It's been a while I started flutter. And now I am working on the database part. I started with sqflite since it was the ideal one for offline apps but now I can't understand a thing please can somebody help me with this.
import 'package:flutter/widgets.dart';
import 'note.dart';
import 'package:sqflite/sqflite.dart';
import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
class DatabaseHelper {
static DatabaseHelper _databaseHelper = DatabaseHelper();
static Database? _database;
String noteTable = 'note_table';
String colID = 'id';
String colTitle = 'title';
String colDescription = 'description';
String colPriority = 'priority';
String colDate = 'date';
DatabaseHelper._createInstance();
factory DatabaseHelper() {
if (_databaseHelper == null) {
var databaseHelper = DatabaseHelper._createInstance();
_databaseHelper = databaseHelper;
}
return _databaseHelper;
}
//custom getter for the database
Future<Database> get database async {
// ignore: prefer_conditional_assignment
if (_database == null) {
_database = await initializeDatabase();
}
return _database!;
}
Future<Database> initializeDatabase() async {
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'note.db';
var notesDatabase =
await openDatabase(path, version: 1, onCreate: _createDb);
return notesDatabase;
}
void _createDb(Database db, int newVersion) async {
await db.execute(
'CREATE TABLE $noteTable($colID INTEGER PRIMARY KEY AUTOINCREMENT, $colTitle TEXT, $colDescription TEXT, $colPriority INTEGER, $colDate TEXT)');
}
Future<List<Map<String, dynamic>>> getNoteMapList() async {
Database db = await this.database;
var result = await db.query(noteTable, orderBy: '$colPriority ASC');
return result;
}
Future<int> insertData(Note note) async {
Database db = await this.database;
var result = await db.insert(noteTable, note.toMap());
return result;
}
Future<int> updateNote(Note note) async {
Database db = await this.database;
var result = await db
.update(noteTable, note.toMap(), where: '$colID', whereArgs: [note.id]);
return result;
}
Future<int> deleteNote(int id) async {
Database db = await this.database;
var result =
await db.rawDelete('DELETE FROM $noteTable where $colID = $id');
return result;
}
Future<int> getCount() async {
Database db = await this.database;
List<Map<String, dynamic>> x =
await db.rawQuery('SELECT COUNT (*) FROM $noteTable');
int? result = Sqflite.firstIntValue(x);
return result!;
}
Future<List<Note>> getNoteList() async {
var noteMapList = await getNoteMapList();
int count = noteMapList.length;
}
}
This is the whole code. I have watched many videos but can't understand a thing. The problem starts when I the database part starts. And while answering the questions please try to be a little simple.
I need help :(
I'm trying to delete Data from a Sqflite Database.
I can insert and get the data to show, but I cannot delete it if I do a mistake in saving it.
I have my DB:
import 'package:sqflite/sqflite.dart' as sql;
import 'package:path/path.dart' as path;
import 'package:sqflite/sqflite.dart';
//SQFLITE
class DBHelper {
static Future<sql.Database> database() async {
final dbPath = await sql.getDatabasesPath();
//einmal die Datenbank erstellen in einer Variablen
return sql.openDatabase(path.join(dbPath, 'wanderwege.db'),
onCreate: (db, version) {
return db.execute(
'CREATE TABLE user_places(id TEXT PRIMARY KEY, title TEXT, image TEXT, createTime TEXT, place TEXT, description TEXT)');
// 'CREATE TABLE user_places(id TEXT PRIMARY KEY, title TEXT, image TEXT, loc_lat REAL, loc_lng REAL, address TEXT)');
}, version: 1);
}
//Da der Eintrag dauern kann bis es in die Daten gespeichert weerden = Future + async
static Future<void> insert(String table, Map<String, Object> data) async {
final db = await DBHelper.database();
db.insert(table, data, conflictAlgorithm: sql.ConflictAlgorithm.replace);
}
// Delete data from table
// deleteData(table, itemId) async {
// final db = await DBHelper.database();
// return await db.rawDelete("DELETE FROM $table WHERE id = $itemId");
// }
//Methode um Einträge zu holen
static Future<List<Map<String, dynamic>>> getData(String table) async {
final db = await DBHelper.database();
return db.query(table);
}
}
Then I have my Places:
import 'dart:io';
import 'package:flutter/widgets.dart';
import 'package:places/helpers/db_helper.dart';
import 'package:places/models/place.dart';
import 'package:intl/intl.dart';
class GreatPlaces with ChangeNotifier {
//To set Creation Time
static DateTime actualTime = DateTime.now();
String formattedDate = DateFormat('dd-MM-yyyy').format(actualTime);
List<Place> _items = [];
List<Place> get items {
return [..._items];
}
//Information des gesamten places
Place findById(String id) {
return items.firstWhere((place) => place.id == id);
}
Future<void> addPlace(
String pickedTitle,
File pickedImage,
String pickedDate,
String pickedLocation,
String pickedDescription,
//PlaceLocation pickedLocation,
) async {
//final address = await LocationHelper.getPlaceAddress(
// pickedLocation.latitude, pickedLocation.longitude);
// final updatedLocation = PlaceLocation(
// latitude: pickedLocation.latitude,
// longitude: pickedLocation.longitude,
// address: address);
final newPlace = Place(
id: DateTime.now().toString(),
image: pickedImage,
title: pickedTitle,
createTime: pickedDate,
place: pickedLocation,
description: pickedDescription,
);
//location: null);
_items.add(newPlace);
notifyListeners();
//übergabe 'wanderwege' so wie in db_helper definiert , Data ist von typ map
DBHelper.insert('user_places', {
'id': newPlace.id,
'title': newPlace.title,
'image': newPlace.image.path,
'createTime': newPlace.createTime,
'place': newPlace.place,
'description': newPlace.description
// 'loc_lat': newPlace.location.latitude,
// 'loc_lng': newPlace.location.longitude,
// 'address': newPlace.location.address,
});
}
//Die ganzen places aus der DB holen
Future<void> fetchAndSetPlaces() async {
final dataList = await DBHelper.getData('user_places');
_items = dataList
.map((item) => Place(
id: item['id'],
title: item['title'],
image: File(item['image']),
createTime: item['createTime'],
place: item['place'],
description: item['description'],
//location: null // latitude: item['loc_lat'],
// longitude: item['loc_lat'],
// address: item['address']),
))
.toList();
notifyListeners();
}
}
and now on the screen where all the Places listed I want to implement a delete function, but I don't get how it works... tried so much from youtube and the documentation from Sqflite, but I don't get it.
I hope someone can help me.
Greetings :)
I've made this simple helper file (like you have done) for a little app that uses sqflite as backend in local. It's complete: it accesses to the local file system to get grant permissions, it opens the file for write , and you can make also Batch updates:
import 'dart:async';
import 'package:sqflite/sqflite.dart';
class DBClient {
final logger = Log.getLogger('\u{1F5AB} DBClient '); // a little logger utility, you can substitute with the simple 'print(...)' function.
static final String dbFilename = 'my_database.db';
final Permission permission;
Database _database;
bool openingDB = false;
DBClient(this.permission) : assert(permission != null);
Batch batch() {
return _database.batch();
}
Future<void> init() async {
if (_database == null && !openingDB) {
String path;
try {
path = await permission.getAbsoluteFileName(dbFilename);
} on Error {
logger.e('Error: cannot open db');
rethrow;
}
openingDB = true;
logger.d('Opening database on path: $path');
_database = await openDatabase(path, version: 1,
onCreate: (Database db, int version) async {
await db.execute("""
CREATE TABLE IF NOT EXISTS ......
""");
await db.execute("""
CREATE TABLE IF NOT EXISTS ....
""");
....
await db.execute("""
CREATE TABLE IF NOT EXISTS ....
""");
});
}
}
Future<int> insert(String tableName, Map<String, dynamic> json) async =>
_database.insert(tableName, json);
Future<List<Map<String, dynamic>>> query(
String tableName, {
String where,
List<dynamic> whereArgs,
}) async {
return _database.query(
tableName,
where: where,
whereArgs: whereArgs,
);
}
Future<int> update(String tableName, Map<String, dynamic> json,
{String where, List<dynamic> whereArgs}) async {
return _database.update(
tableName,
json,
where: where,
whereArgs: whereArgs,
);
}
Future<int> delete(String tableName,
{String where, List<dynamic> whereArgs}) async {
return _database.delete(
tableName,
where: where,
whereArgs: whereArgs,
);
}
}
You can use in this manner:
deleted = await db.delete(Place.tableName(),
where: "name = ?", whereArgs: [name]);
Hint: in the init() method you can use AsyncMemoizer class, it is better to grant that the method is called only once (at the time I wrote the app I didn't do it....)
Hereafter my (very old) dependencies:
dependencies:
date_utils: ^0.1.0+3
equatable: ^1.1.1
logger: ^0.8.3
permission_handler: ^5.0.0+hotfix.3
quiver: ^2.1.3
sqflite: ^1.3.0
path_provider: ^1.6.5
flutter:
sdk: flutter
String q = "DELETE FROM Test WHERE id= '$id'";
Just use this:
await db.rawDelete('DELETE FROM $table WHERE id = ?',[itemId],);
Just use this function with parameter as id
Future<int> delete(int id) async {
return await db.delete(tableName, where: '$columnId = ?', whereArgs: [id]);}
I am trying to get an async function _read() to run and the function does not pass the line:
Reading reading = await helper.queryReading(rowId); in this function:
_read() async {
DatabaseHelper helper = DatabaseHelper.instance;
int rowId = 1;
//lines above here executes
Reading reading = await helper.queryReading(rowId); //this is the line it stops on
// nothing below here is executed
if (reading == null) {
print('read row $rowId: empty');
} else {
print('read row $rowId: ${reading.reading}');
}
}
It is being called from the following function
class Profile {
Widget getScreen(){
print("Attempting to read db");
_read();
return Scaffold( ...)
Here is my helper class:
import 'dart:ffi';
import 'dart:io';
import 'package:ema/Readings.dart';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
//table structure
final String tableName = 'Readings';
final String databasecolumnId = '_id';
final String databaseReading = 'Reading';
final String databaseDate = 'Time';
class DatabaseHelper {
//This is the name of the database file on disk
static final _databaseName = "readings.db";
//handles versioning for databases
static final _databaseVersion = 1;
//makes a singleton classs
DatabaseHelper._privateConstructor();
static final DatabaseHelper instance = DatabaseHelper._privateConstructor();
//allows only one item to access the database
static Database _database;
Future<Database> get database async {
_database = await _initDatabase();
return database;
}
//this opens and creates the database
_initDatabase() async {
// The path_provider plugin gets the right directory for Android or iOS.
Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, _databaseName);
// Open the database. Can also add an onUpdate callback parameter.
return await openDatabase(path,
version: _databaseVersion,
onCreate: _onCreate);
}
//Creates the database
Future _onCreate(Database db, int version) async {
await db.execute(
'''
CREATE TABLE $tableName (
$databasecolumnId INTEGER PRIMARY KEY,
$databaseReading REAL NOT NULL,
$databaseDate INTERGER NOT NULL
)
'''
);
}
Future<int> insertReading(Reading reading) async {
Database db = await database;
int id = await db.insert(tableName, reading.toMap());
return id;
}
//gets reading
Future<Reading> queryReading(int id) async {
print("queryReading"); //gets here
Database db = await database;
print("Getting Db"); // not actually getting here
List<Map> maps = await db.query(tableName,
columns: [databasecolumnId, databaseReading, databaseDate],
where: '$databasecolumnId = ?',
whereArgs: [id]);
if (maps.length > 0) {
return Reading.fromMap(maps.first);
}
print('maps length : ${maps.length}');
return null;
}
}
Here is my Readings class:
class Reading {
int id;
double reading;
DateTime date;
//constructor
Reading({this.id, this.reading, this.date});
Map<String, dynamic> toMap() {
var map = <String, dynamic>{
databaseReading: reading,
databaseDate: date.millisecondsSinceEpoch,
};
if (id != null) {
map[databasecolumnId] = id;
}
return map;
}
//extracts a node object from the map obect
Reading.fromMap(Map<String, dynamic> map) {
id = map[databasecolumnId];
reading = map[databaseReading];
date = new DateTime.fromMillisecondsSinceEpoch(map [databaseDate]);
}
}
Turns out there was a deadlock in getting the database. By putting a lock on it it worked.
Here is the code to resolve it:
///declreation of the database
Database _database;
///Gets the database ensuring that there are no locks currently on the database
Future<Database> get database async {
if (_database != null) return _database;
_database = await _initDatabase();
return _database;
}
I want to get the real Id of object how's I create in real time without close page and return back to it
because I use initState() to get data from Database and if I tried to get Id without do that it will return 1 ;
any one know why this happened and who to fix it ?
this my Function:
item(String name,String desc,int rate) async{
int savedItem = await db.saveMovie(Movie(name, desc,rate.toString()));
Movie addedItem = await db.getMovie(savedItem);
setState(() {
movies.add(addedItem);
});
print("Item id :${addedItem.id} Saved item : ${savedItem}");
}
and this my database helper code :
import 'dart:async';
import 'package:sqflite/sqflite.dart';
import 'dart:io';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:mblists/models/movies.dart';
class DatabaseHelper {
final String moviesTable = "moviesTable";
final String idColumn = "id";
final String nameColumn = "name";
final String descriptionColumn = "description";
final String rateColumn = "rate";
static final DatabaseHelper _instance = DatabaseHelper.internal();
factory DatabaseHelper() => _instance;
static Database _db;
Future<Database> get db async{
if(_db != null){
return _db;
}
_db = await initDb();
return _db;
}
DatabaseHelper.internal();
initDb() async{
Directory fileDirectory = await getApplicationDocumentsDirectory();
String path = join(fileDirectory.path,"maindatabase.db");
var maindb = await openDatabase(path,version: 1,onCreate: _onCreate);
return maindb;
}
void _onCreate(Database db,int newVersion) async{
await db.execute(
"CREATE TABLE $moviesTable($idColumn INTEGER PRIMARY KEY, $nameColumn TEXT, $descriptionColumn TEXT, $rateColumn TEXT)");
}
Future<int> saveMovie(Movie movie) async{
var dbClient = await db;
int res = await dbClient.insert("$moviesTable", movie.toMap());
return res;
}
Future<List> getAllMovies() async{
var dbClient = await db;
var result = await dbClient.rawQuery("SELECT * FROM $moviesTable");
return result;
}
Future<Movie> getMovie(int id) async{
var dbClient = await db;
var result = await dbClient.rawQuery("SELECT * FROM $moviesTable WHERE $id = $id");
if(result.length == 0) {
return null;
}
return Movie.formMap(result.first);
}
Future<int> getCount() async {
var dbCllient = await db;
return Sqflite.firstIntValue(
await dbCllient.rawQuery("SELECT COUNT(*) FROM $moviesTable")
);
}
Future<int> deleteMovie(int id) async {
var dbClient = await db;
return await dbClient.delete(moviesTable,where: "$idColumn = ?",whereArgs: [ id]);
}
Future<int> deleteMovies() async {
var dbClient = await db;
return await dbClient.delete(moviesTable);
}
Future<int> updateMovie(Movie movie) async {
var dbClient = await db;
return await dbClient.update(moviesTable,movie.toMap(),
where: "$idColumn = ?" , whereArgs: [movie.id]
);
}
Future colse() async{
var dbClient = await db;
return await dbClient.close();
}
}
Insert method returns correct new id, but you have a typo in getMovie:
var result = await dbClient.rawQuery("SELECT * FROM $moviesTable WHERE $id = $id");
WHERE condition should contain column name, but your has id = id condition (which is always true) and then it takes the first element (always the same one). Fix it by passing id column's name:
var result = await dbClient.rawQuery("SELECT * FROM $moviesTable WHERE $idColumn = $id");
And it works:
I/flutter ( 5996): Item id :13 Saved item : {id: 13, name: test, description: desc, rate: 1}
I/flutter ( 5996): Item id :14 Saved item : {id: 14, name: test, description: desc, rate: 1}
I/flutter ( 5996): Item id :15 Saved item : {id: 15, name: test, description: desc, rate: 1}
I am working on SqFlite programme but it shows ArgumentError Exception.
My code is not working it showing I can not insert data into database.
Please some one help me with this.SQFlite Operation like CRUD is not performing.
Exception like ArgumentError Exception like occurring some default dart file with Exception Showing.
Exception throw ArgumentError("nullColumnHack required when inserting no data");
import 'dart:async';
import 'dart:io';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqlite_app/models/note.dart';
class DatabaseHelper {
static DatabaseHelper _databaseHelper;
static Database _database;
String noteTable = 'note_table';
String colId = 'id';
String colTitle = 'title';
String colDescription = 'description';
String colPriority = 'priority';
String colDate = 'date';
DatabaseHelper._createInstance();
factory DatabaseHelper(){
if (_databaseHelper == null) {
_databaseHelper = DatabaseHelper._createInstance();
}
return _databaseHelper;
}
Future<Database> get databse async {
if (_database == null) {
_database = await initalizeDatabase();
}
return _database;
}
Future<Database> initalizeDatabase() async {
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'note.db';
var noteDatabase = await openDatabase(
path, version: 1, onCreate: _createDb);
return noteDatabase;
}
void _createDb(Database db, int newVersion) async {
await db.execute(
'CREATE TABLE $noteTable ($colId INTEGER PRIMARY KEY AUTOINCREMENT,$colTitle TEXT,'
'$colDescription TEXT,$colPriority INTEGER,$colDate TEXT)');
}
Future<List<Map<String, dynamic>>> getNoteMapList() async {
Database db = await this.databse;
//var result=await db.rawQuery('SELECT * FROM $noteTable order by $colPriority ASC');
var result = await db.query(noteTable, orderBy: '$colPriority ASC');
return result;
}
Future<int> insertNote(Note note) async {
Database db = await this.databse;
var result = await db.insert(noteTable, note.toMap());
return result;
}
Future<int> updateNote(Note note) async {
var db = await this.databse;
var result = await db.update(
noteTable, note.toMap(), where: '$colId=?', whereArgs: [note.id]);
return result;
}
Future<int> deleteNote(int id) async {
var db = await this.databse;
int result = await db.rawDelete('DELETE FROM $noteTable WHERE $colId=$id');
return result;
}
Future<int> getCount() async {
Database db = await this.databse;
List<Map<String, dynamic>> x = await db.rawQuery(
"SELECT COUNT (*) from $noteTable");
int result = Sqflite.firstIntValue(x);
return result;
}
Future<List<Note>> getNoteList() async {
var noteMapList = await getNoteMapList();
int count = noteMapList.length;
List<Note> noteList = List<Note>();
for (int i = 0; i < count; i++) {
noteList.add(Note.fromMapObject(noteMapList[i]));
}
return noteList;
}
}
Just pass one more argument in db.insert(i.e. nullColumnHack) with value equal to the Auto Incrementing ID Integer...it will work...Do this for all other operations...
Future<int> insertNote(Note note) async {
Database db = await this.databse;
var result = await db.insert(noteTable, note.toMap(),nullColumnHack: colId);
return result;
}