flutter: Warning database has been locked for 0:00:10.000000. Make sure you always use the transaction object - flutter-web

Question

import 'dart:io';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
import '../model/weather.dart';
class DatabaseHelper {
static final _databaseName = "Nithya.db";
static final _databaseVersion = 1;
static final favTable = 'favourites';
static final recentsTable = 'recents';
static final columnCityName = 'cityName';
static final columnCountry = 'country';
static final columnIcon = 'icon';
static final columnTemp = 'temp';
static final columnDescription = 'description';
// make this a singleton class
DatabaseHelper._privateConstructor();
static final DatabaseHelper instance = DatabaseHelper._privateConstructor();
// only have a single app-wide reference to the database
static Database? _database;
Future<Database?> get database async {
if (_database != null) return _database;
// lazily instantiate the db the first time it is accessed
_database = await _initDatabase();
return _database;
}
// this opens the database (and creates it if it doesn't exist)
_initDatabase() async {
Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, _databaseName);
return await openDatabase(path,
version: _databaseVersion, onCreate: _onCreate);
}
// SQL code to create the database table
Future _onCreate(Database db, int version) async {
await db.execute('''
CREATE TABLE $favTable (
$columnCityName TEXT PRIMARY KEY NOT NULL,
$columnCountry TEXT NOT NULL,
$columnIcon TEXT NOT NULL,
$columnTemp TEXT NOT NULL,
$columnDescription TEXT NOT NULL
)
''');
await db.execute('''
CREATE TABLE $recentsTable (
$columnCityName TEXT PRIMARY KEY NOT NULL,
$columnCountry TEXT NOT NULL,
$columnIcon TEXT NOT NULL,
$columnTemp TEXT NOT NULL,
$columnDescription TEXT NOT NULL
)
''');
}
// Helper methods
// Inserts a row in the database where each key in the Map is a column name
// and the value is the column value. The return value is the id of the
// inserted row.
Future<int> insert(Weather weath) async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.insert(favTable, {
'cityName': weath.cityName,
'country': weath.country,
'icon': weath.icon,
'temp': weath.temp,
'description': weath.description
});
});
return result;
}
Future<int> insertRecent(Weather weath) async {
Database db = await instance.database as Database;
var result;
await db.transaction((txn) async {
result = await db.insert(recentsTable, {
'cityName': weath.cityName,
'country': weath.country,
'icon': weath.icon,
'temp': weath.temp,
'description': weath.description
});
});
return result;
}
// All of the rows are returned as a list of maps, where each map is
// a key-value list of columns.
Future<List<Map<String, dynamic>>> queryAllRows() async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.query(favTable);
});
return result;
}
Future<List<Map<String, dynamic>>> queryAllRowsRecent() async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.query(recentsTable);
});
return result;
}
Future<int> delete(cityName) async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.delete(favTable,
where: '$columnCityName = ?', whereArgs: [cityName]);
});
return result;
}
Future<int> deleteRecent(cityName) async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.delete(recentsTable,
where: '$columnCityName = ?', whereArgs: [cityName]);
});
return result;
}
Future<int> deleteAll() async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.delete(favTable);
});
return result;
}
Future<int> deleteAllRecents() async {
var result;
Database db = await instance.database as Database;
await db.transaction((txn) async {
result = await db.delete(recentsTable);
});
return result;
}
}
This is my db helper class. It was working fine before but now it is causing this error
flutter: Warning database has been locked for 0:00:10.000000. Make sure you always use the transaction object for database operations during a transaction.
How to solve this error. I'm new to flutter and sqflite please help.

Answer 1

What the error means is that in you code, instead of having:
await db.transaction((txn) async {
// DEADLOCK, don't use the db object below
result = await db.insert(favTable, {
you should do:
await db.transaction((txn) async {
// CORRECT, use the txn object instead
result = await txn.insert(favTable, {