大幅変更＆環境バージョンアップ

lib/services/DatabaseService.dart

@@ -0,0 +1,55 @@
+import 'dart:async';
+
+import 'package:gifunavi/model/destination.dart';
+import 'package:gifunavi/utils/database_helper.dart';
+
+class DatabaseService {
+  // Private constructor
+  DatabaseService._privateConstructor();
+
+  // Static instance
+  static final DatabaseService _instance =
+      DatabaseService._privateConstructor();
+
+  // Factory constructor to return the instance
+  factory DatabaseService() {
+    return _instance;
+  }
+
+  // StreamController for updates
+  final StreamController<List<Destination>> _dbUpdateController =
+      StreamController<List<Destination>>.broadcast();
+
+  // Getter for the stream
+  Stream<List<Destination>> get destinationUpdatesStream =>
+      _dbUpdateController.stream;
+
+  // Method to fetch destinations
+  Future<List<Destination>> fetchDestinations() async {
+    // Your database fetch logic here
+    List<Destination> destinations = await _fetchFromDb();
+    _dbUpdateController.add(destinations);
+    return destinations;
+  }
+
+  // Method to update the database and emit an update through the stream
+  Future<void> updateDatabase() async {
+    // Your update logic here
+
+    // After updating, fetch the updated list and add it to the stream
+    fetchDestinations();
+  }
+
+  // Method to fetch data from the database (placeholder)
+  Future<List<Destination>> _fetchFromDb() async {
+    // Simulate fetching data with a delay
+    DatabaseHelper db = DatabaseHelper.instance;
+    List<Destination> destinations = await db.getDestinations();
+    return destinations; // Replace with your actual fetch operation
+  }
+
+  // Dispose method to close the stream controller
+  void dispose() {
+    _dbUpdateController.close();
+  }
+}