content: import 'package:flutter/material.dart';
  
  import 'dart:math';
  
  class AnimatedContainerPage extends StatefulWidget {
    @override
    _AnimatedContainerPageState createState() => _AnimatedContainerPageState();
  }
  
  class _AnimatedContainerPageState extends State<AnimatedContainerPage> {
  
    double _width  = 50.0;
    double _height = 50.0;
    Color  _color  = Colors.pink;
  
    BorderRadiusGeometry _borderRadius = BorderRadius.circular(8.0);
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text('Animated Container'),
        ),
        body: Center(
          child: AnimatedContainer(
            duration: Duration( seconds: 1 ),
            curve: Curves.fastOutSlowIn,
            width: _width,
            height: _height,
            decoration: BoxDecoration(
              borderRadius: _borderRadius,
              color: _color
            ),
          )
        ),
  
        floatingActionButton: FloatingActionButton(
          child: Icon( Icons.play_arrow ),
          onPressed: _cambiarForma,
        ),
  
      );
    }
  
    void _cambiarForma() {
  
      final random = Random();
  
      setState(() {
  
        _width  = random.nextInt(300).toDouble();
        _height = random.nextInt(300).toDouble();
        _color  = Color.fromRGBO(
          random.nextInt(255), 
          random.nextInt(255),
          random.nextInt(255),
          1);
  
        _borderRadius = BorderRadius.circular( random.nextInt(100).toDouble() );
        
      });
  
    }
  
  }