favorite_circle.dart

import 'package:flutter/material.dart';

class FavoriteCircle extends StatelessWidget {
  const FavoriteCircle({
    Key key,
    @required this.size,
    @required this.percent,
  }) : super(key: key);

  final Size size;
  final double percent;

  @override
  Widget build(BuildContext context) {
    return Positioned(
      bottom: size.height * 0.10,
      right: 10,
      child: percent < 0.2
          ? TweenAnimationBuilder<double>(
              tween: percent < 0.17
                  ? Tween(begin: 1, end: 0)
                  : Tween(begin: 0, end: 1),
              duration: const Duration(milliseconds: 300),
              builder: (context, value, widget) {
                return Transform.scale(
                  scale: 1.0 - value,
                  child: CircleAvatar(
                    minRadius: 20,
                    backgroundColor: Colors.red[300],
                    child: Icon(
                      Icons.favorite,
                      color: Colors.red[900],
                    ),
                  ),
                );
              })
          : Container(),
    );
  }
}