AnimatedContainer是Flutter中的一个Widget，它能够在一定时间内将容器的属性例如颜色、大小等进行平滑的过渡动画效果。

代码示例：

import 'package:flutter/material.dart';

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
  double _width = 100.0;
  double _height = 100.0;
  Color _color = Colors.blue;
  double _borderRadius = 10.0;

  void _changeProperties() {
    setState(() {
      _width = 200.0;
      _height = 200.0;
      _color = Colors.red;
      _borderRadius = 30.0;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('AnimatedContainer'),
      ),
      body: Center(
        child: GestureDetector(
          onTap: () {
            _changeProperties();
          },
          child: AnimatedContainer(
            duration: Duration(seconds: 1),
            width: _width,
            height: _height,
            decoration: BoxDecoration(
              color: _color,
              borderRadius: BorderRadius.circular(_borderRadius),
            ),
          ),
        ),
      ),
    );
  }
}