如何在颤动中动画隐藏AppBar？

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

class AnimatedAppBar extends StatefulWidget {
  @override
  _AnimatedAppBarState createState() => _AnimatedAppBarState();
}

class _AnimatedAppBarState extends State<AnimatedAppBar>
    with SingleTickerProviderStateMixin {
  ScrollController _scrollController;
  AnimationController _animationController;
  bool _isVisible = true;

  @override
  void initState() {
    super.initState();
    _scrollController = ScrollController();
    _animationController = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 300),
    );
    _scrollController.addListener(_handleScroll);
  }

  @override
  void dispose() {
    _scrollController.dispose();
    _animationController.dispose();
    super.dispose();
  }

  void _handleScroll() {
    if (_scrollController.position.userScrollDirection ==
            ScrollDirection.reverse &&
        _scrollController.position.pixels > 100) {
      if (_isVisible) {
        _isVisible = false;
        _animationController.reverse();
      }
    }
    if (_scrollController.position.userScrollDirection ==
            ScrollDirection.forward &&
        !_isVisible) {
      _isVisible = true;
      _animationController.forward();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: PreferredSize(
        preferredSize: Size.fromHeight(56.0),
        child: AnimatedBuilder(
          animation: _animationController,
          builder: (BuildContext context, Widget child) {
            return AppBar(
              title: Text('Animated AppBar'),
              elevation: _animationController.value * 4.0,
              backgroundColor: Colors.blue,
              automaticallyImplyLeading: false,
              toolbarHeight: 56.0 * _animationController.value,
            );
          },
        ),
      ),
      body: ListView.builder(
        controller: _scrollController,
        itemCount: 100,
        itemBuilder: (BuildContext context, int index) {
          return ListTile(
            title: Text('Item $index'),
          );
        },
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: AnimatedAppBar(),
  ));
}