Flutter Animated AppBar

.dart

import 'package:flutter/material.dart';

class AnimatedAppBar extends StatefulWidget {
  final Widget? leading;
  final String title;
  final String bodyText;
  final Widget body;
  final Widget? floatingActionButton;
  final RefreshCallback? onRefresh;

  const AnimatedAppBar(
      {super.key,
      this.leading,
      required this.title,
      required this.body,
      required this.bodyText,
      this.onRefresh,
      this.floatingActionButton});

  @override
  State<AnimatedAppBar> createState() => _AnimatedAppBarState();
}

class _AnimatedAppBarState extends State<AnimatedAppBar> {
  final scrollController = ScrollController();
  double opacity = 0.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: widget.floatingActionButton,
      appBar: AppBar(
        leading: widget.leading,
        title: AnimatedOpacity(
            duration: const Duration(milliseconds: 1000),
            opacity: opacity,
            child: Text(widget.title)),
      ),
      body: NotificationListener<ScrollNotification>(
        onNotification: (notification) {
          if (notification.metrics.pixels > 40.0) {
            setState(() => opacity = 1.0);
          } else {
            setState(() => opacity = 0.0);
          }
          return true;
        },
        child: RefreshIndicator.adaptive( // You can remove the refresh indicator it is optional
          onRefresh: widget.onRefresh == null ? () async {} : widget.onRefresh!,
          child: SingleChildScrollView(
            child: Padding(
              padding: const EdgeInsets.symmetric(horizontal: 16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    widget.bodyText,
                    style:TextStyle(fontSize: 28, color: Colors.black, 
                     fontWeight: FontWeight.bold)),
                  widget.body //This should be a list of widgets
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}