使用Flutter和Dart更新背景位置

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

class BackgroundScreen extends StatefulWidget {
  @override
  _BackgroundScreenState createState() => _BackgroundScreenState();
}

class _BackgroundScreenState extends State<BackgroundScreen> {
  double _backgroundPosition = 0.0;

  void _updateBackgroundPosition(double newPosition) {
    setState(() {
      _backgroundPosition = newPosition;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          Positioned(
            top: _backgroundPosition,
            child: SvgPicture.asset(
              'assets/background.svg',
              width: MediaQuery.of(context).size.width,
              height: MediaQuery.of(context).size.height,
              fit: BoxFit.cover,
            ),
          ),
          GestureDetector(
            onVerticalDragUpdate: (details) {
              _updateBackgroundPosition(details.delta.dy);
            },
            child: Container(),
          ),
        ],
      ),
    );
  }
}