sliver_app_bar_title 1.0.1+7

SliverAppBarTitle is a widget that can be used to show a title on pinned SliverAppBar based on scrolling and particular widget

example/lib/main.dart

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

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final globalKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: [
          SliverAppBar(
            pinned: true,
            title: SliverAppBarTitle(
              targetWidgetKey: globalKey,
              duration: const Duration(milliseconds: 100),
              child: const Text("Number 2 is hidden"),
            ),
            expandedHeight: 256,
          ),
          SliverList(
              delegate: SliverChildBuilderDelegate(
            (BuildContext context, int index) {
              return Container(
                color: index.isOdd ? Colors.white : Colors.black12,
                height: 100.0,
                child: Center(
                  child: Text('$index',
                      key: index == 2 ? globalKey : null, textScaleFactor: 5),
                ),
              );
            },
            childCount: 20,
          ))
        ],
      ),
    );
  }
}