie/lottie.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Lottie Animations')),
        body: LottieAnimationExample(),
      ),
    );
  }
}

class LottieAnimationExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Lottie.asset('assets/animation.json'),
    );
  }
}