Pulsing scale animation

main.dart

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with SingleTickerProviderStateMixin {
  late AnimationController _animation;
  late Animation<double> _radius;
  late Animation<double> _iconRadius;

  static double radius = 48;
  static double iconRadius = 24;

  @override
  void initState() {
    super.initState();
    _animation = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 1200),
    );

    _radius =
        Tween<double>(end: radius, begin: radius * 1.56).animate(_animation);
    _iconRadius = Tween<double>(end: iconRadius, begin: iconRadius * 1.56)
        .animate(_animation);
    _animation.addStatusListener((status) {
      if (status == AnimationStatus.completed) {
        _animation.reset();
      } else if (status == AnimationStatus.dismissed) {
        _animation.forward();
      }
    });

    _animation.forward();
  }

  @override
  void dispose() {
    _animation.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: AnimatedBuilder(
            animation: _animation,
            builder: (context, child) {
              return Container(
                height: _radius.value,
                width: _radius.value,
                decoration: BoxDecoration(
                  shape: BoxShape.circle,
                  color: Colors.purple,
                  boxShadow: [
                    BoxShadow(
                        color: Colors.purpleAccent.withOpacity(0.2),
                        spreadRadius: 10,
                        blurRadius: 3),
                  ],
                ),
                alignment: Alignment.center,
                child: Icon(Icons.mic_outlined, size: _iconRadius.value),
              );
            },
          ),
        ),
      ),
    );
  }
}