flutter_shuqi/lib/pages/bookshelf/bookshelf_cloud_widget.dart

import 'package:flutter/material.dart';
import 'package:shuqi/public.dart';

class BookshelfCloudWidget extends AnimatedWidget {
  final double width;
  BookshelfCloudWidget({required Animation<double> animation, required this.width}) : super(listenable: animation);

  @override
  Widget build(BuildContext context) {
    var width = Screen.width;
    final Animation<double> animation = listenable as Animation<double>;
    return Container(
      width: width,
      height: width * 0.73,
      child: Stack(
        alignment: AlignmentDirectional.bottomStart,
        children: <Widget>[
          Positioned(
            bottom: -30,
            child: Image.asset(
              'assets/img/bookshelf_cloud_0.png',
              fit: BoxFit.cover,
              width: width,
            ),
          ),
          Positioned(
            bottom: animation.value * -5,
            child: Opacity(
              opacity: animation.value,
              child: Image.asset(
                'assets/img/bookshelf_cloud_1.png',
                fit: BoxFit.cover,
                width: width,
              ),
            ),
          ),
          Positioned(
            bottom: (1 - animation.value) * -10,
            child: Opacity(
              opacity: animation.value,
              child: Image.asset(
                'assets/img/bookshelf_cloud_2.png',
                fit: BoxFit.cover,
                width: width,
              ),
            ),
          ),
          Positioned(
            bottom: (animation.value - 0.5).abs() * -15,
            child: Opacity(
              opacity: (1.0 - animation.value),
              child: Image.asset(
                'assets/img/bookshelf_cloud_3.png',
                fit: BoxFit.cover,
                width: width,
              ),
            ),
          ),
        ],
      ),
    );
  }
}