我正在制作一个笔记应用程序，NotesView 会清除所有其他笔记并将其替换为我最近的笔记

Question

这是 NotesView：

import 'package:app_two/lib/constants/routes.dart';
import 'package:app_two/lib/enums/menu_action.dart';
import 'package:app_two/lib/services/auth/auth_service.dart';
import 'package:app_two/lib/services/auth/crud/notes_service.dart';
import 'package:flutter/material.dart';

class NotesView extends StatefulWidget {
  const NotesView({super.key});

  @override
  State<NotesView> createState() => _NotesViewState();
}

class _NotesViewState extends State<NotesView> {
  late Future _myFuture;
  late final NotesService _notesService;
  String get userEmail => AuthService.firebase().currentUser!.email!;

  @override
  void initState() {
    super.initState();
    _notesService = NotesService();
    _myFuture = getGet();
  }

  // @override //delete
  // void dispose() {
  //   _notesService.close();
  //   super.dispose();
  // }

  getGet() async {
    return await _notesService.getOrCreateUser(email: userEmail);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Your Notes'),
        actions: [
          IconButton(
            onPressed: () {
              Navigator.of(context).pushNamed(newNoteRoute);
            },
            icon: const Icon(Icons.add),
          ),
          PopupMenuButton<MenuAction>(
            onSelected: (value) async {
              switch (value) {
                case MenuAction.logout:
                  final shouldLogout = await showLogOutDialog(context);
                  if (shouldLogout) {
                    await AuthService.firebase().logOut();
                    Navigator.of(context).pushNamedAndRemoveUntil(
                      loginRoute,
                      (_) => false,
                    );
                  }
              }
            },
            itemBuilder: (context) {
              return const [
                PopupMenuItem<MenuAction>(
                  value: MenuAction.logout,
                  child: Text('Logout'),
                ),
              ];
            },
          )
        ],
      ),
      body: FutureBuilder(
        future: _myFuture,
        builder: (context, snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.done:
              return StreamBuilder(
                stream: _notesService.allNotes,
                builder: (context, snapshot) {
                  switch (snapshot.connectionState) {
                    case ConnectionState.waiting:
                    case ConnectionState.active:
                      if (snapshot.hasData) {
                        final allNotes = snapshot.data as List<DatabaseNote>;
                        return ListView.builder(
                          itemCount: allNotes.length,
                          itemBuilder: (context, index) {
                            final note = allNotes[index];
                            return ListTile(
                              title: Text(
                                note.text,
                                maxLines: 1,
                                softWrap: true,
                                overflow: TextOverflow.ellipsis,
                              ),
                            );
                          },
                        );
                      } else {
                        return const CircularProgressIndicator();
                      }
                    default:
                      return const CircularProgressIndicator();
                  }
                },
              );
            default:
              return const CircularProgressIndicator();
          }
        },
      ),
    );
  }

  Future<bool> showLogOutDialog(BuildContext context) {
    return showDialog<bool>(
      context: context,
      builder: (context) {
        return AlertDialog(
          title: const Text('Sign out'),
          content: const Text('Are you sure you want to sign out?'),
          actions: [
            TextButton(
                onPressed: () {
                  Navigator.of(context).pop(false);
                },
                child: const Text('Cancel')),
            TextButton(
                onPressed: () {
                  Navigator.of(context).pop(true);
                },
                child: const Text('Logout'))
          ],
        );
      },
    ).then((value) => value ?? false);
  }
}


//Notes_service

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart' show join;
import 'crud_exceptions.dart';

class NotesService {
  Database? _db;

  List<DatabaseNote> _notes = [];

  static final NotesService _shared = NotesService._sharedInstance();
  NotesService._sharedInstance() {
    _notesStreamController = StreamController<List<DatabaseNote>>.broadcast(
      onListen: () {
        _notesStreamController.sink.add(_notes);
        //populate stream with a stream of notes that we've already read from the database
      },
    );
  }
  factory NotesService() => _shared; //singleton

  late final StreamController<List<DatabaseNote>> _notesStreamController;

  Stream<List<DatabaseNote>> get allNotes => _notesStreamController.stream;

  Future<DatabaseUser?> getOrCreateUser({required String email}) async {
    try {
      final user = await getUser(email: email);
      return user;
    } on CouldNotFindUser {
      final createdUser = await createUser(email: email);
      return createdUser;
    } on DatabaseIsNotOpen {
      open();
    } catch (e) {
      print(e.toString());
      rethrow;
    }
  }

  Future<void> _cacheNotes() async {
    final allNotes = await getAllNotes();
    _notes = allNotes.toList();
    _notesStreamController.add(_notes);
  }

  Future<DatabaseNote> updateNote({
    required DatabaseNote note,
    required String text,
  }) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    //make sure note exists
    await getNote(id: note.id);
    //update db
    final updatesCount = await db.update(noteTable, {
      textColumn: text,
      isSyncedwithCloudColumn: 0,
    });
    if (updatesCount == 0) {
      throw CouldNotUpdateNote();
    } else {
      final updatedNote = await getNote(id: note.id);
      _notes.removeWhere((note) => note.id == updatedNote.id);
      _notes.add(updatedNote);
      _notesStreamController.add(_notes);
      return updatedNote;
    }
  }

  Future<Iterable<DatabaseNote>> getAllNotes() async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final notes = await db.query(noteTable);

    return notes.map((noteRow) => DatabaseNote.fromRow(noteRow));
  }

  Future<DatabaseNote> getNote({required int id}) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final notes = await db.query(
      noteTable,
      limit: 1,
      where: 'id = ?',
      whereArgs: [id],
    );
    if (notes.isEmpty) {
      throw CouldNotFindNote();
    } else {
      final note = DatabaseNote.fromRow(notes.first);
      _notes.removeWhere((note) => note.id == id);
      _notesStreamController.add(_notes);
      return note;
    }
  }

  Future<int> deleteAllNotes() async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final numberOfdeletions = await db.delete(noteTable);
    _notes = [];
    _notesStreamController.add(_notes);
    return numberOfdeletions;
  }

  Future<void> deleteNote({required int id}) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final deletedCount = await db.delete(
      noteTable,
      where: 'id = ?',
      whereArgs: [id],
    );
    if (deletedCount == 0) {
      throw CouldNotDeleteNote();
    } else {
      _notes.removeWhere((note) => note.id == id);
      _notesStreamController.add(_notes);
    }
  }

  Future<DatabaseNote> createNote({required DatabaseUser owner}) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    //Make sure owner exists in database withthe correct id
    final dbUser = await getUser(email: owner.email);
    if (dbUser != owner) {
      throw CouldNotFindUser();
    }

    const text = '';
    //create the note
    final noteId = await db.insert(noteTable, {
      userIdColumn: owner.id,
      textColumn: text,
      isSyncedwithCloudColumn: 1,
    });

    final note = DatabaseNote(
      id: noteId,
      userId: owner.id,
      text: text,
      isSyncedWithCloud: true,
    );

    _notes.add(note);
    _notesStreamController.add(_notes);

    return note;
  }

  Future<DatabaseUser> getUser({required String email}) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final results = await db.query(
      userTable,
      limit: 1,
      where: 'email = ?',
      whereArgs: [email.toLowerCase()],
    );
    if (results.isEmpty) {
      throw CouldNotFindUser();
    } else {
      return DatabaseUser.fromRow(results.first);
    }
  }

  Future<DatabaseUser> createUser({required String email}) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    final results = await db.query(
      userTable,
      limit: 1,
      where: 'email = ?',
      whereArgs: [email.toLowerCase()],
    );
    if (results.isNotEmpty) {
      throw UserAlreadyExists();
    }
    final userId = await db.insert(userTable, {
      emailColumn: email.toLowerCase(),
    });

    return DatabaseUser(id: userId, email: email);
  }

  Future<void> deleteUser({required String email}) async {
    final db = _getDatabaseorThrow();
    final deletedCount = await db.delete(
      userTable,
      where: 'email = ?',
      whereArgs: [email.toLowerCase()],
    );
    if (deletedCount != 1) {
      throw CouldNotDeleteUser();
    }
  }

  Database _getDatabaseorThrow() {
    final db = _db;
    if (db == null) {
      throw DatabaseIsNotOpen();
    } else {
      return db;
    }
  }

  Future<void> close() async {
    final db = _db;
    if (db == null) {
      try {
        await open();
      } on DatabaseIsNotOpen {
        open();
      }
      // throw DatabaseIsNotOpen();
    } else {
      await db.close();
      _db = null;
    }
  }

  Future<void> _ensureDbIsOpen() async {
    if (_db != null) {
      try {
        await open();
      } on DatabaseAlreadyOpenException {
        //empty
      }
    }
  }

  Future<void> open() async {
    if (_db != null) {
      throw DatabaseAlreadyOpenException();
    }
    try {
      await _ensureDbIsOpen();
      final docsPath = await getApplicationDocumentsDirectory();
      final dbPath = join(docsPath.path, dbName);
      final db = await openDatabase(dbPath);
      _db = db;
      //create user table
      await db.execute(createUserTable);
      //create note table
      await db.execute(createNoteTable);
      await _cacheNotes();
    } on MissingPlatformDirectoryException {
      throw UnableToGetDocumentDirectory();
    }
  }
}

@immutable
class DatabaseUser {
  final int id;
  final String email;

  const DatabaseUser({
    required this.id,
    required this.email,
  });
  DatabaseUser.fromRow(Map<String, Object?> map)
      : id = map[idColumn] as int,
        email = map[emailColumn] as String;

  @override
  String toString() => 'Person, ID = $id, email= $email';

  @override
  bool operator ==(covariant DatabaseUser other) => id == other.id;

  @override
  int get hashCode => id.hashCode;
}

class DatabaseNote {
  final int id;
  final int userId;
  final String text;
  final bool isSyncedWithCloud;

  DatabaseNote({
    required this.id,
    required this.userId,
    required this.text,
    required this.isSyncedWithCloud,
  });

  DatabaseNote.fromRow(Map<String, Object?> map)
      : id = map[idColumn] as int,
        userId = map[userIdColumn] as int,
        text = map[textColumn] as String,
        isSyncedWithCloud =
            (map[isSyncedwithCloudColumn] as int) == 1 ? true : false;

  @override
  String toString() =>
      'Note, ID = $id, userId = $userId, isSyncedWithCloud = $isSyncedWithCloud, text = $text';

  @override
  bool operator ==(covariant DatabaseNote other) => id == other.id;

  @override
  int get hashCode => id.hashCode;
}

const dbName = 'notes.db';
const noteTable = 'note';
const userTable = 'user';
const idColumn = 'id';
const emailColumn = 'email';
const userIdColumn = 'user_id';
const textColumn = 'text';
const isSyncedwithCloudColumn = 'is_synced_with_cloud';
const createUserTable = '''CREATE TABLE IF NOT EXISTS "user" (
        "id"    INTEGER NOT NULL,
        "email" TEXT NOT NULL UNIQUE,
        PRIMARY KEY("id" AUTOINCREMENT)
        );''';
const createNoteTable = '''CREATE TABLE IF NOT EXISTS "note" (
          "id"  INTEGER NOT NULL,
          "user_id" INTEGER NOT NULL,
          "text"    TEXT,
          "is_synced_with_cloud"    INTEGER DEFAULT 0,
          FOREIGN KEY("user_id") REFERENCES "user"("id"),
          PRIMARY KEY("id" AUTOINCREMENT)
        );''';

我正在制作一个笔记应用程序，NotesView 会清除所有其他笔记并将其替换为我最近没有的笔记。我不知道为什么会这样

您输入的每个注释都应显示在图块上。但是却发生了这种情况： 但只有在我重新启动应用程序之后。在下图中，我添加了新注释，然后重新启动应用程序

我相信我在 StreamBuilder 中做了一些非常重要的事情，但不知道是什么。

如果有任何帮助，我将不胜感激。

Answer 1

尝试将

case ConnectionState.active

中的

case ConnectionState.done

更改为

StreamBuilder

。

由于在

case ConnectionState.active

中构建列表，可能会发生重复。

Answer 2

我不知道你的 db.update 做了什么，也不知道你的 SQL 查询是什么样的，但如果你不传递 id，你应该如何更新注释？

Future<DatabaseNote> updateNote({
    required DatabaseNote note,
    required String text,
  }) async {
    await _ensureDbIsOpen();
    final db = _getDatabaseorThrow();
    //make sure note exists
    await getNote(id: note.id);
    //update db
    final updatesCount = await db.update(noteTable, { ///how does magically know what note to update?
      textColumn: text,
      isSyncedwithCloudColumn: 0,
    });
    if (updatesCount == 0) {
      throw CouldNotUpdateNote();
    } else {
      final updatedNote = await getNote(id: note.id);
      _notes.removeWhere((note) => note.id == updatedNote.id);
      _notes.add(updatedNote);
      _notesStreamController.add(_notes);
      return updatedNote;
    }
  }

如果您使用 INSERT OR REPLACE INTO 因为您没有传递 id，那么您将创建一个新行而不是更新它，并且您的缓存列表会向您提供错误信息，因为最后您认为您正确更新了它并且只是用相同的 id 替换注释，您的缓存列表不再反映真实信息。

如果您因为 where 子句没有 id 而更新表中的所有注释，那么您将在重新启动时出现当前问题

检查你的数据库层，看看你是否真的在做你想做的事。

Answer 3

您需要更改 db.update 调用，以便它有一个指定注释 id 的 where 子句：

db.更新( 注释表， {textColumn：文本}， 其中：'id = ?', whereArgs: [note.id], );

Answer 4

我也在做同样的课程，并停留在第32章（在笔记视图中显示笔记）。你完成了课程吗？我需要一些指导。