Refactor excursion_main.dart to implement a confirmation dialog on page exit, allowing users to save templates or exit without saving. Update TrackingService to support instance reset for better state management.

lib/screens/excursion/excursion_main.dart

@@ -458,96 +458,148 @@ class _ExcursionMainState extends State<ExcursionMain> {
           ),
         ];
 
-    // Begin of widget tree
+    return PopScope(
-    return Scaffold(
+      canPop: false,
-      appBar: AppBar(
+      onPopInvoked: (didPop) async {
-        title: Text(AppLocalizations.of(context)!.excursion),
+        if (didPop) {
-        actions: [
+          return;
-          // Text(TrackingService().isTracking ? "Tracking" : "Not tracking")
+        }
-          Image.asset(
+        
-            TrackingService().isTracking ? "assets/icons/tracking_on.png" : "assets/icons/tracking_off.png",
+        // Show confirmation dialog
-            width: 40,
+        final result = await showDialog<int>(
-            ),
+          context: context,
-        ],
+          builder: (context) => AlertDialog(
-      ),
+            title: const Text('Seite verlassen?'),
-      body: PageTransitionSwitcher(
+            content: const Text('Möchten Sie die Seite wirklich verlassen?'),
-        duration: const Duration(microseconds: 800),
+            actions: [
-        transitionBuilder: (
+              TextButton(
-          Widget child,
+                onPressed: () => Navigator.of(context).pop(0),
-          Animation<double> animation,
+                child: const Text('Nein'),
-          Animation<double> secondaryAnimation,
+              ),
-        ) {
+              TextButton(
-          return SharedAxisTransition(
+                onPressed: () => Navigator.of(context).pop(1),
-            animation: animation,
+                child: const Text('Ja und Template speichern'),
-            secondaryAnimation: secondaryAnimation,
+              ),
-            transitionType: SharedAxisTransitionType.vertical,
+              TextButton(
-            child: child,
+                onPressed: () => Navigator.of(context).pop(2),
-          );
+                child: const Text('Ja ohne Template'),
-        },
+              ),
-        child: Stepper(
+            ],
-          key: ValueKey<int>(currentStep),
+          ),
-          steps: getSteps(),
+        );
-          currentStep: currentStep,
+
-          onStepTapped: (value) {
+        if (result == null || result == 0) {
-            setState(() {
+          return;
-              currentStep = value;
+        } else if (result == 1) {
-            });
+          // Save as template and leave
+          if (context.mounted) {
+            saveTemplate(
+              getFieldsText(),
+              DatabasesEnum.excursion,
+            );
+          }
+          TrackingService.resetInstance();
+          if (context.mounted) {
+            Navigator.of(context).pop();
+          }
+        } else {
+          // Just leave without saving
+          TrackingService.resetInstance();
+          if (context.mounted) {
+            Navigator.of(context).pop();
+          }
+        }
+      },
+      child: Scaffold(
+        appBar: AppBar(
+          title: Text(AppLocalizations.of(context)!.excursion),
+          actions: [
+            // Text(TrackingService().isTracking ? "Tracking" : "Not tracking")
+            Image.asset(
+              TrackingService().isTracking ? "assets/icons/tracking_on.png" : "assets/icons/tracking_off.png",
+              width: 40,
+              ),
+          ],
+        ),
+        body: PageTransitionSwitcher(
+          duration: const Duration(microseconds: 800),
+          transitionBuilder: (
+            Widget child,
+            Animation<double> animation,
+            Animation<double> secondaryAnimation,
+          ) {
+            return SharedAxisTransition(
+              animation: animation,
+              secondaryAnimation: secondaryAnimation,
+              transitionType: SharedAxisTransitionType.vertical,
+              child: child,
+            );
           },
-          onStepContinue: () async {
+          child: Stepper(
-            final isLastStep = currentStep == getSteps().length - 1;
+            key: ValueKey<int>(currentStep),
-
+            steps: getSteps(),
-            if (!isLastStep) {
+            currentStep: currentStep,
-              var res = await saveTemplate(
+            onStepTapped: (value) {
-                getFieldsText(),
-                DatabasesEnum.excursion,
-              );
-
-              isTemplate = true;
               setState(() {
-                rmap["ID"]!["controller"]!.text = res.toString();
+                currentStep = value;
-                currentStep += 1;
               });
-            } else {
+            },
-              if (widget.isSent) {
+            onStepContinue: () async {
-                Navigator.pushNamedAndRemoveUntil(
+              final isLastStep = currentStep == getSteps().length - 1;
-                  context,
-                  '/home',
-                  (route) => false,
-                );
-                return;
-              }
 
-              bool empty = CheckRequired.checkRequired(rmap);
+              if (!isLastStep) {
-              // for debugging always false
+                var res = await saveTemplate(
-              // empty = false;
-
-              if (empty) {
-                AddEntriesDialogHelper.showTemplateDialog(
-                  context,
                   getFieldsText(),
                   DatabasesEnum.excursion,
                 );
-                return;
+
+                isTemplate = true;
+                setState(() {
+                  rmap["ID"]!["controller"]!.text = res.toString();
+                  currentStep += 1;
+                });
               } else {
-                bool pop = await AddEntriesDialogHelper.showSaveOptionsDialog(
+                if (widget.isSent) {
-                  context,
+                  Navigator.pushNamedAndRemoveUntil(
-                  getFieldsText(),
+                    context,
-                  widget.isTemplate,
+                    '/home',
-                  DatabasesEnum.excursion,
+                    (route) => false,
-                );
+                  );
-                if (pop && context.mounted) Navigator.of(context).pop();
+                  return;
+                }
+
+                bool empty = CheckRequired.checkRequired(rmap);
+                // for debugging always false
+                // empty = false;
+
+                if (empty) {
+                  AddEntriesDialogHelper.showTemplateDialog(
+                    context,
+                    getFieldsText(),
+                    DatabasesEnum.excursion,
+                  );
+                  return;
+                } else {
+                  bool pop = await AddEntriesDialogHelper.showSaveOptionsDialog(
+                    context,
+                    getFieldsText(),
+                    widget.isTemplate,
+                    DatabasesEnum.excursion,
+                  );
+                  if (pop && context.mounted) Navigator.of(context).pop();
+                }
               }
-            }
+            },
-          },
+            onStepCancel: () {
-          onStepCancel: () {
+              if (currentStep == 0) {
-            if (currentStep == 0) {
+                Navigator.pop(context);
-              Navigator.pop(context);
+              } else {
-            } else {
+                setState(() {
-              setState(() {
+                  currentStep -= 1;
-                currentStep -= 1;
+                });
-              });
+              }
-            }
+            },
-          },
+          ),
         ),
       ),
     );

lib/services/tracking_service.dart

@@ -9,10 +9,22 @@ import 'package:latlong2/latlong.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 class TrackingService {
-  static final TrackingService _instance = TrackingService._internal();
+  static TrackingService? _instance;
-  factory TrackingService() => _instance;
+  
+  factory TrackingService() {
+    _instance ??= TrackingService._internal();
+    return _instance!;
+  }
+  
   TrackingService._internal();
 
+  static void resetInstance() {
+    if (_instance != null) {
+      _instance!.dispose();
+      _instance = null;
+    }
+  }
+
   List<LatLng> pathList = [];
   List<double> accuracyList = [];
   Timer? _positionTimer;