add: network_controller.dart

app/lib/controller/network_controller.dart

+import 'package:get/get.dart';
+import 'package:flutter/material.dart';
+import 'package:connectivity_plus/connectivity_plus.dart';
+
+import '../consts.dart';
+
+/// NetworkController checks the network connection of the application globally
+class NetworkController extends GetxController {
+  final Connectivity _connectivity = Connectivity();
+
+  @override
+  void onInit() {
+    super.onInit();
+    _connectivity.onConnectivityChanged.listen(_updateConnectionStatus);
+  }
+
+  void _updateConnectionStatus(ConnectivityResult connectivityResult) {
+
+    // If no network connection, show snack-bar
+    if (connectivityResult == ConnectivityResult.none) {
+      Get.rawSnackbar(
+        messageText: Text(
+          'You are not connected to the internet. The displayed information may be inaccurate.',
+            style: regTextStyle,
+        ),
+        isDismissible: false,
+        duration: const Duration(days: 1), // Display the message until a network connection is established
+        backgroundColor: Colors.black45,
+        icon: const Icon(
+          Icons.wifi_off,
+          color: Colors.white,
+          size: 35,
+        ),
+        margin: EdgeInsets.zero,
+        snackStyle: SnackStyle.GROUNDED,
+      );
+    } else {
+      if (Get.isSnackbarOpen) { // Close snack-bar upon establishing internet connection
+        Get.closeCurrentSnackbar();
+      }
+    }
+  }
+}
\ No newline at end of file

app/lib/server_requests/init_state.dart

@@ -9,37 +9,47 @@ import '../server_requests/fetch_markers.dart';
 import '../server_requests/fetch_relation.dart';
 
 
-Future<void> initialiseState() async{
+/// initialiseState makes three requests to the server, one requesting
+/// measurements for the selected relation, the other requesting the relation,
+/// and the last requesting the list of all system lakes
+Future<void> initialiseState() async {
   bool serverConnection = true;
 
   late Future<List<Measurement>> markerListFuture;
   late Future<Uint8List> relationFuture;
 
-  // Try to fetch measurement data from server
-  markerListFuture = fetchMeasurements().then((fetchResult) {
-    List<Measurement> measurements = fetchResult.measurements;
-    serverConnection = fetchResult.connected;
+  try {
+    // Try to fetch measurement data from server
+    markerListFuture = fetchMeasurements().then((fetchResult) {
+      List<Measurement> measurements = fetchResult.measurements;
+      serverConnection = fetchResult.connected;
 
-    // Return the measurements
-    return measurements;
-  }).catchError((error) {
-    serverConnection = false;
-    throw Exception("Failed to fetch measurements: $error");
-  });
+      // Return measurements
+      return measurements;
+    }).catchError((error) {
+      serverConnection = false;
+      throw Exception("Failed to fetch measurements: $error");
+    });
 
-  // Attempt to fetch relation from server if app establishes connection
-  if (serverConnection) {
-    relationFuture = fetchRelation();
-  } else { // Read last saved data
-    relationFuture = loadSavedRelation();
-  }
+    // If measurements were fetched successfully, request relation
+    if (serverConnection) {
+      relationFuture = fetchRelation();
+    } /*else { // Read last saved data
+      relationFuture = loadSavedRelation();
+    }*/
 
-  initSearchOptions();
+    initSearchOptions();
 
-  selectedRelation = await relationFuture;
-  selectedMarkerList = await markerListFuture;
+    //selectedRelation = await relationFuture;
+    selectedRelation = Uint8List(0);
+    selectedMarkerList = await markerListFuture;
+  } catch (e) {
+    // Handle any errors that occur during the initialization process
+    print("Error during initialization: $e");
+  }
 }
 
+
 /// initSearchOptions fetches a list of all lake names in the system
 /// and initialises lakeSearchOptions
 Future<void> initSearchOptions() async {

app/pubspec.lock

 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
+  args:
+    dependency: transitive
+    description:
+      name: args
+      sha256: eef6c46b622e0494a36c5a12d10d77fb4e855501a91c1b9ef9339326e58f0596
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.4.2"
   async:
     dependency: transitive
     description:
@@ -41,6 +49,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.18.0"
+  connectivity_plus:
+    dependency: "direct main"
+    description:
+      name: connectivity_plus
+      sha256: b74247fad72c171381dbe700ca17da24deac637ab6d43c343b42867acb95c991
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.6"
+  connectivity_plus_platform_interface:
+    dependency: transitive
+    description:
+      name: connectivity_plus_platform_interface
+      sha256: cf1d1c28f4416f8c654d7dc3cd638ec586076255d407cef3ddbdaf178272a71a
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.4"
   crypto:
     dependency: transitive
     description:
@@ -49,6 +73,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.3"
+  dbus:
+    dependency: transitive
+    description:
+      name: dbus
+      sha256: "365c771ac3b0e58845f39ec6deebc76e3276aa9922b0cc60840712094d9047ac"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.7.10"
   equatable:
     dependency: transitive
     description:
@@ -128,6 +160,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.5.1"
+  get:
+    dependency: "direct main"
+    description:
+      name: get
+      sha256: e4e7335ede17452b391ed3b2ede016545706c01a02292a6c97619705e7d2a85e
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.6.6"
   google_fonts:
     dependency: "direct main"
     description:
@@ -160,6 +200,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.19.0"
+  js:
+    dependency: transitive
+    description:
+      name: js
+      sha256: f2c445dce49627136094980615a031419f7f3eb393237e4ecd97ac15dea343f3
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.6.7"
   latlong2:
     dependency: "direct main"
     description:
@@ -248,6 +296,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.0"
+  nm:
+    dependency: transitive
+    description:
+      name: nm
+      sha256: "2c9aae4127bdc8993206464fcc063611e0e36e72018696cd9631023a31b24254"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.5.0"
   path:
     dependency: transitive
     description:
@@ -328,6 +384,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.11.1"
+  petitparser:
+    dependency: transitive
+    description:
+      name: petitparser
+      sha256: c15605cd28af66339f8eb6fbe0e541bfe2d1b72d5825efc6598f3e0a31b9ad27
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.0.2"
   platform:
     dependency: transitive
     description:
@@ -573,6 +637,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.4"
+  xml:
+    dependency: transitive
+    description:
+      name: xml
+      sha256: b015a8ad1c488f66851d762d3090a21c600e479dc75e68328c52774040cf9226
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.5.0"
 sdks:
   dart: ">=3.3.0 <4.0.0"
   flutter: ">=3.19.0"

app/pubspec.yaml

@@ -9,9 +9,9 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
-  flutter_map: ^4.0.0                 # Various maps
+  flutter_map: ^4.0.0                 # Maps ans map customization
   http: ^0.13.3                       # HTTPS requests
-  latlong2: ^0.8.2
+  latlong2: ^0.8.2                    # LatLng object
   provider: ^5.0.0
   fl_chart: ^0.20.0-nullsafety1       # Charts and diagrams
   google_fonts: any                   # Fonts
@@ -20,6 +20,8 @@ dependencies:
   path_provider: ^2.0.8
   shared_preferences: any             # Persistent data storage
   fuzzy: any                          # Search algorithm
+  connectivity_plus: ^3.0.3           # Check internet connection
+  get: ^4.6.5
 
 dev_dependencies:
   flutter_test: