readme.md

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main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Slivers',
      theme: ThemeData.light(),
      darkTheme: ThemeData.dark(),
      themeMode: ThemeMode.system,
      home: const Page(),
    );
  }
}

class Page extends StatelessWidget {
  const Page({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: <Widget>[
          SliverList(
            delegate: SliverChildBuilderDelegate(
              (context, index) => BuildNotifyingWidget(
                "Sliver list builder",
                child: Text("Sliver list builder $index"),
              ),
              childCount: 50,
            ),
          ),
          SliverList(
            delegate: SliverChildBuilderDelegate(
              (context, index) => BuildNotifyingWidget(
                "Sliver list builder 2",
                child: Text("Sliver list builder 2 $index"),
              ),
              childCount: 50,
            ),
          ),
          SliverList(
            delegate: SliverChildListDelegate(
              List.generate(
                50,
                (index) => BuildNotifyingWidget(
                  "Sliver list",
                  child: Text("Sliver list $index"),
                ),
              ).toList(),
            ),
          ),
          SliverToBoxAdapter(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: List.generate(
                50,
                (index) => BuildNotifyingWidget(
                  "SliverToBoxAdapter",
                  child: Text("SliverToBoxAdapter $index"),
                ),
              ),
            ),
          )
        ],
      ),
    );
  }
}

class BuildNotifyingWidget extends StatelessWidget {
  final String prefix;
  final Widget child;

  BuildNotifyingWidget(this.prefix, {required this.child, Key? key})
      : super(key: key) {
    print("creating object from $prefix ($child)");
  }

  @override
  Widget build(BuildContext context) {
    print("building from $prefix ($child)");
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: SizedBox(
        height: 50,
        child: child,
      ),
    );
  }
}