added comments and refactored code

lib/widgets/custom_marker.dart

@@ -1,13 +1,15 @@
 import 'package:flutter/material.dart';
 
 class CustomMarker extends StatelessWidget {
-  const CustomMarker({super.key, required this.onTap});
-  final void Function() onTap;
+  const CustomMarker({super.key, required void Function() onTap})
+      : _onTap = onTap;
+
+  final void Function() _onTap;
 
   @override
   Widget build(BuildContext context) {
     return GestureDetector(
-      onTap: onTap,
+      onTap: _onTap,
       child: Icon(
         Icons.location_on_sharp,
         color: Theme.of(context).colorScheme.primary,

lib/widgets/flood_station_list_view.dart

@@ -6,11 +6,12 @@ class FloodStationListView extends StatelessWidget {
   const FloodStationListView(
       {super.key,
       required List<FloodStation> stations,
-      required this.onItemTapped})
-      : _stations = stations;
+      required void Function(FloodStation) onItemTapped})
+      : _onItemTapped = onItemTapped,
+        _stations = stations;
 
   final List<FloodStation> _stations;
-  final void Function(FloodStation) onItemTapped;
+  final void Function(FloodStation) _onItemTapped;
 
   @override
   Widget build(BuildContext context) {
@@ -23,7 +24,7 @@ class FloodStationListView extends StatelessWidget {
         final item = _stations.elementAt(index);
         return ListTile(
           isThreeLine: true,
-          onTap: () => onItemTapped(item),
+          onTap: () => _onItemTapped(item),
           title: Text(item.label),
           subtitle: Column(
             crossAxisAlignment: CrossAxisAlignment.start,

lib/widgets/loading_notifier.dart

@@ -2,9 +2,14 @@ import 'package:flutter/material.dart';
 
 class LoadingNotifier extends StatelessWidget {
   const LoadingNotifier(
-      {super.key, required this.onDismissed, required this.message});
-  final void Function() onDismissed;
-  final String message;
+      {super.key,
+      required void Function() onDismissed,
+      required String message})
+      : _onDismissed = onDismissed,
+        _message = message;
+
+  final void Function() _onDismissed;
+  final String _message;
 
   @override
   Widget build(BuildContext context) {
@@ -26,11 +31,11 @@ class LoadingNotifier extends StatelessWidget {
                 child: CircularProgressIndicator(),
               ),
               Text(
-                message,
+                _message,
                 style: Theme.of(context).textTheme.titleSmall,
               ),
               IconButton(
-                onPressed: () => onDismissed(),
+                onPressed: () => _onDismissed(),
                 icon: Icon(Icons.close),
               )
             ],

lib/widgets/map_popup.dart

@@ -5,14 +5,19 @@ import '../model/flood_station.dart';
 
 class MapPopup extends StatelessWidget {
   const MapPopup(
-      {super.key, required this.station, required this.onShowTapped});
-  final FloodStation station;
-  final Function() onShowTapped;
+      {super.key,
+      required FloodStation station,
+      required dynamic Function() onShowTapped})
+      : _onShowTapped = onShowTapped,
+        _station = station;
+
+  final FloodStation _station;
+  final Function() _onShowTapped;
 
   @override
   Widget build(BuildContext context) {
     return AlertDialog(
-      title: Text(station.label),
+      title: Text(_station.label),
       content: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         mainAxisSize: MainAxisSize.min,
@@ -22,14 +27,14 @@ class MapPopup extends StatelessWidget {
             children: [
               Icon(Icons.home_outlined),
               Padding(padding: EdgeInsets.only(left: 8)),
-              Text(station.town.isEmpty ? '-' : station.town),
+              Text(_station.town.isEmpty ? '-' : _station.town),
             ],
           ),
           Row(
             children: [
               Icon(Icons.water),
               Padding(padding: EdgeInsets.only(left: 8)),
-              Text(station.riverName.isEmpty ? '-' : station.riverName),
+              Text(_station.riverName.isEmpty ? '-' : _station.riverName),
             ],
           ),
           Row(
@@ -37,8 +42,8 @@ class MapPopup extends StatelessWidget {
               Icon(Icons.calendar_month_outlined),
               Padding(padding: EdgeInsets.only(left: 8)),
               Text(
-                station.dateOpened != null
-                    ? intl.DateFormat.yMd().format(station.dateOpened!)
+                _station.dateOpened != null
+                    ? intl.DateFormat.yMd().format(_station.dateOpened!)
                     : '-',
               ),
             ],
@@ -51,7 +56,7 @@ class MapPopup extends StatelessWidget {
           child: Text('dismiss'),
         ),
         TextButton(
-          onPressed: onShowTapped,
+          onPressed: _onShowTapped,
           child: Text('show'),
         ),
       ],

lib/widgets/station_filter.dart

@@ -9,28 +9,28 @@ class StationFilter extends StatefulWidget {
 }
 
 class StationFilterState extends State<StationFilter> {
-  TextEditingController filterController = TextEditingController();
+  final TextEditingController _filterController = TextEditingController();
 
   @override
   Widget build(BuildContext context) {
     return TextField(
-      controller: filterController,
+      controller: _filterController,
       decoration: InputDecoration(
         prefixIcon: Icon(Icons.search),
         suffixIcon: Opacity(
-          opacity: filterController.text.isEmpty ? 0 : 1,
+          opacity: _filterController.text.isEmpty ? 0 : 1,
           child: IconButton(
             onPressed: () {
-              filterController.clear();
+              _filterController.clear();
 
-              widget.onChanged(filterController.text);
+              widget.onChanged(_filterController.text);
             },
             icon: Icon(Icons.delete),
           ),
         ),
         label: Text('Filter'),
       ),
-      onChanged: (_) => widget.onChanged(filterController.text),
+      onChanged: (_) => widget.onChanged(_filterController.text),
     );
   }
 }