Чтобы анимировать значок QR во Flutter, вы можете использовать различные методы. Вот несколько примеров кода:

Метод 1: AnimatedContainer

import 'package:flutter/material.dart';
class AnimatedQRIcon extends StatefulWidget {
  @override
  _AnimatedQRIconState createState() => _AnimatedQRIconState();
}
class _AnimatedQRIconState extends State<AnimatedQRIcon>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 1),
      vsync: this,
    )..repeat(reverse: true);
    _animation = Tween<double>(begin: 0.0, end: 1.0).animate(_controller);
  }
  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    return Center(
      child: AnimatedBuilder(
        animation: _animation,
        builder: (context, child) {
          return Transform.rotate(
            angle: _animation.value * 2 * 3.14159,
            child: Icon(Icons.qr_code),
          );
        },
      ),
    );
  }
}
// Usage
AnimatedQRIcon()

Метод 2: CustomPainter

import 'package:flutter/material.dart';
class AnimatedQRIcon extends StatefulWidget {
  @override
  _AnimatedQRIconState createState() => _AnimatedQRIconState();
}
class _AnimatedQRIconState extends State<AnimatedQRIcon>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  double _rotation = 0.0;
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 1),
      vsync: this,
    )..repeat(reverse: true);
    _controller.addListener(() {
      setState(() {
        _rotation = _controller.value * 2 * 3.14159;
      });
    });
  }
  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
```dart
  @override
  Widget build(BuildContext context) {
    return Center(
      child: CustomPaint(
        painter: _QRPainter(rotation: _rotation),
        child: Icon(Icons.qr_code),
      ),
    );
  }
}

class _QRPainter extends CustomPainter {
  final double rotation;

  _QRPainter({this.rotation});

  @override
  void paint(Canvas canvas, Size size) {
    canvas.rotate(rotation);
    // draw QR code here
  }

  @override
  bool shouldRepaint(_QRPainter oldDelegate) {
    return oldDelegate.rotation != rotation;
  }
}
// Usage
AnimatedQRIcon()

Это всего лишь пара примеров анимации QR-значка во Flutter. Вы можете дополнительно настроить анимацию в соответствии со своими требованиями.