Flutter SQLite使用
2024-06-17 06:17:08
文章目录
- Flutter SQLite使用
- 概述
- 添加依赖
- 使用SQLite
- 使用单例类
- 初始化
- 增删改查操作
- 完整代码如下
- 数据库管理类
- 定义实体类
- 首页代码
- 添加数据页面
Flutter SQLite使用
概述
保存数据到本地是应用程序非常重要的功能之一，比如如下场景：一个新闻类或者博客类的应用程序，打开后进入首页，如果本地没有保存数据，则需要通过网络获取数据，在返回数据之前，用户看到的是空白页面，而如果本地保存了部分新闻，则显示这部分数据，等待最新的数据返回时在刷新即可，对用户体验来说，明显第二种体验更佳。
SQLite 是目前最受欢迎的本地存储框架之一。
文件保存路径：/data/data/<package_name>/app_flutter目录下
添加依赖
dependencies:path_provider: ^2.0.11sqflite: ^2.0.2+1
使用SQLite
使用单例类
class DBManager {static final DBManager _instance = DBManager._();factory DBManager() {return _instance;}DBManager._();
}
初始化
class DBManager {/// 数据库名final String _dbName = "dbName";/// 数据库版本final int _version = 1;static final DBManager _instance = DBManager._();factory DBManager() {return _instance;}DBManager._();static Database? _db;Future<Database> get db async {// if (_db != null) {// return _db;// }// _db = await _initDB();// return _db;return _db ??= await _initDB();}/// 初始化数据库Future<Database> _initDB() async {Directory directory = await getApplicationDocumentsDirectory();String path = join(directory.path, _dbName);return await openDatabase(path,version: _version,onCreate: _onCreate,onUpgrade: _onUpgrade,);}/// 创建表Future _onCreate(Database db, int version) async {const String sql = """CREATE TABLE Student(id INTEGER primary key AUTOINCREMENT,name TEXT,age INTEGER,sex INTEGER)""";return await db.execute(sql);}/// 更新表Future _onUpgrade(Database db, int oldVersion, int newVersion) async {}
}
增删改查操作
/// 保存数据
Future saveData(Student student) async {Database database = await db;return await database.insert("Student", student.toJson());
}/// 使用SQL保存数据
Future saveDataBySQL(Student student) async {const String sql = """INSERT INTO Student(name,age,sex) values(?,?,?)""";Database database = await db;return await database.rawInsert(sql, [student.name, student.age, student.sex]);
}/// 查询全部数据
Future<List<Student>?> findAll() async {Database? database = await db;List<Map<String, Object?>> result = await database.query("Student");if (result.isNotEmpty) {return result.map((e) => Student.fromJson(e)).toList();} else {return [];}
}///条件查询
Future<List<Student>?> find(int sex) async {Database database = await db;List<Map<String, Object?>> result =await database.query("Student", where: "sex=?", whereArgs: [sex]);if (result.isNotEmpty) {return result.map((e) => Student.fromJson(e)).toList();} else {return [];}
}/// 修改
Future<int> update(Student student) async {Database database = await db;student.age = 99;int count =await database.update("Student", student.toJson(), where: "id=?", whereArgs: [student.id]);return count;
}/// 删除
Future<int> delete(int id) async {Database database = await db;int count = await database.delete("Student", where: "id=?", whereArgs: [id]);return count;
}/// 删除全部
Future<int> deleteAll() async {Database database = await db;int count = await database.delete("Student");return count;
}
完整代码如下
数据库管理类
class DBManager {/// 数据库名final String _dbName = "dbName";/// 数据库版本final int _version = 1;static final DBManager _instance = DBManager._();factory DBManager() {return _instance;}DBManager._();static Database? _db;Future<Database> get db async {// if (_db != null) {// return _db;// }// _db = await _initDB();// return _db;return _db ??= await _initDB();}/// 初始化数据库Future<Database> _initDB() async {Directory directory = await getApplicationDocumentsDirectory();String path = join(directory.path, _dbName);return await openDatabase(path,version: _version,onCreate: _onCreate,onUpgrade: _onUpgrade,);}/// 创建表Future _onCreate(Database db, int version) async {const String sql = """CREATE TABLE Student(id INTEGER primary key AUTOINCREMENT,name TEXT,age INTEGER,sex INTEGER)""";return await db.execute(sql);}/// 更新表Future _onUpgrade(Database db, int oldVersion, int newVersion) async {}/// 保存数据Future saveData(Student student) async {Database database = await db;return await database.insert("Student", student.toJson());}/// 使用SQL保存数据Future saveDataBySQL(Student student) async {const String sql = """INSERT INTO Student(name,age,sex) values(?,?,?)""";Database database = await db;return await database.rawInsert(sql, [student.name, student.age, student.sex]);}/// 查询全部数据Future<List<Student>?> findAll() async {Database? database = await db;List<Map<String, Object?>> result = await database.query("Student");if (result.isNotEmpty) {return result.map((e) => Student.fromJson(e)).toList();} else {return [];}}///条件查询Future<List<Student>?> find(int sex) async {Database database = await db;List<Map<String, Object?>> result =await database.query("Student", where: "sex=?", whereArgs: [sex]);if (result.isNotEmpty) {return result.map((e) => Student.fromJson(e)).toList();} else {return [];}}/// 修改Future<int> update(Student student) async {Database database = await db;student.age = 99;int count =await database.update("Student", student.toJson(), where: "id=?", whereArgs: [student.id]);return count;}/// 删除Future<int> delete(int id) async {Database database = await db;int count = await database.delete("Student", where: "id=?", whereArgs: [id]);return count;}/// 删除全部Future<int> deleteAll() async {Database database = await db;int count = await database.delete("Student");return count;}
}
定义实体类
Student studentFromJson(String str) => Student.fromJson(json.decode(str));String studentToJson(Student data) => json.encode(data.toJson());class Student {Student({this.id,this.name,this.age,this.sex,});Student.fromJson(dynamic json) {id = json['id'];name = json['name'];age = json['age'];sex = json['sex'];}int? id;String? name;int? age;int? sex;Map<String, dynamic> toJson() {final map = <String, dynamic>{};map['id'] = id;map['name'] = name;map['age'] = age;map['sex'] = sex;return map;}
}
首页代码
class SqlitePage extends StatefulWidget {const SqlitePage({Key? key}) : super(key: key);@overrideState<StatefulWidget> createState() {return _SqlitePageState();}
}class _SqlitePageState extends State<SqlitePage> {List<Student>? _studentList;loadAllData() async {_studentList = await DBManager().findAll();setState(() {});}loadData() async {_studentList = await DBManager().find(1);setState(() {});}updateData(Student student) async {var count = await DBManager().update(student);if (count > 0) {showSnackBar(context, "修改成功");} else {showSnackBar(context, "修改失败");}}deleteData(int id) async {var count = await DBManager().delete(id);if (count > 0) {showSnackBar(context, "删除成功");} else {showSnackBar(context, "删除失败");}}deleteAllData() async {var count = await DBManager().deleteAll();if (count > 0) {showSnackBar(context, "删除成功");} else {showSnackBar(context, "删除失败");}}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(title: const Text("SQLite"),actions: [IconButton(icon: const Icon(Icons.add),onPressed: () {Navigator.push(context, MaterialPageRoute(builder: (context) {return const AddStudentPage();}));},)],),body: SingleChildScrollView(child: Center(child: Column(children: [ElevatedButton(onPressed: () {loadAllData();},child: const Text("查询所有数据"),),ElevatedButton(onPressed: () {loadData();},child: const Text("条件查询"),),ElevatedButton(onPressed: () {deleteAllData();},child: const Text("删除全部"),),Padding(padding: const EdgeInsets.all(10),child: _buildTable(),),],),),),);}_buildTable() {return Table(border: TableBorder.all(),defaultVerticalAlignment: TableCellVerticalAlignment.middle,children: [const TableRow(children: [TableCell(child: Text("id")),TableCell(child: Text("姓名")),TableCell(child: Text("年龄")),TableCell(child: Text("性别")),TableCell(child: Text("修改")),TableCell(child: Text("删除")),]),...?_studentList?.map((e) => TableRow(children: [TableCell(child: Text("${e.id}")),TableCell(child: Text("${e.name}")),TableCell(child: Text("${e.age}")),TableCell(child: Text("${e.sex}")),TableCell(child: TextButton(onPressed: () {updateData(e);},child: const Text("修改"),),),TableCell(child: TextButton(onPressed: () {deleteData(e.id!);},child: const Text("删除"),),),])).toList(),],);}
}
添加数据页面
class AddStudentPage extends StatefulWidget {const AddStudentPage({Key? key}) : super(key: key);@overrideState<StatefulWidget> createState() {return _AddStudentPageState();}
}class _AddStudentPageState extends State<AddStudentPage> {int _sexValue = 0;late TextEditingController _nameController;late TextEditingController _ageController;@overridevoid initState() {_nameController = TextEditingController();_ageController = TextEditingController();super.initState();}@overridevoid dispose() {_nameController.dispose();_ageController.dispose();super.dispose();}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(title: const Text("增加学生"),),body: Padding(padding: const EdgeInsets.all(8.0),child: Column(children: [TextField(controller: _nameController,decoration: const InputDecoration(labelText: "姓名："),),TextField(controller: _ageController,decoration: const InputDecoration(labelText: "年龄："),inputFormatters: [FilteringTextInputFormatter.digitsOnly,],),Row(children: [Expanded(child: RadioListTile<int>(title: const Text("女"),value: 0,groupValue: _sexValue,onChanged: (value) {setState(() {_sexValue = value!;});},),),Expanded(child: RadioListTile<int>(title: const Text("男"),value: 1,groupValue: _sexValue,onChanged: (value) {setState(() {_sexValue = value!;});},),),],),Builder(builder: (BuildContext context) {return Column(children: [ElevatedButton(onPressed: () async {var student = Student(name: _nameController.text.toString(),age: int.parse(_ageController.text.toString()),sex: _sexValue,);int result = await DBManager().saveData(student);if (result > 0) {showSnackBar(context, '保存数据成功，result:$result');} else {showSnackBar(context, '保存数据失败，result:$result');}},child: const Text("保存数据"),),ElevatedButton(onPressed: () async {var student = Student(name: _nameController.text.toString(),age: int.parse(_ageController.text.toString()),sex: _sexValue,);int result = await DBManager().saveDataBySQL(student);if (result > 0) {showSnackBar(context, '保存数据成功，result:$result');} else {showSnackBar(context, '保存数据失败，result:$result');}},child: const Text("使用SQL保存数据"),),],);}),],),),);}
}
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