Flutter 中常用的数据库框架主要包括以下几种：
- SQFlite
- Moor (Drift)
- Hive
- ObjectBox
下面将详细介绍这几种数据库框架，并提供示例代码。
1. SQFlite
SQFlite 是 Flutter 中最常用的 SQLite 数据库插件。它提供了对 SQLite 数据库的完整支持，包括执行 SQL 查询、插入、更新和删除操作。
安装
在 pubspec.yaml 文件中添加依赖：
dependencies:
sqflite: ^2.0.0+4
path: ^1.8.0
示例代码
import 'package:flutter/material.dart';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
final database = openDatabase(
join(await getDatabasesPath(), 'example.db'),
onCreate: (db, version) {
return db.execute(
'CREATE TABLE dogs(id INTEGER PRIMARY KEY, name TEXT, age INTEGER)',
);
},
version: 1,
);
Future<void> insertDog(Dog dog) async {
final db = await database;
await db.insert(
'dogs',
dog.toMap(),
conflictAlgorithm: ConflictAlgorithm.replace,
);
}
Future<List<Dog>> dogs() async {
final db = await database;
final List<Map<String, dynamic>> maps = await db.query('dogs');
return List.generate(maps.length, (i) {
return Dog(
id: maps[i]['id'],
name: maps[i]['name'],
age: maps[i]['age'],
);
});
}
runApp(MyApp());
}
class Dog {
final int id;
final String name;
final int age;
Dog({required this.id, required this.name, required this.age});
Map<String, dynamic> toMap() {
return {'id': id, 'name': name, 'age': age};
}
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text('SQFlite Example')),
body: Center(child: Text('SQFlite Example')),
),
);
}
}
2. Moor (Drift)
Moor (Drift) 是一个更高级的 SQLite 包装库，提供了 Dart 原生支持，类型安全，并且使用简单。
安装
在 pubspec.yaml 文件中添加依赖：
dependencies:
drift: ^2.0.0
drift_sqflite: ^2.0.0
path_provider: ^2.0.7
path: ^1.8.0
dev_dependencies:
drift_dev: ^2.0.0
build_runner: ^2.0.6
示例代码
import 'package:drift/drift.dart';
import 'package:drift/native.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart' as p;
import 'dart:io';
part 'main.g.dart';
LazyDatabase _openConnection() {
return LazyDatabase(() async {
final dbFolder = await getApplicationDocumentsDirectory();
final file = File(p.join(dbFolder.path, 'db.sqlite'));
return NativeDatabase(file);
});
}
@DriftDatabase(tables: [Todos])
class MyDatabase extends _$MyDatabase {
MyDatabase() : super(_openConnection());
@override
int get schemaVersion => 1;
Future<List<Todo>> getAllTodos() => select(todos).get();
Future insertTodo<Todo>(Insertable<Todo> todo) => into(todos).insert(todo);
}
class Todos extends Table {
IntColumn get id => integer().autoIncrement()();
TextColumn get title => text().withLength(min: 1, max: 50)();
BoolColumn get completed => boolean().withDefault(Constant(false))();
}
void main() {
final db = MyDatabase();
runApp(MyApp(db: db));
}
class MyApp extends StatelessWidget {
final MyDatabase db;
MyApp({required this.db});
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text('Drift Example')),
body: FutureBuilder<List<Todo>>(
future: db.getAllTodos(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return CircularProgressIndicator();
} else if (snapshot.hasError) {
return Text('Error: ${snapshot.error}');
} else {
final todos = snapshot.data ?? [];
return ListView.builder(
itemCount: todos.length,
itemBuilder: (context, index) {
final todo = todos[index];
return ListTile(
title: Text(todo.title),
trailing: Checkbox(
value: todo.completed,
onChanged: (newValue) {},
),
);
},
);
}
},
),
floatingActionButton: FloatingActionButton(
onPressed: () {
db.insertTodo(TodosCompanion(
title: Value('New Todo'),
completed: Value(false),
));
},
child: Icon(Icons.add),
),
),
);
}
}
3. Hive
Hive 是一个轻量级和快速的键值对数据库，特别适用于需要存储大量数据的应用。
安装
在 pubspec.yaml 文件中添加依赖：
dependencies:
hive: ^2.0.0
hive_flutter: ^1.1.0
示例代码
import 'package:flutter/material.dart';
import 'package:hive/hive.dart';
import 'package:hive_flutter/hive_flutter.dart';
void main() async {
await Hive.initFlutter();
await Hive.openBox('myBox');
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text('Hive Example')),
body: Center(
child: ValueListenableBuilder(
valueListenable: Hive.box('myBox').listenable(),
builder: (context, Box box, widget) {
return Text('Stored Value: ${box.get('key')}');
},
),
),
floatingActionButton: FloatingActionButton(
onPressed: () {
var box = Hive.box('myBox');
box.put('key', 'Hello Hive');
},
child: Icon(Icons.add),
),
),
);
}
}
4. ObjectBox
ObjectBox 是一个高性能的嵌入式数据库，支持 NoSQL 数据模型，非常适合移动设备。
安装
在 pubspec.yaml 文件中添加依赖：
dependencies:
objectbox: ^2.0.0
objectbox_flutter_libs: ^1.1.0
示例代码
import 'package:flutter/material.dart';
import 'package:objectbox/objectbox.dart';
import 'objectbox.g.dart'; // 需要使用 `objectbox` 生成
@Entity()
class Note {
int id;
String text;
Note({
this.id = 0,
required this.text,
});
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
late final Store _store;
late final Box<Note> _noteBox;
MyApp() {
_store = Store(getObjectBoxModel());
_noteBox = _store.box<Note>();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text('ObjectBox Example')),
body: FutureBuilder<List<Note>>(
future: Future.value(_noteBox.getAll()),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return CircularProgressIndicator();
} else if (snapshot.hasError) {
return Text('Error: ${snapshot.error}');
} else {
final notes = snapshot.data ?? [];
return ListView.builder(
itemCount: notes.length,
itemBuilder: (context, index) {
final note = notes[index];
return ListTile(
title: Text(note.text),
);
},
);
}
},
),
floatingActionButton: FloatingActionButton(
onPressed: () {
final note = Note(
text: 'New Note',
);
_noteBox.put(note);
},
child: Icon(Icons.add),
),
),
);
}
}
这些示例代码展示了如何在 Flutter 中使用各种数据库框架进行数据存储和管理。每个框架都有其优点，选择合适的框架可以根据具体项目的需求来决定。
