superellipse_crash.dart

import 'dart:async';

import 'package:flutter/material.dart';

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

class App extends StatelessWidget {
  const App({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(theme: ThemeData.dark(), home: Demo());
  }
}

class Demo extends StatefulWidget {
  const Demo({super.key});

  @override
  State<Demo> createState() => _DemoState();
}

class _DemoState extends State<Demo> {
  late BorderRadius _borderRadius;
  var _isCircular = false;

  @override
  void initState() {
    super.initState();
    
    _borderRadius = BorderRadius.vertical(top: Radius.circular(64.0));
    Timer.periodic(const Duration(milliseconds: 200), (_) => _toggleBorderRadius());
  }

  void _toggleBorderRadius() {
    if (_isCircular) {
      _borderRadius = BorderRadius.vertical(top: Radius.circular(64.0));
    } else {
      _borderRadius = BorderRadius.all(Radius.circular(64.0));
    }

    _isCircular = !_isCircular;
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: _toggleBorderRadius,
        child: Icon(Icons.refresh),
      ),
      body: Align(
        alignment: Alignment.center,
        child: AnimatedContainer(
          duration: Duration(milliseconds: 200),
          curve: Cubic(0.34, 0.80, 0.34, 1.00),
          width: double.infinity,
          height: 200.0,
          decoration: ShapeDecoration(
            color: Colors.red,
            shape: RoundedSuperellipseBorder(borderRadius: _borderRadius),
          ),
        ),
      ),
    );
  }
}