flutter-AnimationControllerを使う

import 'package:fluro/fluro.dart';
import 'package:flutter/material.dart';
import 'dart:math' as math;
class AnimatedDemo extends StatefulWidget {
 static const String sName = 'animatedDemo';
 @override
 _AnimatedDemoState createState() => _AnimatedDemoState();
}
class _AnimatedDemoState extends State<AnimatedDemo>
 with TickerProviderStateMixin {
 AnimationController animationController;
 Animation animation;
 @override
 void initState() {
 // TODO: implement initState
 super.initState();
 animationController =
 AnimationController(vsync: this, duration: Duration(seconds: 2))
 ..addStatusListener((status) {
 if (status == AnimationStatus.completed) {
 animationController.reverse();
 } else if (status == AnimationStatus.dismissed) {
 animationController.forward();
 }
 });
 animation =
 Tween(begin: 0.0, end: 2.0 * math.pi).animate(animationController);
 animationController.forward();
 }
 @override
 void dispose() {
 // TODO: implement dispose
 super.dispose();
 animationController.dispose();
 }
 @override
 Widget build(BuildContext context) {
 return Scaffold(
 appBar: AppBar(title: Text('animated_demo')),
 body: AnimatedBuilder(
 animation: animation,
 builder: (BuildContext context, Widget child) {
 return Transform.rotate(angle: animation.value, child: child);
 },
 child: FlutterLogo(size: 60,),
 ),
 );
 }
}