refactor: move exportation functions to utils/

app/lib/pages/default_page.dart

@@ -64,10 +64,10 @@ class _DefaultPageState extends State<DefaultPage> {
                   delegate: CustomSearchDelegate((String result) {
                     // Make request only if the selected lake is different from the current selected lake
                     if (result != selectedLake) {
-                      initialiseState(false);
                       setState(() {
                         selectedLake = result;
                         // NB update lastLake persistent variable
+                        initialiseState(false);
                       });
                     }
                   }),

app/lib/utils/export_data.dart

+import 'dart:io';
+import 'dart:convert';
+import 'package:flutter/material.dart';
+import 'package:path_provider/path_provider.dart';
+
+import '../../consts.dart';
+
+
+// Saves all measurements to a file on the users mobile device
+Future<void> _exportIceData() async {
+  final directory = await getExternalStorageDirectory();
+  final file = File('${directory?.path}/ice_data_$selectedLake.json');
+
+  // Convert JSON data to string
+  final jsonString = jsonEncode(selectedMarkerList);
+
+  // Write JSON data to file
+  await file.writeAsString(jsonString);
+}
+
+
+// Display a progress indicator while JSON data is being downloaded
+void showProgressIndicator(BuildContext context) {
+  BuildContext? dialogContext;
+
+  showDialog(
+    context: context,
+    builder: (BuildContext context) {
+      dialogContext = context;
+
+      return WillPopScope(
+        onWillPop: () async => false, // Prevent dialog from being closed by user
+        child: const AlertDialog(
+          content: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              CircularProgressIndicator(), // Progress indicator
+              SizedBox(height: 20),
+              Text('Exporting JSON data...'),
+            ],
+          ),
+        ),
+      );
+    },
+  );
+
+  // Ensure that the progress indicator runs for at lest 1 second
+  Future.delayed(const Duration(seconds: 1), () {
+    try { // Download JSON data
+      _exportIceData();
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Downloaded ice data as JSON')),
+      );
+    } catch (e) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text('Failed to export JSON data: $e')),
+      );
+    } finally {
+      if (dialogContext != null) {
+        // Add 2 second delay before closing the dialog
+        Future.delayed(const Duration(seconds: 2), () {
+          Navigator.of(dialogContext!).pop();
+          Navigator.of(context).pop();
+        });
+      }
+    }
+  });
+}
+

app/lib/widgets/main_layout.dart

-import 'dart:io';
-import 'dart:convert';
 import 'dart:typed_data';
 import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
-import 'package:path_provider/path_provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 import 'osm_layer.dart';
@@ -13,6 +10,7 @@ import 'choropleth_map.dart';
 import '../data_classes.dart';
 import 'satellite_layer.dart';
 import 'quick_view_chart.dart';
+import '../utils/export_data.dart';
 import '../utils/format_month.dart';
 
 /// MapContainerWidget is the main widget that contains the map with all
@@ -291,66 +289,4 @@ class _MapContainerWidgetState extends State<MapContainerWidget> {
       },
     );
   }
-}
-
-// Saves all measurements to a file on the users mobile device
-Future<void> _exportIceData() async {
-  final directory = await getExternalStorageDirectory();
-  final file = File('${directory?.path}/ice_data_$selectedLake.json');
-
-  // Convert JSON data to string
-  final jsonString = jsonEncode(selectedMarkerList);
-
-  // Write JSON data to file
-  await file.writeAsString(jsonString);
-}
-
-
-// Display a progress indicator while JSON data is being downloaded
-void showProgressIndicator(BuildContext context) {
-  BuildContext? dialogContext;
-
-  showDialog(
-    context: context,
-    builder: (BuildContext context) {
-      dialogContext = context;
-
-      return WillPopScope(
-        onWillPop: () async => false, // Prevent dialog from being closed by user
-        child: const AlertDialog(
-          content: Column(
-            mainAxisSize: MainAxisSize.min,
-            children: [
-              CircularProgressIndicator(), // Progress indicator
-              SizedBox(height: 20),
-              Text('Exporting JSON data...'),
-            ],
-          ),
-        ),
-      );
-    },
-  );
-
-  // Ensure that the progress indicator runs for at lest 1 second
-  Future.delayed(const Duration(seconds: 1), () {
-    try { // Download JSON data
-      _exportIceData();
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('Downloaded ice data as JSON')),
-      );
-    } catch (e) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text('Error exporting JSON data: $e')),
-      );
-    } finally {
-      if (dialogContext != null) {
-        // Add 2 second delay before closing the dialog
-        Future.delayed(const Duration(seconds: 2), () {
-          Navigator.of(dialogContext!).pop();
-          Navigator.of(context).pop();
-        });
-      }
-    }
-  });
-}
-
+}
\ No newline at end of file