如何在Flutter中设置自定义AppBar动画？

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

class CustomAppBar extends StatefulWidget {
  @override
  _CustomAppBarState createState() => _CustomAppBarState();
}

class _CustomAppBarState extends State<CustomAppBar> {
  // 定义AppBar的高度
  double appBarHeight = 100.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: <Widget>[
          SliverAppBar(
            expandedHeight: appBarHeight,
            flexibleSpace: FlexibleSpaceBar(
              background: Container(
                // 添加你想要的自定义AppBar内容
                child: Text('Custom AppBar'),
              ),
            ),
          ),
          // 添加其他内容
        ],
      ),
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: CustomAppBar(),
    );
  }
}