1°) Utilisation du type MAP :
Les données map dans Dart sont une collection de paires clé-valeur. Chaque valeur est associée à une clé, ce qui signifie que chaque clé doit être unique, mais la même valeur peut être utilisée plusieurs fois . Deux éléments possédant la même valeur resteront uniques en ayant des clés distinctes.
var nombres = Map<int, String>();
nombres[1] = "Un";
nombres[2] = "Deux";
nombres[3] = "Trois";
nombres[4] = "Quatre";
print("nombres = $nombres");
Donne : nombres = {1: Un, 2: Deux, 3: Trois, 4: Quatre}
print(nombres.length);
Donne : 4
Pour afficher toutes les clefs et les valeurs :
print("Les clés sont : ${nombre.keys}");
print("Les valeurs sont : ${mombre.values}");
MAP dynamic :
Références :
2°) Utilisation du JSON :
JavaScript Object Notation (JSON) est un format de données textuelles dérivé de la notation des objets du langage JavaScript. Il permet de représenter de l’information structurée. Très utilisé pour les APIs
Références :
https://codewithandrea.com/articles/parse-json-dart/
3°) Récupération du résultat d’une API (liste de données) :
Référence : https://docs.flutter.dev/cookbook/networking/fetch-data
import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
Future<List<Album>> fetchAlbum() async {
final response =
await http.get(Uri.parse('https://jsonplaceholder.typicode.com/albums'));
// Reponse is a list of data Json [{"userId": 1,"id": 1,"title": "quidem molestiae enim"},
// {"userId": 2,"id": 2,"title": "sunt qui excepturi placeat culpa"},
if (response.statusCode == 200) {
// If the server did return a 200 OK response, then parse the JSON.
Iterable l = json.decode(response.body);
List<Album> posts =
List<Album>.from(l.map((model) => Album.fromJson(model)));
//print(posts[0].title);
return (posts);
} else {
// If the server did not return a 200 OK response, then throw an exception.
throw Exception('Failed to load album');
}
}
class Album {
final int userId;
final int id;
final String title;
const Album({
required this.userId,
required this.id,
required this.title,
});
factory Album.fromJson(Map<String, dynamic> json) {
return Album(
userId: json['userId'],
id: json['id'],
title: json['title'],
);
}
}
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Fetch Data Example',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: const Text('Fetch Data Example'),
),
body: Center(
child: FutureBuilder(
future: fetchAlbum(),
builder: (context, AsyncSnapshot snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.waiting: return Center(child: CircularProgressIndicator());
default:
if (snapshot.hasError)
return Text('Error: ${snapshot.error}');
else
return //Text('Result: ${snapshot.data}');
ListView.builder(
itemCount: snapshot.data.length,
// scrollDirection: Axis.horizontal,
itemBuilder: (BuildContext context, int index) {
return Text('${snapshot.data[index].title}');
});
}
},
),
),
),
);
}
}Stockage du résultat de l’API dans une base de données :
AndroidManifest.xml :
<uses-permission android:name="android.permission.INTERNET" />pubsepc.yaml :
sqflite: ^2.0.2
path_provider: ^2.0.9
http: ^0.13.4Fichier stationsclass.dart :
import 'dart:convert';
class Radios {
Radios({
required this.userId,
required this.id,
required this.title,
});
int userId;
int id;
String title;
factory Radios.fromMap(Map<String, dynamic> json) => Radios(
userId: json["userId"],
id: json["id"],
title: json["title"],
);
Map<String, dynamic> toMap() => {
"userId": userId,
"id": id,
"title": title,
};
}
Fichier Sqlite.dart
import 'dart:convert';
import "dart:io" as io;
import 'package:androdblite/stationsclass.dart';
import "package:path/path.dart";
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
import 'package:http/http.dart' as http;
class SqliteDB {
static final SqliteDB _instance = new SqliteDB.internal();
factory SqliteDB() => _instance;
static Database? _db;
Future<Database?> get db async {
if (_db != null) {
return _db;
}
_db = await initDb();
return _db;
}
SqliteDB.internal();
/// Initialize DB
initDb() async {
io.Directory documentDirectory = await getApplicationDocumentsDirectory();
String path = join(documentDirectory.path, "RadiosStations.db");
var taskDb = await openDatabase( //open the database or create a database if there isn't any
path,
version: 1,
onCreate: (Database db,int version) async{
await db.execute("""
CREATE TABLE Radios(
id INTEGER,
userid INTEGER,
title TEXT)"""
);
});
return taskDb;
//Pour id automatique : id INTEGER PRIMARY KEY AUTOINCREMENT,
}
/// Batch insert data
//-- Save API Result in DataBase
Future StoreDataList(String lignesJson) async {
List JsonList = json.decode(lignesJson);
final dbClient = await SqliteDB().db;
/// Initialize batch
final batch = dbClient?.batch();
JsonList.forEach((val) {
Radios ligneradio = Radios.fromMap(val);
batch!.insert("Radios", ligneradio.toMap());
//print(ligneradio.toMap());
});
/// Commit
await batch!.commit(noResult: true);
return "success";
}
//////////////////
// Retrieve all the data stored in dB
Future<List<Radios>> retrieveAllRadios() async{ //returns the memos as a list (array)
//-- Delete data if exists
await deleteAll();
//-- First, fetch the Data from the API and Store it in the DataBase
await ReadWriteDataList();
//-- Then display the DataBase
final db = await initDb();
final maps = await db.query("Radios"); //query all the rows in a table as an array of maps
//await db.close();
return List.generate(maps.length, (i) { //create a list of memos
return Radios(
id: maps[i]['id'] as int,
userId: maps[i]['userid'] as int,
title: maps[i]['title'] as String,
);
});
}
/// Get all users using raw query
Future getAll() async {
var dbClient = await SqliteDB().db;
final res = await dbClient?.rawQuery("SELECT * FROM Radios");
return res;
}
/// Simple query with WHERE raw query
Future getAdults() async {
var dbClient = await SqliteDB().db;
final res = await dbClient?.rawQuery("SELECT id, name FROM Radios WHERE age > 18");
return res;
}
/// deleteAllDatas
Future deleteAll() async {
var dbClient = await SqliteDB().db;
final res = await dbClient?.rawQuery("DELETE from Radios");
return res;
}
//::::::::::::::::::::::::::::
Future ReadWriteDataList() async {
//-- Initialize sq-lite
final db = await initDb();
final response =
await http.get(Uri.parse('https://jsonplaceholder.typicode.com/albums'));
// Reponse is a list of data Json [{"userId": 1,"id": 1,"title": "quidem molestiae enim"},
// {"userId": 2,"id": 2,"title": "sunt qui excepturi placeat culpa"},
if (response.statusCode == 200) {
// If the server did return a 200 OK response, then parse the JSON.
String resApi = response.body;
//print (resApi);
//-- Insert Data into DB
await StoreDataList(resApi);
} else {
// If the server did not return a 200 OK response, then throw an exception.
throw Exception('Failed to load data');
}
}
}Fichier main.dart :
import 'dart:async';
import 'dart:convert';
import 'package:androdblite/stationsclass.dart';
import 'package:flutter/material.dart';
import 'package:androdblite/sqlite.dart';
//////////
// Retrieve Data from API, store it in a database
// Display data from the database
//////
void main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
//-- Initialize sq-lite
final db = SqliteDB();
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Fetch Data Example',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: const Text('Fetch Data Example'),
),
body: Center(
child: FutureBuilder(
future: db.retrieveAllRadios(), //fetchAlbum(),
builder: (context, AsyncSnapshot snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.waiting: return Center(child: CircularProgressIndicator());
default:
if (snapshot.hasError)
return Text('Error: ${snapshot.error}');
else
return //Text('Result: ${snapshot.data}');
ListView.builder(
itemCount: snapshot.data.length,
// scrollDirection: Axis.horizontal,
itemBuilder: (BuildContext context, int index) {
return Text('${snapshot.data[index].title}');
});
}
},
),
),
),
);
}
}https://www.kindacode.com/article/how-to-fetch-data-from-apis-in-flutter/
Affichage de données d’une base dans une listview :
….
Future<List<Employee>> getEmployees() async {
var dbClient = await db;
List<Map> list = await dbClient.rawQuery('SELECT * FROM Employee');
List<Employee> employees = new List();
for (int i = 0; i < list.length; i++) {
employees.add(new Employee(list[i]["firstname"], list[i]["lastname"], list[i]["mobileno"], list[i]["emailid"]));
}
print(employees.length);
return employees;
}
https://www.kindacode.com/article/flutter-sqlite/
AndroLogiciels 