Advanced Flutter Motion: Physics, Implicit Animations & Custom Painters

import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';

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

  @override
  State<SpringCard> createState() => _SpringCardState();
}

class _SpringCardState extends State<SpringCard> with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  Alignment _dragAlignment = Alignment.center;

  final _spring = const SpringDescription(
    mass: 1.0,
    stiffness: 350.0,
    damping: 24.0,
  );

  @override
  void initState() {
    super.initState();
    _controller = AnimationController.unbounded(vsync: this);
  }

  void _runSpring(Offset pixelsPerSecond, Size size) {
    final simulation = SpringSimulation(_spring, _dragAlignment.x, 0.0, -pixelsPerSecond.dx / size.width);
    _controller.animateWith(simulation);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanUpdate: (details) {
        setState(() {
          _dragAlignment += Alignment(
            details.delta.dx / (context.size!.width / 2),
            details.delta.dy / (context.size!.height / 2),
          );
        });
      },
      onPanEnd: (details) => _runSpring(details.velocity.pixelsPerSecond, context.size!),
      child: Align(
        alignment: _dragAlignment,
        child: const Card(child: SizedBox(width: 200, height: 280)),
      ),
    );
  }
}