Error database_closed when using flutter's sqflite - sqlite

Question

I try to use sqflite to save some data like my class Movie but when i try to insert or query on the database, see this message:
[ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: DatabaseException(error database_closed)
my MovieBloc class:
List<Movie> _movies = new List<Movie> ();
class MoviesBloc implements BaseBloc {
final _moviesController = StreamController<List<Movie>>();
Database moviesDB;
String _moviesPath;
Stream<List<Movie>> get moviesStream => _moviesController.stream;
List<Movie> get movies => _movies;
int getLengthMovieList() {
return _movies.length;
}
clearMovieList() {
_movies.clear();
}
Future<void> openMovieDB({String dbName:'movies.db'}) async {
var databasesPath = await getDatabasesPath();
_moviesPath = join(databasesPath, dbName);
moviesDB = await openDatabase(_moviesPath, version: 1,
onCreate: (Database db, int version) async {
await db.execute(
'CREATE TABLE movies (Id INTEGER PRIMARY KEY AUTOINCREMENT, Title TEXT NOT NULL, imdbRating TEXT, Poster TEXT, Plot TEXT, Saved INTEGER DEFAULT 0)');
});
}
Future<void> closeMovieDB() async => moviesDB.close();
void dispose() {
_moviesController.close();
}
}
my MovieProvider class:
class MovieProvider extends MoviesBloc {
String _tableName = 'movies';
Future<Movie> insert(Movie movie, {conflictAlgorithm: ConflictAlgorithm.ignore}) async {
await moviesDB.insert(_tableName, movie.toMap(), conflictAlgorithm: conflictAlgorithm);
return movie;
}
Future<bool> insertAll(List<Movie> movies) async {
await Future.wait(movies.map((movie) async {
await this.insert(movie);
}
));
return true;
}
Future<List<Movie>> paginate(int page, {int limit: 15}) async {
print('in Paginate to SQLite');
List<Map> maps = await moviesDB.query(_tableName,
columns: ['Id', 'Title', 'imdbRating', 'Poster', 'Plot', 'Saved'],
limit: limit,
offset: page == 1 ? 0 : ((page -1) * limit)
);
List<Movie> movies = new List<Movie> ();
if (maps.length > 0) {
maps.map((movie) {
movies.add(Movie.fromJson(movie));
}
);
}
return movies;
}
}
my save method to sqflite:
static Future<bool> saveAllMoviesIntoSqlite(List<Movie> movies) async {
var db = new MovieProvider();
await db.openMovieDB();
await db.insertAll(movies);
await db.closeMovieDB();
return true;
}
my load method from sqflite:
static Future<Map> getAllMoviesFromSqlite(int page) async {
var db = new MovieProvider();
await db.openMovieDB();
List<Movie> movies = new List<Movie> ();
movies = await db.paginate(page);
await db.closeMovieDB();
return {
"currentPage": page,
"movies": movies
};
}
I observe that in insertAll method from MovieProvider class for insert any movie from the movies list to sq with await and async:
Future<bool> insertAll(List<Movie> movies) async {
await Future.wait(movies.map((movie) async {
await this.insert(movie);
}
));
return true;
}
I try to close and open database sometimes sequential and other plays with close and open database ...
my log:
I/flutter ( 1617): in Paginate to SQLite
E/flutter ( 1617): [ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: DatabaseException(error database_closed)
E/flutter ( 1617): #0 SqfliteDatabaseMixin.checkNotClosed (package:sqflite_common/src/database_mixin.dart:282:7)
E/flutter ( 1617): #1 SqfliteDatabaseExecutorMixin._rawQuery (package:sqflite_common/src/database_mixin.dart:125:8)
E/flutter ( 1617): #2 SqfliteDatabaseExecutorMixin.query (package:sqflite_common/src/database_mixin.dart:110:12)
E/flutter ( 1617): #3 MovieProvider.paginate (package:umdb/bloc/movie_provider.dart:24:38)
E/flutter ( 1617): #4 MovieService.getAllMoviesFromSqlite (package:umdb/services/movie_service.dart:54:23)
E/flutter ( 1617): <asynchronous suspension>
E/flutter ( 1617): #5 MovieService.getSavedFromSQ (package:umdb/services/movie_service.dart:95:26)
E/flutter ( 1617): #6 MovieService.fetchSavedMovies (package:umdb/services/movie_service.dart:105:5)
E/flutter ( 1617): <asynchronous suspension>
E/flutter ( 1617): #7 MovieDetailState.build.<anonymous closure>.<anonymous closure> (package:umdb/ui_widgets/movie_detail.dart:168:42)
E/flutter ( 1617): #8 State.setState (package:flutter/src/widgets/framework.dart:1240:30)
E/flutter ( 1617): #9 MovieDetailState.build.<anonymous closure> (package:umdb/ui_widgets/movie_detail.dart:142:27)
E/flutter ( 1617): #10 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:184:24)
E/flutter ( 1617): #11 TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:524:11)
E/flutter ( 1617): #12 BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:284:5)
E/flutter ( 1617): #13 BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:256:7)
E/flutter ( 1617): #14 GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:158:27)
E/flutter ( 1617): #15 GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:224:20)
E/flutter ( 1617): #16 GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:200:22)
E/flutter ( 1617): #17 GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:158:7)
E/flutter ( 1617): #18 GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:104:7)
E/flutter ( 1617): #19 GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:88:7)
E/flutter ( 1617): #20 _rootRunUnary (dart:async/zone.dart:1206:13)
E/flutter ( 1617): #21 _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 1617): #22 _CustomZone.runUnaryGuarded (dart:async/zone.dart:1005:7)
E/flutter ( 1617): #23 _invoke1 (dart:ui/hooks.dart:267:10)
E/flutter ( 1617): #24 _dispatchPointerDataPacket (dart:ui/hooks.dart:176:5)
please help me to fix it

Answer 1

It is very hard to deal with opening/closing the database. There are indeed many cases where you might access a closed database and even worse, if you open twice the same database, you get the same instance so the first close will close the database.
Personally I recommend keeping the database open.
If you need to handle multiple databases and open/close them for short actions, make sure you have the proper mutex/lock mechanism so that you control how your database is opened/accessed/closed without any other method trying to access the same database at the same time (ok that part is not clear sorry).
Something like that (although I really don't recommend opening/closing each time):
import 'package:synchronized/synchronized.dart';
final static _lock = Lock();
static Future<bool> saveAllMoviesIntoSqlite(List<Movie> movies) async {
return _lock.synchronized(() {
var db = new MovieProvider();
await db.openMovieDB();
await db.insertAll(movies);
await db.closeMovieDB();
return true;
});
}
static Future<Map> getAllMoviesFromSqlite(int page) async {
return _lock.synchronized(() {
var db = new MovieProvider();
await db.openMovieDB();
List<Movie> movies = new List<Movie> ();
movies = await db.paginate(page);
await db.closeMovieDB();
return {
"currentPage": page,
"movies": movies
};
});
}

Answer 2

You need to set null for your database instance when you close your database. Otherwise it will always return the old instance.
Future close() async {
final db = await instance.database;
_database = null;
return db.close();
}

Answer 3

Keeping database without close, and using Singleton pattern is a good choice to solve this problem.
1- Create new file sql_lite_service.dart, this will contains SqlLiteService class with this full code:
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
class SqlLiteService {
String dBName = 'my_db_name';
int dBVersion = 1;
// Singleton pattern
static final SqlLiteService _databaseService = SqlLiteService._internal();
factory SqlLiteService() => _databaseService;
SqlLiteService._internal();
static Database? _database;
Future<Database> get database async {
if (_database != null) return _database!;
_database = await _initDatabase();
return _database!;
}
Future<Database> _initDatabase() async {
// Set the version. This executes the onCreate function and provides a
// path to perform database upgrades and downgrades.
Database db = await _getDB();
return db;
}
Future<Database> _getDB() async{
final path = await _getPath(); // Get a location using getDatabasesPath
return await openDatabase(
path,
onCreate: _onCreate,
version: dBVersion,
onConfigure: (db) async => await db.execute('PRAGMA foreign_keys = ON'),
);
}
// create tables
Future<void> _onCreate(Database db, int version) async {
// Run the CREATE {users} TABLE statement on the database.
await db.execute(
'CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, created_at datetime default current_timestamp, updated_at datetime default current_timestamp)'
);
// todo: Add your code here ...
}
Future<String> _getPath() async {
String databasesPath = await getDatabasesPath();
String path = join(databasesPath, dBName);
return path;
}
}
2- Now you can get Database instance from any other class by:
final Database database = await SqlLiteService().database;
// usage example
await database.rawDelete(
'DELETE FROM users WHERE id = ?',
[1]
);
Using this way will solve database_closed error...