samples/infinite_list/lib/main.dart

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:io' show Platform;

import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:window_size/window_size.dart';

import 'src/api/item.dart';
import 'src/catalog.dart';
import 'src/item_tile.dart';

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

const double windowWidth = 480;
const double windowHeight = 854;

void setupWindow() {
  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
    WidgetsFlutterBinding.ensureInitialized();
    setWindowTitle('Infinite List');
    setWindowMinSize(const Size(windowWidth, windowHeight));
    setWindowMaxSize(const Size(windowWidth, windowHeight));
    getCurrentScreen().then((screen) {
      setWindowFrame(Rect.fromCenter(
        center: screen!.frame.center,
        width: windowWidth,
        height: windowHeight,
      ));
    });
  }
}

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

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<Catalog>(
      create: (context) => Catalog(),
      child: MaterialApp(
        title: 'Infinite List Sample',
        theme: ThemeData.light(),
        home: const MyHomePage(),
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Infinite List Sample'),
      ),
      body: Selector<Catalog, int?>(
        // Selector is a widget from package:provider. It allows us to listen
        // to only one aspect of a provided value. In this case, we are only
        // listening to the catalog's `itemCount`, because that's all we need
        // at this level.
        selector: (context, catalog) => catalog.itemCount,
        builder: (context, itemCount, child) => ListView.builder(
          // When `itemCount` is null, `ListView` assumes an infinite list.
          // Once we provide a value, it will stop the scrolling beyond
          // the last element.
          itemCount: itemCount,
          padding: const EdgeInsets.symmetric(vertical: 18),
          itemBuilder: (context, index) {
            // Every item of the `ListView` is individually listening
            // to the catalog.
            var catalog = Provider.of<Catalog>(context);

            // Catalog provides a single synchronous method for getting the
            // current data.
            return switch (catalog.getByIndex(index)) {
              Item(isLoading: true) => const LoadingItemTile(),
              var item => ItemTile(item: item)
            };
          },
        ),
      ),
    );
  }
}