main.dart

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

void main() => runApp(MaterialApp(
        home: Scaffold(
      appBar: AppBar(
        title: Text('AnimatedContainer Demo'),
      ),
      body: Center(child: Highlight(child: Text('123123123122312312'))),
    )));

class Highlight extends StatefulWidget {
  Highlight({this.child});
  final Widget child;
  @override
  _HighlightState createState() => _HighlightState(child: child);
}

class _HighlightState extends State<Highlight> {
  _HighlightState({this.child});

  Color _color = Colors.green;
  final Widget child;

  @override
  void initState() {
    super.initState();
    Timer(
      const Duration(seconds: 3),
      () => setState(
        () {
          _color = null;
        },
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return AnimatedContainer(
      child: FlatButton(child: child, onPressed: () {}),
      // Use the properties stored in the State class.
      decoration: BoxDecoration(
        color: _color,
      ),
      // Define how long the animation should take.
      duration: Duration(seconds: 1),
      // Provide an optional curve to make the animation feel smoother.
      curve: Curves.fastOutSlowIn,
    );
  }
}