Flutter开发笔记 —— sqflite插件数据库应用

前言

今天在观阅掘金大佬文章的时候，了解到了该 sqflite 插件，结合官网教程和自己实践，由此总结出该文，希望对大家的学习有帮助！

插件详情

Flutter的 SQLite 插件。支持 iOS、Android 和 MacOS。

• 支持事务和batch模式
• 打开时自动进行版本管理
• 插入/查询/更新/删除查询的助手
• iOS 和 Android 上的数据库操作在后台线程中执行

插件地址: https://pub.dev/packages/sqflite

本文使用插件版本为最新版本：2.3.0

基础介绍

数据表创建

• openDatabase() 连接数据库
• deleteDatabase() 删除数据库

openDataBase方法 可选参为db文件地址、版本号、相关回调

案例速览

late Database db;
final database = "book.db";
final table = "book";

/*
 * @author Marinda
 * @date 2023/12/13 15:53
 * @description 连接数据库
 */
connection() async{
  //获取
  var databasePath = await getDatabasesPath();
  String path = p.join(databasePath,database);
  //删除数据库
  await deleteDatabase(path);
  print('当前地址：${path}');
  if(File(path).existsSync()){
    db = await openDatabase(path);
  }else{
    db = await openDatabase(path,version: 1,onCreate: (database,version) async{
      database.execute("CREATE TABLE `${table}` (id integer primary key autoincrement,name text not null,price REAL ,author TEXT NOT NULL,description TEXT)");
    });
  }
}

语句介绍

CURD方法介绍

• 使用SQL语句的CURD前缀带raw (例如rawInsert)
• 官方封装好的CURD语句不带raw(例如insert) ->全文使用该方法

语法速览

//前者
Future<int> rawInsert(String sql, [List<Object?>? arguments]);
//后者
Future<int> insert(String table, Map<String, Object?> values,
    {String? nullColumnHack, ConflictAlgorithm? conflictAlgorithm});

接下来看几个简单的CURD快速了解写法

insert(插入)

Future<int> insert() async{
  Map<String,dynamic> args = {
      "id": 1,
      "name": "张飞",
      "description": "猛将"
  };
  //返回id table为表名
  return await db.insert(table,args);
}

delete(删除)

Future<int> delete(int id) async{
  return await db.delete(table,where: "id = ?",whereArgs: [id]);
}

update(修改)

Future<int> update() async{
  Map<String,dynamic> args = {
      "id": 1,
      "name": "吕布",
      "description": "天下无双"
  };
  return await db.update(table, args,where: "id = ?",whereArgs: [args["id"]]);
}

select(查询)

/*
 * @author Marinda
 * @date 2023/12/13 16:11
 * @description 通过id查询
 */
Future<Map<String,dynamic>?> selectById(int id) async{
  var list = await db.query(table,where: "id = ?",whereArgs: [id]);
  if(list.isNotEmpty){
    return list.first;
  }
  return null;
}

现在我们对sqflite插件的基础使用有一个初步的了解了，接下来围绕一个书本表案例做实战

实战应用

• 定义Book书表作为实体类
• 定义DBBookProvider类处理数据库表

book.dart

/**
 * @author Marinda
 * @date 2023/12/13 15:42
 * @description 书籍信息
 */
class Book {
  int? _id;
  String? _name;
  double? _price;
  String? _author;
  String? _description;

  Book(
      {int? id,
        String? name,
        double? price,
        String? author,
        String? description}) {
    if (id != null) {
      this._id = id;
    }
    if (name != null) {
      this._name = name;
    }
    if (price != null) {
      this._price = price;
    }
    if (author != null) {
      this._author = author;
    }
    if (description != null) {
      this._description = description;
    }
  }

  int? get id => _id;
  set id(int? id) => _id = id;
  String? get name => _name;
  set name(String? name) => _name = name;
  double? get price => _price;
  set price(double? price) => _price = price;
  String? get author => _author;
  set author(String? author) => _author = author;
  String? get description => _description;
  set description(String? description) => _description = description;

  Book.fromJson(Map<String, dynamic> json) {
    _id = json['id'];
    _name = json['name'];
    _price = json['price'];
    _author = json['author'];
    _description = json['description'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this._id;
    data['name'] = this._name;
    data['price'] = this._price;
    data['author'] = this._author;
    data['description'] = this._description;
    return data;
  }
}

db_book_provider.dart

/**
 * @author Marinda
 * @date 2023/12/13 15:43
 * @description 书籍数据库适配器
 */

class DBBookProvider{
  late Database db;
  final database = "book.db";
  final table = "book";
  static DBBookProvider? _instance;
  static DBBookProvider instance = getInstance();
  DBBookProvider._();

  factory DBBookProvider(){
    return instance;
  }

  static getInstance(){
    if(_instance == null){
      _instance = DBBookProvider._();
    }
    return _instance ?? DBBookProvider._();
  }

  /*
   * @author Marinda
   * @date 2023/12/13 15:53
   * @description 连接数据库
   */
  connection() async{
    var databasePath = await getDatabasesPath();
    String path = p.join(databasePath,database);
    // await deleteDatabase(path);
    print('当前地址：${path}');
    if(File(path).existsSync()){
      db = await openDatabase(path);
    }else{
      db = await openDatabase(path,version: 1,onCreate: (database,version) async{
        database.execute("CREATE TABLE `${table}` (id integer primary key autoincrement,name text not null,price REAL ,author TEXT NOT NULL,description TEXT)");
      });
    }
  }


  /*
   * @author Marinda
   * @date 2023/12/13 16:01
   * @description 关闭数据库
   */
  close() async{
    await db.close();
  }

  /*
   * @author Marinda
   * @date 2023/12/13 16:02
   * @description 插入
   */
  Future<Book> insert(Book book) async{
    int id = await db.insert(table,book.toJson());
    book.id = id;
    return book;
  }

  /*
   * @author Marinda
   * @date 2023/12/13 16:08
   * @description 删除id
   */
  Future<int> delete(int id) async{
    return await db.delete(table,where: "id = ?",whereArgs: [id]);
  }

  /*
   * @author Marinda
   * @date 2023/12/13 16:11
   * @description 通过id查询
   */
  Future<Book?> selectById(int id) async{
    var list = await db.query(table,where: "id = ?",whereArgs: [id]);
    if(list.isNotEmpty){
      return Book.fromJson(list.first);
    }
    return null;
  }

  /*
   * @author Marinda
   * @date 2023/12/13 16:13
   * @description 获取所有书籍列表
   */
  Future<List<Book>> queryList() async{s
    var result = await db.query(table);
    return result.map((e) => Book.fromJson(e)).toList();
  }

  /*
   * @author Marinda
   * @date 2023/12/13 16:15
   * @description 修改书籍信息
   */
  Future<int> update(Book book) async{
    return await db.update(table, book.toJson(),where: "id = ?",whereArgs: [book.id]);
  }

}

实例化调用

initDatabase() async{
  DBBookProvider dbBookProvider = DBBookProvider.instance;
  //连接
  await dbBookProvider.connection();
  Book book = Book(
    name: "斗破苍穹",
    author: "天蚕土豆",
    price: 88.00,
    description: "一本不错的小说"
  );
  //插入
  Book element = await dbBookProvider.insert(book);
  print('element : ${element.toJson()}');
  //删除
  for(var id in result){
    await dbBookProvider.delete(id);
  }
 
  Book newBook = Book.fromJson(book.toJson());
  newBook.id = 1;
  newBook.author = "天蚕土豆";
   //修改
  await dbBookProvider.update(newBook);
  //查询全部
  var list = await dbBookProvider.queryList();
  print("当前列表: ${list.map((e) => e.toJson()).toList()}");
}

事务&batch

单独拉出来讲讲的原因是我在应用中踩了个坑

事务和batch是什么这个大家如果不了解的话自行百度一下，下文带大家简单看看案例

/*
 * @author Marinda
 * @date 2023/12/13 16:17
 * @description 批量插入全部书籍列表
 */
insertAll(List<Book> bookList) async{
  List resultList = [];
  await db.transaction((txn) async{
    Batch batch = txn.batch();
    for(var book in bookList){
      batch.insert(table,book.toJson());
    }
    //返回全部结果并且不跳过错误！
    resultList = await batch.commit(noResult: false,continueOnError: false);
    print('resultList: ${resultList}');
  });
  await close();
  return resultList;
}

注：在该案例中配合事务 batch.commit方法中如果continueOnError为false时 出现异常则会中止，导致前面插入回推。

注：在该insertAll()方法 或其他涉及事务的方法，都要执行完毕后主动调用close() 断开本次连接。否则会导致 Error Domain=FMDatabase Code=5 “database is locked”

如果已经出现 Error Domain=FMDatabase Code=5 “database is locked” 错误，请删除该数据库文件，重新生成。

结束语

感谢你的观看，希望对大家学习有帮助，有不对的地方欢迎指正！文章来源地址https://www.toymoban.com/news/detail-758094.html

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