add error for request get

covas_mobile/lib/MyHomePage.dart

@@ -3,6 +3,7 @@
 import 'dart:io';
 import 'dart:convert';
 
+import 'package:covas_mobile/classes/alert.dart';
 import 'package:flutter/material.dart';
 import 'package:http/http.dart' as http;
 import 'package:shared_preferences/shared_preferences.dart';
@@ -54,28 +55,72 @@ class MyHomePage extends StatefulWidget {
   State<MyHomePage> createState() => _MyHomePageState();
 }
 
-class _MyHomePageState extends State<MyHomePage> {
+class _MyHomePageState extends State<MyHomePage> with ShowErrorDialog {
   String listUser = "";
 
   Future<void> _incrementCounter() async {
     SharedPreferences prefs = await SharedPreferences.getInstance();
-    var user = prefs.getString("user");
+    var user = prefs.getString("user") ?? "";
-    var jwt = prefs.getString("jwt");
+    var jwt = prefs.getString("jwt") ?? "";
     String former = "";
-    stderr.writeln("User ${user}");
-    stderr.writeln("Jwt ${jwt}");
 
+    if ((user.isNotEmpty) && (jwt.isNotEmpty)) {
       var urlGet = Uri.parse("http://localhost:8083/api/users");
 
       var responseGet = await http
           .get(urlGet, headers: {HttpHeaders.cookieHeader: '${jwt}; ${user}'});
 
       stderr.writeln('Response Get status: ${responseGet.statusCode}');
+      if (responseGet.statusCode == 200) {
         stderr.writeln('Response Get body: ${responseGet.body}');
         var json = jsonDecode(responseGet.body);
         for (var user in json) {
           former = "$former\n ${user['name']}";
         }
+      } else {
+        var text = "";
+        switch (responseGet.statusCode) {
+          case 400:
+            {
+              text = "Requête mal construite";
+            }
+            break;
+          case 406:
+            {
+              text = "Mot de passe incorrect";
+            }
+            break;
+          case 404:
+            {
+              text = "Utilisateur inconnu";
+            }
+            break;
+          case 403:
+            {
+              text = "Utilisateur desactive";
+            }
+            break;
+          case 410:
+            {
+              text = "Token invalide";
+            }
+            break;
+          case 500:
+            {
+              text = "Probleme interne du serveur";
+            }
+            break;
+          default:
+            {
+              text = "Probleme d'authentification inconnu";
+            }
+            break;
+        }
+        showErrorDialog(context, text);
+      }
+    } else {
+      showErrorDialog(context, "Cache invalide");
+    }
 
     setState(() {
       // This call to setState tells the Flutter framework that something has

covas_mobile/lib/classes/alert.dart

@@ -1,7 +1,8 @@
 import 'package:flutter/material.dart';
+
 import '../main.dart';
 
-mixin ShowErrorDialog on State<LoginDemo> {
+mixin ShowErrorDialog<T extends StatefulWidget> on State<T> {
   void showErrorDialog(BuildContext context, String text) {
     // Create AlertDialog
     AlertDialog dialog = AlertDialog(