How to link the data from the internal SQFLite db with that Mysql (localhost)? Recovered data must be based on data entered into the internal db

[Mohamed-yanis]

I have an external database (localhost) that contains a "questions" table characterized by their level (Easy, Medium, Hard) and class(1st class, 2nd class, 3rd class).
I have an internal database that contains a "student" table with level and class attributes that contain in the external database.
I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".
I posted all the questions in the JSON form but did not match the level and class of the student,
But I want when I add a new student with their level and class in the internal database, the questions that are displayed must be matched to that of the student.

model.dart: contains the student's model

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._level, this._classes ,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: contains the internal database

import 'package:flutter/material.dart';
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;
  }

} 

main.dart

import 'package:flutter/material.dart';
import 'package:relationtables/sql_helper.dart';
import 'package:sqflite/sqflite.dart';
import 'package:http/http.dart' as http;
import 'package:intl/intl.dart';
import 'dart:convert';
import 'model.dart';
import 'dart:async';

void main() {
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      title: "Students List",
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
          primarySwatch: Colors.cyan
      ),
      home: StudentsList(),
    );
  }
}

class StudentsList extends StatefulWidget{
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return StudentsState();
  }
}
class StudentsState extends State<StudentsList> {
  SQL_Helper helper = new SQL_Helper();
  List<Student> studentsList;
  int count = 0;
  @override
  Widget build(BuildContext context) {
    if (studentsList == null) {
      studentsList = new List<Student>();
      updateListView();
    }
    // TODO: implement build
    return Scaffold(
        appBar: AppBar(
          title: Text("Students"),
        ),
        body: getStudentsList(),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            navigateToStudent(Student('','','', ''), "Add New Student");
          },
          tooltip: 'Add Student',
          child: Icon(Icons.add),
        )
    );
  }
  ListView getStudentsList() {
    return ListView.builder(
        itemCount: count,
        itemBuilder: (BuildContext context, int position) {
          return Card(
            color: Colors.white,
            elevation: 2.0,
            child: ListTile(
              leading: Icon(Icons.person_pin),
              title: Text(this.studentsList[position].name),
              subtitle: Text(this.studentsList[position].level+ " | " + this.studentsList[position].classes+'  '+this.studentsList[position].date),
              trailing:
              GestureDetector(
                child: Icon(Icons.delete, color: Colors.grey,),
                onTap: () {
                  _delete(context, this.studentsList[position]);
                },
              )
              ,
              onTap: () {
                Navigator.push(
                    context, MaterialPageRoute(builder: (context) {
                  return Menu();
                }));
              },
            ),
          );
        });
  }
  void _delete(BuildContext context, Student student) async {
    int ressult = await helper.deleteStudent(student.id);
    if (ressult != 0) {
      _showSenckBar(context, "Student has been deleted");
      updateListView();
    }
  }
  void _showSenckBar(BuildContext context, String msg) {
    final snackBar = SnackBar(content: Text(msg),);
    Scaffold.of(context).showSnackBar(snackBar);
  }
  void updateListView() {
    final Future<Database> db = helper.initializedDatabase();
    db.then((database) {
      Future<List<Student>> students = helper.getStudentList();
      students.then((theList) {
        setState(() {
          this.studentsList = theList;
          this.count = theList.length;
        });
      });
    });
  }
  void navigateToStudent(Student student, String appTitle) async {
    bool result = await Navigator.push(
        context, MaterialPageRoute(builder: (context) {
      return StudentDetail(student, appTitle);
    }));
    if (result) {
      updateListView();
    }
  }
}

class StudentDetail extends StatefulWidget{
  String screenTitle;
  Student student;
  StudentDetail(this.student ,  this.screenTitle);
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return Students(this.student, screenTitle);
  }
}
class Students extends State<StudentDetail> {
  static var _level = ["Easy", "Medium","Hard"];
  static var _classes =["1st class", "2nd class","3rd class"];
  String screenTitle;
  Student student;
  SQL_Helper helper = new SQL_Helper();
  Students(this.student ,this.screenTitle);
  TextEditingController studentName = new TextEditingController();
  @override
  Widget build(BuildContext context) {
    TextStyle textStyle = Theme
        .of(context)
        .textTheme
        .title;
    studentName.text = student.name;
    // TODO: implement build
    return
      WillPopScope(
          onWillPop: () {
            debugPrint("WillPopScope Button");
            goBack();
          },
          child: Scaffold(
            appBar: AppBar(
              title: Text(screenTitle),
              leading: IconButton(
                icon: Icon(Icons.arrow_back),
                onPressed: () {
                  goBack();
                },
              ),
            ),
            body: Padding(
              padding: EdgeInsets.only(top: 15.0, left: 10.0, right: 10.0),
              child: ListView(
                children: <Widget>[
                  Padding(
                    padding: EdgeInsets.only(top: 15.0, bottom: 15.0),
                    child: TextField(
                      controller: studentName,
                      style: textStyle,
                      onChanged: (value) {
                        student.name = value;
                      },
                      decoration: InputDecoration(
                          labelText: "Name :",
                          labelStyle: textStyle,
                          border: OutlineInputBorder(
                            borderRadius: BorderRadius.circular(5.0),
                          )
                      ),
                    ),
                  ),
                  Row(
                    children: <Widget>[
                      SizedBox(width: 3),
                      Expanded(
                        child: DropdownButton(
                          isDense: true,
                          hint: Text('Level'),
                          isExpanded: true,
                          iconSize: 20,
                          items: _level.map((String dropDownStringItem) {
                            return DropdownMenuItem(
                              value: dropDownStringItem,
                              child: Text(dropDownStringItem),
                            );
                          }).toList(),
                          value: student.level == '' ? null : student.level,
                          onChanged: (String value) {
                            updateLevel(value);
                          },
                        ),
                      ),
                      SizedBox(width: 3),
                      Expanded(
                        child: DropdownButton(
                          isDense: true,
                          hint: Text('Class'),
                          isExpanded: true,
                          iconSize: 20,
                          items: _classes.map((String dropDownStringItem) {
                            return DropdownMenuItem(
                              value: dropDownStringItem,
                              child: Text(dropDownStringItem),
                            );
                          }).toList(),
                          value: student.classes == '' ? null : student.classes,
                          onChanged: (String value) {
                            updateClass(value);
                          },
                        ),
                      ),
                    ],
                  ),
                  Padding(
                    padding: EdgeInsets.only(top: 15.0, bottom: 15.0),
                    child: Row(
                      children: <Widget>[
                        Expanded(
                          child: RaisedButton(
                            color: Theme
                                .of(context)
                                .primaryColorDark,
                            textColor: Theme
                                .of(context)
                                .primaryColorLight,
                            child: Text(
                              'SAVE', textScaleFactor: 1.5,
                            ),
                            onPressed: () {
                              setState(() {
                                debugPrint("User Click SAVED");
                                _save();
                              });
                            },
                          ),
                        ),
                        Container(width: 5.0,),
                        Expanded(
                          child: RaisedButton(
                            color: Theme
                                .of(context)
                                .primaryColorDark,
                            textColor: Theme
                                .of(context)
                                .primaryColorLight,
                            child:
                            Text(
                              'Delete', textScaleFactor: 1.5,
                            ),
                            onPressed: () {
                              setState(() {
                                debugPrint("User Click Delete");
                                _delete();
                              });
                            },
                          ),
                        ),
                      ],
                    ),
                  )
                ],
              ),
            ),
          )
      );
  }
  void goBack() {
    Navigator.pop(context, true);
  }
  void updateLevel(String value) {
    setState(() {
      student.level = value;
    });
  }
  void updateClass(String value) {
    setState(() {
      student.classes = value;
    });
  }
  void _save() async {
    goBack();
    student.date = DateFormat.yMMMd().format(DateTime.now());
    int result;
    if (student.id == null) {
      result =  await helper.insertStudent(student);
    } else {
      result = await helper.updateStudent(student);
    }
    if (result == 0) {
      showAlertDialog('Sorry', "Student not saved");
    } else {
      showAlertDialog('Congratulations', 'Student has been saved successfully');
    }
  }
  void showAlertDialog(String title, String msg){
    AlertDialog alertDialog = AlertDialog(
      title: Text(title),
      content: Text(msg),
    );
    showDialog(context: context, builder: (_) => alertDialog);
  }

  void _delete() async {
    goBack();
    if (student.id == null){
      showAlertDialog('Ok Delete', "No student was deleted");
      return;
    }
    int result = await helper.deleteStudent(student.id);
    if (result == 0) {
      showAlertDialog('Ok Delete', "No student was deleted");
    } else {
      showAlertDialog('Ok Delete', "Student has been deleted");
    }
  }
}


class Menu extends StatefulWidget {
  @override
  _MenuState createState() => _MenuState();
}
class _MenuState extends State<Menu> {
  @override
  Widget build(BuildContext context) {
    return Container(
        color: Colors.tealAccent,
        padding: EdgeInsets.only(top:150),
        child: Center(
          child: GridView.count(
              crossAxisCount: 1,
              padding: EdgeInsets.all(50),
              children: <Widget>[
                Card(
                    margin: EdgeInsets.all(70.0),
                    child: InkWell(
                      onTap: (){
                        Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (context) => Questions()
                          ),
                        );
                      },
                      splashColor: Colors.deepPurple,
                      child: Center(
                        child: Column(
                          mainAxisSize: MainAxisSize.min,
                          children: <Widget>[
                            Icon(Icons.library_books, size:70.0, color:Colors.blue,),
                            Text("Questions List",style: new TextStyle(fontSize: 20.0,color: Colors.black , fontWeight: FontWeight.bold))
                          ],
                        ),
                      ),
                    )
                ),
              ]
          ),
        )
    );
  }
}

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, ) ,
              );
            },
          );
        },
      ),
    );
  }
}