### Install geoflutterfire_plus

Source: https://pub.dev/packages/geoflutterfire_plus

Commands to add the package to a Flutter project.

```bash
flutter pub add geoflutterfire_plus
```

```yaml
dependencies:
  geoflutterfire_plus: <latest-version>
```

--------------------------------

### Example State Management

Source: https://pub.dev/packages/geoflutterfire_plus/example

Manages the state for the example page, including the set of markers displayed on the map and the current geographic query conditions.

```dart
class ExampleState extends State<Example> {
  /// [Marker]s on Google Maps.
  Set<Marker> _markers = {};

  /// [BehaviorSubject] of currently geo query radius and camera position.
  final _geoQueryCondition = BehaviorSubject<_GeoQueryCondition>.seeded(
    _GeoQueryCondition(
      radiusInKm: _initialRadiusInKm,
      cameraPosition: _initialCameraPosition,
    ),
  );

  /// [Stream] of geo query result.
  late final Stream<List<DocumentSnapshot<Map<String, dynamic>>>> _stream = 
      _geoQueryCondition.switchMap(
    (geoQueryCondition) => 
        GeoCollectionReference(_collectionReference).subscribeWithin(
      center: GeoFirePoint(
        GeoPoint(
          _cameraPosition.target.latitude,
          _cameraPosition.target.longitude,
        ),
      ),
      radiusInKm: geoQueryCondition.radiusInKm,
      field: 'geo',
      geopointFrom: (data) => 
          (data['geo'] as Map<String, dynamic>)['geopoint'] as GeoPoint,
      strictMode: true,
    ),
  );

  /// Updates [_markers] by fetched geo [DocumentSnapshot]s.
  void _updateMarkersByDocumentSnapshots(
    List<DocumentSnapshot<Map<String, dynamic>>> documentSnapshots,
  ) {
    final markers = <Marker>{};
    for (final ds in documentSnapshots) {
      final id = ds.id;
      final data = ds.data();
      if (data == null) {
        continue;
      }
      final name = data['name'] as String;
      final geoPoint = 
          (data['geo'] as Map<String, dynamic>)['geopoint'] as GeoPoint;
      markers.add(_createMarker(id: id, name: name, geoPoint: geoPoint));
    }
    debugPrint('📍 markers count: ${markers.length}');
    setState(() {
      _markers = markers;
    });
  }

  /// Creates a [Marker] by fetched geo location.
  Marker _createMarker({
    required String id,
    required String name,
    required GeoPoint geoPoint,
  }) => 
      Marker(
        markerId: MarkerId('(${geoPoint.latitude}, ${geoPoint.longitude})'),
        position: LatLng(geoPoint.latitude, geoPoint.longitude),
        infoWindow: InfoWindow(title: name),
        onTap: () => showDialog<void>(
          context: context,
          builder: (context) => SetOrDeleteLocationDialog(
            id: id,
            name: name,
            geoFirePoint: GeoFirePoint(
              GeoPoint(geoPoint.latitude, geoPoint.longitude),
            ),
          ),
        ),
      );

  /// Current detecting radius in kilometers.
  double get _radiusInKm => _geoQueryCondition.value.radiusInKm;

  /// Current camera position on Google Maps.
  CameraPosition get _cameraPosition => _geoQueryCondition.value.cameraPosition;

  /// Initial geo query detection radius in km.
  static const double _initialRadiusInKm = 1;

  /// Google Maps initial camera zoom level.

```

--------------------------------

### App Widget Setup

Source: https://pub.dev/packages/geoflutterfire_plus/example

Configures the root MaterialApp widget for the Flutter application, setting up the theme and the initial home screen.

```dart
class App extends StatelessWidget {
  const App({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        sliderTheme: SliderThemeData(
          overlayShape: SliderComponentShape.noOverlay,
        ),
      ),
      home: const Example(),
      // See using with converter example by removing comment below:
      // home: const WithConverterExample(),
      // See adding custom queries example by removing comment below:
      // home: const AdditionalQueryExample(),
      // home: const GeoFlutterFire2Example(),
    );
  }
}
```

--------------------------------

### Import geoflutterfire_plus in Dart

Source: https://pub.dev/packages/geoflutterfire_plus/install

Import the geoflutterfire_plus library into your Dart files to start using its functionalities.

```dart
import 'package:geoflutterfire_plus/geoflutterfire_plus.dart';
```

--------------------------------

### Initialize GoogleMap with GeoFlutterFire Plus

Source: https://pub.dev/packages/geoflutterfire_plus/example

Configures the initial state of the GoogleMap widget, including camera position and event listeners for map interactions. The `onMapCreated` callback starts listening to a stream for document snapshot updates.

```dart
GoogleMap(
            zoomControlsEnabled: false,
            myLocationButtonEnabled: false,
            initialCameraPosition: _initialCameraPosition,
            onMapCreated: (_) =>
                _stream.listen(_updateMarkersByDocumentSnapshots),
            markers: _markers,
            circles: {
              Circle(
                circleId: const CircleId('value'),
                center: LatLng(
                  _cameraPosition.target.latitude,
                  _cameraPosition.target.longitude,
                ),
                // multiple 1000 to convert from kilometers to meters.
                radius: _radiusInKm * 1000,
                fillColor: Colors.black12,
                strokeWidth: 0,
              ),
            },
            onCameraMove: (cameraPosition) {
              debugPrint('📷 lat: ${cameraPosition.target.latitude}, ' 
                  'lng: ${cameraPosition.target.latitude}');
              _geoQueryCondition.add(
                _GeoQueryCondition(
                  radiusInKm: _radiusInKm,
                  cameraPosition: cameraPosition,
                ),
              );
            },
            onLongPress: (latLng) => showDialog<void>(
              context: context,
              builder: (context) => AddLocationDialog(latLng: latLng),
            ),
          )
```

--------------------------------

### Add geoflutterfire_plus to pubspec.yaml

Source: https://pub.dev/packages/geoflutterfire_plus/install

This is an example of how the geoflutterfire_plus dependency will appear in your pubspec.yaml file after running `flutter pub add`.

```yaml
dependencies:
  geoflutterfire_plus: ^0.0.34
```

--------------------------------

### Firestore Collection and Geopoint Extraction

Source: https://pub.dev/packages/geoflutterfire_plus

Get a reference to your Firestore collection and define a function to extract GeoPoint data from documents.

```dart
// Reference to locations collection.
final CollectionReference<Map<String, dynamic>> collectionReference =
    FirebaseFirestore.instance.collection('locations');

// Function to get GeoPoint instance from Cloud Firestore document data.
GeoPoint geopointFrom(Map<String, dynamic> data) =>
     (data['geo'] as Map<String, dynamic>)['geopoint'] as GeoPoint;
```

--------------------------------

### Initialize Firebase and Run App

Source: https://pub.dev/packages/geoflutterfire_plus/example

Sets up Firebase initialization and runs the main application widget. Ensure Firebase is initialized before running the app.

```dart
void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
  runApp(const App());
}
```

--------------------------------

### Define package prerequisites

Source: https://pub.dev/packages/geoflutterfire_plus

Minimum Dart and Flutter SDK versions required for the package.

```text
Dart: '>=2.17.0 <3.0.0'
Flutter: '>=2.10.0'
```

--------------------------------

### Perform Basic Geo-Query

Source: https://pub.dev/packages/geoflutterfire_plus

Subscribe to a stream of document snapshots within a specified radius from the center point.

```dart
// Streamed document snapshots of geo query under given conditions.
final Stream<List<DocumentSnapshot<Map<String, dynamic>>>> stream =
    GeoCollectionReference<Map<String, dynamic>>(collectionReference)
        .subscribeWithin(
  center: center,
  radiusInKm: radiusInKm,
  field: field,
  geopointFrom: geopointFrom,
);
```

--------------------------------

### Create GeoFirePoint data

Source: https://pub.dev/packages/geoflutterfire_plus

Instantiate a GeoFirePoint and retrieve the map containing the GeoPoint and Geohash.

```dart
// Define GeoFirePoint by instantiating GeoFirePoint with latitude and longitude.
final GeoFirePoint geoFirePoint = GeoFirePoint(GeoPoint(35.681236, 139.767125));

// Gets GeoPoint instance and Geohash string as Map<String, dynamic>.
final Map<String, dynamic> data = geoFirePoint.data;

// {geopoint: Instance of 'GeoPoint', geohash: xn76urx66}
print(data);
```

--------------------------------

### Debug Window UI for GeoFlutterFire Plus

Source: https://pub.dev/packages/geoflutterfire_plus/example

Displays a debug overlay on the map showing the current marker count, radius, and a slider to adjust the search radius. This UI helps in visualizing and interacting with the geo-query parameters.

```dart
Container(
            width: double.infinity,
            margin: const EdgeInsets.only(top: 64, left: 16, right: 16),
            padding: const EdgeInsets.all(16),
            decoration: const BoxDecoration(
              color: Colors.black38,
              borderRadius: BorderRadius.all(Radius.circular(8)),
            ),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.start,
              mainAxisSize: MainAxisSize.min,
              children: [
                const Text(
                  'Debug window',
                  style: TextStyle(
                    color: Colors.white,
                    fontWeight: FontWeight.bold,
                  ),
                ),
                const SizedBox(height: 8),
                Text(
                  'Currently detected count: ' 
                  '${_markers.length}',
                  style: const TextStyle(color: Colors.white),
                ),
                const SizedBox(height: 8),
                Text(
                  'Current radius: ' 
                  '${_radiusInKm.toStringAsFixed(1)} (km)',
                  style: const TextStyle(color: Colors.white),
                ),
                const SizedBox(height: 8),
                Slider(
                  value: _radiusInKm,
                  min: 1,
                  max: 100,
                  divisions: 99,
                  label: _radiusInKm.toStringAsFixed(1),
                  onChanged: (value) => _geoQueryCondition.add(
                    _GeoQueryCondition(
                      radiusInKm: value,
                      cameraPosition: _cameraPosition,
                    ),
                  ),
                ),
              ],
            ),
          )
```

--------------------------------

### Define GeoFirePoint and Query Parameters

Source: https://pub.dev/packages/geoflutterfire_plus

Set up the center point, radius, and the Firestore field containing geohash data for your geo-query.

```dart
// cloud_firestore [GeoPoint] of Tokyo Station.
const GeoPoint tokyoStation = GeoPoint(35.681236, 139.767125);

// Center of the geo query.
final GeoFirePoint center = GeoFirePoint(tokyoStation);

// Detection range from the center point.
const double radiusInKm = 50;

// Field name of Cloud Firestore documents where the geohash is saved.
const String field = 'geo';
```

--------------------------------

### Add geoflutterfire_plus Dependency

Source: https://pub.dev/packages/geoflutterfire_plus/install

Use this command to add the geoflutterfire_plus package to your Flutter project. This command automatically updates your pubspec.yaml file.

```bash
$ flutter pub add geoflutterfire_plus
```

--------------------------------

### Perform Type-Safe Geo-Query with Converter

Source: https://pub.dev/packages/geoflutterfire_plus

Execute a geo-query using the typed collection reference, receiving streams of typed Location document snapshots.

```dart
// Streamed typed document snapshots of geo query under given conditions.
final Stream<List<DocumentSnapshot<Location>>> stream =
    GeoCollectionReference<Location>(typedCollectionReference).subscribeWithin(
  center: center,
  radiusInKm: radiusInKm,
  field: field,
  geopointFrom: geopointFrom,
);
```

--------------------------------

### Define Typed Collection Reference with Converter

Source: https://pub.dev/packages/geoflutterfire_plus

Configure a Firestore collection reference to use a converter for automatic serialization and deserialization of Location objects.

```dart
/// Reference to the collection where the location data is stored.
final typedCollectionReference = 
    FirebaseFirestore.instance.collection('locations').withConverter<Location>(
          fromFirestore: (ds, _) => Location.fromDocumentSnapshot(ds),
          toFirestore: (obj, _) => obj.toJson(),
        );

// Function to get GeoPoint instance from Location instance.
GeoPoint geopointFrom: (Location location) => location.geo.geopoint;
```

--------------------------------

### Geo Query Condition Class

Source: https://pub.dev/packages/geoflutterfire_plus/example

A simple class to hold the parameters for a geographic query, including the radius and the camera position.

```dart
class _GeoQueryCondition {
  _GeoQueryCondition({
    required this.radiusInKm,
    required this.cameraPosition,
  });

  final double radiusInKm;
  final CameraPosition cameraPosition;
}
```

--------------------------------

### Define a custom query condition

Source: https://pub.dev/packages/geoflutterfire_plus

Define a function that takes a Query object and returns a modified Query with additional filters.

```dart
// Custom query condition.
Query<Location> queryBuilder(Query<Location> query) =>
    query.where('isVisible', isEqualTo: true);
```

--------------------------------

### Apply custom query to a geo-query

Source: https://pub.dev/packages/geoflutterfire_plus

Pass the defined queryBuilder function to the subscribeWithin method to filter results.

```dart
// Streamed typed document snapshots of geo query under custom query conditions.
final Stream<List<DocumentSnapshot<Map<String, dynamic>>>> stream =
    GeoCollectionReference<Map<String, dynamic>>(typedCollectionReference)
        .subscribeWithin(
  center: center,
  radiusInKm: radiusInKm,
  field: field,
  geopointFrom: geopointFrom,
  // Specify queryBuilder parameter here.
  queryBuilder: queryBuilder,
);
```

--------------------------------

### Add Location FloatingActionButton

Source: https://pub.dev/packages/geoflutterfire_plus/example

A floating action button that, when pressed, displays a dialog to add a new location. If the button is pressed without a specific location context, it opens a dialog to add a new entry.

```dart
FloatingActionButton(
        onPressed: () => showDialog<void>(
          context: context,
          builder: (context) => const AddLocationDialog(),
        ),
        child: const Icon(Icons.add),
      )
```

--------------------------------

### Define Location and Geo Entity Classes

Source: https://pub.dev/packages/geoflutterfire_plus

Create Dart classes for your Firestore documents, including a nested 'geo' object, to enable type-safe data handling.

```dart
/// An entity of Cloud Firestore location document.
class Location {
  Location({
    required this.geo,
    required this.name,
    required this.isVisible,
  });

  factory Location.fromJson(Map<String, dynamic> json) => Location(
        geo: Geo.fromJson(json['geo'] as Map<String, dynamic>),
        name: json['name'] as String,
        isVisible: (json['isVisible'] ?? false) as bool,
      );

  factory Location.fromDocumentSnapshot(DocumentSnapshot documentSnapshot) =>
      Location.fromJson(documentSnapshot.data()! as Map<String, dynamic>);

  final Geo geo;
  final String name;
  final bool isVisible;

  Map<String, dynamic> toJson() => <String, dynamic>{
        'geo': geo.toJson(),
        'name': name,
        'isVisible': isVisible,
      };
}

/// An entity of `geo` field of Cloud Firestore location document.
class Geo {
  Geo({
    required this.geohash,
    required this.geopoint,
  });

  factory Geo.fromJson(Map<String, dynamic> json) => Geo(
        geohash: json['geohash'] as String,
        geopoint: json['geopoint'] as GeoPoint,
      );

  final String geohash;
  final GeoPoint geopoint;

  Map<String, dynamic> toJson() => <String, dynamic>{
        'geohash': geohash,
        'geopoint': geopoint,
      };
}
```

--------------------------------

### Save geo data to Firestore

Source: https://pub.dev/packages/geoflutterfire_plus

Methods for adding or updating geographic data in Cloud Firestore collections.

```dart
// Adds new documents to locations collection.
GeoCollectionReference<Map<String, dynamic>>(
  FirebaseFirestore.instance.collection('locations'),
).add(<String, dynamic>{
  'geo': geoFirePoint.data,
  'name': name,
  'isVisible': true,
});
```

```dart
// Adds new documents to locations collection.
FirebaseFirestore.instance.collection('locations').add(
  <String, dynamic>{
    'geo': geoFirePoint.data,
    'name': 'Tokyo Station',
    'isVisible': true,
  },
);
```

```dart
// Sets a new document by giving geoFirePoint.data to 'geo' field.
GeoCollectionReference(FirebaseFirestore.instance.collection('locations'))
    .set(
  id: 'your-document-id',
  data: {
    'geo': geoFirePoint.data,
    'foo': 'foo',
    'bar': 'bar',
  },
  options: SetOptions(merge: true),
);

// Updates an existing document's 'geo' field by giving GeoPoint instance.
GeoCollectionReference(FirebaseFirestore.instance.collection('locations'))
    .updatePoint(
  id: 'your-document-id',
  field: 'geo',
  geopoint: GeoPoint(35.681236, 139.767125),
);
```

--------------------------------

### Firestore Collection Reference

Source: https://pub.dev/packages/geoflutterfire_plus/example

Defines a reference to the 'locations' collection in Firestore. This can be used with or without a Firestore converter for type safety.

```dart
final _collectionReference = FirebaseFirestore.instance.collection('locations');
```

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