我需要帮助：(
我正试图从Sqflite数据库中删除数据。我可以插入并显示数据，但如果我在保存时出错，我不能删除它。
我有我的数据库：
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);
}
}
然后我有我的位置：
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();
}
}
现在，在列出所有位置的屏幕上，我想实现一个删除功能，但我不知道它是如何工作的。。。从youtube和Sqflite的文档中尝试了很多，但我不明白。
我希望有人能帮助我。
问候：(
我为一个使用sqflite作为本地后端的小应用程序制作了这个简单的助手文件(就像您所做的那样(。它是完整的：它访问本地文件系统以获得授予权限，它打开文件进行写入，您还可以进行批量更新：
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: $path');
_database = await openDatabase(path, version: 1,
onCreate: (Database db, int version) async {
await db.execute("""
CREATE TABLE IF NOT EXISTS ......
""");
await db.execute("""
CREATE TABLE IF NOT EXISTS ....
""");
....
await db.execute("""
CREATE TABLE IF NOT EXISTS ....
""");
});
}
}
Future<int> insert(String tableName, Map<String, dynamic> json) async =>
_database.insert(tableName, json);
Future<List<Map<String, dynamic>>> query(
String tableName, {
String where,
List<dynamic> whereArgs,
}) async {
return _database.query(
tableName,
where: where,
whereArgs: whereArgs,
);
}
Future<int> update(String tableName, Map<String, dynamic> json,
{String where, List<dynamic> whereArgs}) async {
return _database.update(
tableName,
json,
where: where,
whereArgs: whereArgs,
);
}
Future<int> delete(String tableName,
{String where, List<dynamic> whereArgs}) async {
return _database.delete(
tableName,
where: where,
whereArgs: whereArgs,
);
}
}
你可以用这种方式：
deleted = await db.delete(Place.tableName(),
where: "name = ?", whereArgs: [name]);
提示：在init((方法中，您可以使用AsyncMemoizer类，最好允许该方法只调用一次(在我编写应用程序时，我没有这么做……(
以下是我(非常古老的(依赖项：
dependencies:
date_utils: ^0.1.0+3
equatable: ^1.1.1
logger: ^0.8.3
permission_handler: ^5.0.0+hotfix.3
quiver: ^2.1.3
sqflite: ^1.3.0
path_provider: ^1.6.5
flutter:
sdk: flutter
String q = "DELETE FROM Test WHERE id= '$id'";
只需使用此：
await db.rawDelete('DELETE FROM $table WHERE id = ?',[itemId],);
只需将此函数与参数一起用作id
Future<int> delete(int id) async {
return await db.delete(tableName, where: '$columnId = ?', whereArgs: [id]);}