如何将内部SQLite数据库中的数据与MySQL数据库同步链接，匹配？

编程问答 2022-06-11

问题描述

在MysqL中获取问题时，我想将学生的级别和学生的班级（SQFLite）与学生的级别和学生的班级（MysqL）相匹配。

我有一个外部MysqL数据库（localhost），其中包含一个“问题”表，该表以其级别（容易，中等，困难）和其类（第一类，第二类，第三类）为特征。我有一个内部数据库（SQFLite），其中包含一个“学生”表，其中的级别和类属性包含在外部MysqL数据库中。我只想发布与内部数据库“ SQFLite”中已经添加的学生的级别和班级相对应的问题。

问题：：我以JSON形式发布了所有问题，但与当前添加的学生的级别和班级不符。

要求：我想要在内部数据库“ SQFLite”中添加新学生及其级别和班级时，显示的问题必须与该学生的问题相匹配。

Try.PHP：以json格式获取问题

<?PHP
header("Content-type: application/json; charset=utf-8");
try{
$conn = new PDO('MysqL:host=localhost;dbname=relations;charset=utf8','root','');
$conn ->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $exc){
    echo $exc->getMessage();
    die("Could not connect");
}
?>

<?PHP
$makeQuery ="SELECT * FROM questions ";
$stamement = $conn-> prepare($makeQuery);
$stamement -> execute();
$myarray = array();
while ($resultsFrom = $stamement->fetch()){
    array_push(
        $myarray,array(
        "idques"=>intval($resultsFrom['idques']),"description"=>$resultsFrom['description'] 
        )
    );
}
echo json_encode($myarray);
?>

model.dart：包含学生的模型

class Student {
  int _id;
  String _name;
  String _level;
  String _classes ;
  String _date;

  Student(this._name,this._level,this._classes,this._date);
  Student.withId(this._id,this._name,this._date);

  String get date => _date;
  String get level => _level;
  String get classes => _classes;
  String get name => _name;
  int get id => _id;

  set date(String value) {
    _date = value;
  }
  set level(String value) {
      _level = value;
  }
  set classes(String value) {
    _classes = value;
  }
  set name(String value) {
    if (value.length <= 255) {
      _name = value;
    }
  }

  Map<String,dynamic> toMap() {
    var map = Map<String,dynamic>();
    map["id"] = this._id;
    map["name"] = this._name;
    map["level"] = this._level;
    map["classes"] = this._classes;
    map["date"] = this._date;
    return map;
  }

  Student.getMap(Map<String,dynamic> map){
    this._id = map["id"];
    this._name = map["name"];
    this._level = map["level"];
    this._classes= map["classes"];
    this._date = map["date"];
  }
}

sql_helper.dart：包含内部数据库（SQFLite）

import 'package:sqflite/sqflite.dart';
import 'dart:async';
import 'dart:io';
import 'model.dart';
import 'package:path_provider/path_provider.dart';

class sql_Helper {
  static sql_Helper dbHelper;
  static Database _database;

  sql_Helper._createInstance();
  factory sql_Helper() {
    if (dbHelper == null) {
      dbHelper = sql_Helper._createInstance();
    }
    return dbHelper;
  }

  String tableName = "students_table";
  String _id = "id";
  String __name = "name";
  String __level= "level";
  String __classes = "classes";
  String __date = "date";

  Future<Database> get database async {
    if (_database == null){
      _database = await initializedDatabase();
    }
    return _database;
  }

  Future<Database> initializedDatabase() async {
    Directory directory = await getApplicationDocumentsDirectory();
    String path = directory.path + "students.db";
    var studentDB = await openDatabase(path,version: 1,onCreate: createDatabase);
    return studentDB;
  }

  void createDatabase(Database db,int version) async {
    await db.execute(
        "CREATE TABLE $tableName($_id INTEGER PRIMARY KEY AUTOINCREMENT,$__name TEXT,$__level TEXT,$__classes TEXT,$__date TEXT )");
  }

  Future<List<Map<String,dynamic>>> getStudentMapList() async {
    Database db = await this.database;
    var result = await db.query(tableName,orderBy: "$_id ASC");
    return result;
  }

  Future<int> insertStudent(Student student) async {
    Database db = await this.database;
    var result = await db.insert(tableName,student.toMap());
    return result;
  }

  Future<int> updateStudent(Student student) async{
    Database db = await this.database;
    var result = await db.update(tableName,student.toMap(),where: "$_id = ?",whereArgs: [student.id]);
    return result;
  }

  Future<int> deleteStudent(int id) async {
    var db = await this.database;
    int result = await db.rawDelete("DELETE FROM $tableName WHERE $_id = $id");
    return result;
  }

  Future<int> getCount() async {
    Database db = await this.database;
    List<Map<String,dynamic>> all = await db.rawQuery("SELECT COUNT (*) FROM $tableName");
    int result = Sqflite.firstIntValue(all);
    return result;
  }

  Future<List<Student>> getStudentList() async{
    var studentMapList = await getStudentMapList();
    int count = studentMapList.length;
    List<Student> students = new List<Student>();
    for (int i = 0; i <= count -1; i++){
      students.add(Student.getMap(studentMapList[i]));
    }
    return students;
  }
}

question.dart：包含问题列表

import 'package:Flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

class Questions extends StatefulWidget {
  @override
  _Questionsstate createState() => _Questionsstate();
}

class _Questionsstate extends State<Questions> {
  getmethod()async{
    String theUrl = 'http://10.0.2.2/Try/Try.PHP';
    var res = await http.get(Uri.encodeFull(theUrl),headers:{"Accept":"application/json"});
    var responsBody = json.decode(res.body);
    print(responsBody);
    return responsBody;
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
        title:Text("Questions",style: TextStyle(fontWeight: FontWeight.bold),),backgroundColor: Colors.blue[700],backgroundColor: Colors.blue[99],body:FutureBuilder(
        future: getmethod(),builder: (BuildContext context,AsyncSnapshot snapshot){
          List snap = snapshot.data;
          if(snapshot.connectionState == ConnectionState.waiting){
            return Center(
              child: CircularProgressIndicator(),);
          }
          if(snapshot.hasError){
            return Center(
              child: Text("Error .... "),);
          }
          return ListView.separated(
            separatorBuilder: (context,index) => Divider(
              color: Colors.indigo,itemCount: snap.length,itemBuilder: (context,index){
              return ListTile(
                title: Text(
                    "${snap[index]['description']}",style: TextStyle(fontSize: 18.0)),leading:Icon(Icons.question_answer,color:Colors.green,size: 20,);
            },);
        },);
  }
}

解决方法

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jsonmysqlsqflite