flutter 数据库sqflite的简单使用

sqflite是一款轻量级的关系型数据库，类似SQLite。

使用介绍

1.首先需要在pubspec.yaml 导入库

image.png

2.新建一个model类

class UserModel {
  int? id;
  String name;
  String height;

  UserModel({
    this.id,
    required this.name,
    required this.height,
  });

  factory UserModel.fromMapToModel(Map mapa) => UserModel(
        id: mapa["id"],
        name: mapa["name"],
        height: mapa["height"],
      );

  factory UserModel.fromJson(Map mapa) => UserModel(
        id: mapa["id"],
        name: mapa["name"],
        height: mapa["height"],
      );

  Map toJson() => {
        "id": id,
        "name": name,
        "height": height,
      };
}

3.创建一个DB_Manager

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:sql_demo/database/user_model.dart';

class DBManager {
  Database? myDatabase;
  String tableName = 'mytable';

  static final DBManager db = DBManager._();
  DBManager._();
  Future getCheckDatabase() async {
    if (myDatabase != null) return myDatabase;
    myDatabase = await initDB();
    return myDatabase;
  }

  Future initDB() async {
    Directory directory = await getApplicationDocumentsDirectory();
    String path = join(directory.path, 'MYDB.db');
    print(path);
    return await openDatabase(path, version: 1, onOpen: (db) {},
        onCreate: (Database db, int v) async {
      await db.execute(
          "CREATE TABLE $tableName(id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, height TEXT)");
    });
  }

  Future getDBInfo() async {
    final Database? databaseDB = await getCheckDatabase();
    List res =
        await databaseDB!.query("SELECT * FROM $tableName ORDER BY id DESC");
    return res;
  }

  // 获取所有用户
  Future> getUsers() async {
    List res = [];
    final Database? databaseDB = await getCheckDatabase();
    // print(222);
    List getRes = await databaseDB!.query(tableName, orderBy: 'id DESC');
    // getRes = getRes.reversed.toList();
    // getRes.forEach((element) {
    //   res.add(UserModel.fromMapToModel(element));
    // });
    res = getRes.map((e) => UserModel.fromMapToModel(e)).toList();
    return res;
  }

  customInsetSqlStr(String sqlStr) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!.rawInsert(sqlStr);
    print('执行结果$res');
  }

  // 执行表得插入
  insertToTab() async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!.rawInsert(
        "INSERT INTO $tableName(name,height) VALUES('No Pain, No Gain','J. L. D. Barnett')");
    print('执行结果$res');
  }

  insertUser(UserModel user) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!.insert(tableName, user.toJson());
    //     {
    //   "name":user.name,
    //   "height":user.height,
    // }
    //(res!=null) ? inserted=true: inserted=false;
    print('执行结果$res');
  }

  // 更新表操作
  Future updataTableRaw(UserModel user) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!.rawUpdate(
        "UPDATE $tableName SET name = ${user.name}, author = ${user.height}  WHERE id = ${user.id}");
    return res;
  }

  // 更新用户
  updataUser(UserModel user) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!
        .update(tableName, user.toJson(), where: "id = ${user.id}");
    print('执行结果$res');
  }

  Future deleteTableRaw(int userId) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!
        .rawDelete("DELETE FROM $tableName WHERE id = $userId");
    return res;
  }

  deletaUser(int userId) async {
    final Database? databaseDB = await getCheckDatabase();
    int res = await databaseDB!.delete(tableName, where: "id = $userId");
    print('执行结果$res');
  }
}

4.开始使用

  DBManager.db.getUsers().then((value) {
      users = value;
      setState(() {});
    });
 DBManager.db.insertToTab();
          setState(() {
            getUserList();
          });