https://i-doctor.sakura.ne.jp/font/?p=42233

flutter-web_firestore_list

import 'package:flutter/material.dart';
import 'package:firebase/firebase.dart';
import 'package:firebase/firestore.dart' as fs;

void main() {
  initializeApp(
    apiKey: "YourApiKey",
    authDomain: "YourAuthDomain",
    databaseURL: "YourDatabaseUrl",
    projectId: "YourProjectId",
    storageBucket: "YourStorageBucket");
  );

  //fs.Firestore store = firestore();
  //fs.CollectionReference ref = store.collection("kasikari-memo");

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final fs.Firestore store = firestore();
  final List<Map<String, dynamic>> messages = List();
  final List<Map<String, dynamic>> kasikarimemo = List();

  fetchMessages() async {
    var messagesRef = await store.collection('messages').get();
    var memosRef = await store.collection('kasikarimemo').get();

    messagesRef.forEach(
      (doc) {
        messages.add(doc.data());
      },
    );

    memosRef.forEach(
      (doc) {
        kasikarimemo.add(doc.data());
      },
    );

    setState(() {});
  }

  @override
  void initState() {
    super.initState();
    fetchMessages();
  }

  @override
  Widget build(BuildContext context) {
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          var m = Map<String, String>();
          m['content'] = 'hogehoge';
          await store.collection('messages').add(m);
          setState(() {
            messages.add(m);
          });
        },
        child: Icon(Icons.add),
      ),
      
      body: ListView(
        children: kasikarimemo.map(
          (message) {
            return Card(
              child: ListTile(
                leading: FlutterLogo(size: 72.0),
                title: Text(message['borrowOrLend']),
                subtitle: Text(message['stuff']),
                isThreeLine: true,
              ),
            );
          },
        ).toList(),
      )
      
    );
  }
}