Added map move event, added zoom & bounds attributes

lib/src/core/google_map.dart

@@ -7,6 +7,7 @@ import 'package:flutter/foundation.dart';
 
 import 'package:google_directions_api/google_directions_api.dart'
     show GeoCoord, DirectionsService;
+import 'package:google_maps_flutter/google_maps_flutter.dart' as gmap;
 
 import 'map_items.dart';
 import 'map_operations.dart';
@@ -27,6 +28,7 @@ class GoogleMap extends StatefulWidget {
     this.markers,
     this.onTap,
     this.onLongPress,
+    this.onMapMove,
     this.interactive = true,
     this.initialZoom = _zoom,
     this.mapType = MapType.roadmap,
@@ -85,6 +87,8 @@ class GoogleMap extends StatefulWidget {
   /// For `web` this will be called when `right mouse clicked`.
   final ValueChanged<GeoCoord> onLongPress;
 
+  final ValueChanged<gmap.CameraPosition> onMapMove;
+
   /// Set of mobile map preferences.
   final MobileMapPreferences mobilePreferences;
 
@@ -117,4 +121,4 @@ abstract class GoogleMapStateBase extends State<GoogleMap>
       icon.endsWith('/marker_a.png') || icon.endsWith('/marker_b.png')
           ? 'packages/flutter_google_maps/'
           : '';
-}
+}

lib/src/core/google_map.state.dart

@@ -13,6 +13,7 @@ import 'map_items.dart';
 import 'google_map.dart';
 
 class GoogleMapState extends GoogleMapStateBase {
+
   @override
   void moveCameraBounds(
     GeoCoordBounds newBounds, {
@@ -42,6 +43,10 @@ class GoogleMapState extends GoogleMapStateBase {
   @override
   FutureOr<GeoCoord> get center => throw UnimplementedError();
 
+  FutureOr<double> get zoom => throw UnimplementedError();
+
+  FutureOr<GeoCoordBounds> get bounds => throw UnimplementedError();
+
   @override
   void changeMapStyle(
     String mapStyle, {

lib/src/core/map_operations.dart

@@ -68,6 +68,12 @@ abstract class MapOperations implements MapMarkers, MapDirections, MapPolygons {
 
   /// Gets center coordinates of the map.
   FutureOr<GeoCoord> get center;
+
+  /// Gets zoom coordinates of the map.
+  FutureOr<double> get zoom;
+
+  /// Gets zoom coordinates of the map.
+  FutureOr<GeoCoordBounds> get bounds;
 
   /// Sets the styling of the base map.
   ///

lib/src/mobile/google_map.state.dart

@@ -140,6 +140,11 @@ class GoogleMapState extends gmap.GoogleMapStateBase {
   FutureOr<GeoCoord> get center async =>
       (await _controller?.getVisibleRegion())?.toGeoCoordBounds()?.center;
 
+  FutureOr<double> get zoom async =>
+      (await _controller?.getZoomLevel());
+
+  FutureOr<GeoCoordBounds> get bounds async => (await _controller?.getVisibleRegion()).toGeoCoordBounds();
+
   @override
   void changeMapStyle(
     String mapStyle, {
@@ -504,6 +509,8 @@ class GoogleMapState extends gmap.GoogleMapStateBase {
               onTap: (coords) => widget.onTap?.call(coords?.toGeoCoord()),
               onLongPress: (coords) =>
                   widget.onLongPress?.call(coords?.toGeoCoord()),
+              onCameraMove: (position) => 
+                widget.onMapMove?.call(position),
               onMapCreated: (GoogleMapController controller) {
                 _controller = controller;
                 _controller.setMapStyle(widget.mapStyle);

lib/src/web/google_map.state.dart

@@ -8,6 +8,7 @@ import 'dart:ui' as ui;
 
 import 'package:flutter/widgets.dart';
 import 'package:flutter/scheduler.dart' show SchedulerBinding;
+import 'package:google_maps_flutter/google_maps_flutter.dart' as gmaps;
 
 import 'package:uuid/uuid.dart';
 import 'package:flinq/flinq.dart';
@@ -62,13 +63,13 @@ class GoogleMapState extends GoogleMapStateBase {
 
     _map.center = newBounds.center.toLatLng();
 
-    final zoom = _map.zoom;
+    // final zoom = _map.zoom;
     if (animated == true) {
       _map.panToBounds(newBounds.toLatLngBounds());
     } else {
       _map.fitBounds(newBounds.toLatLngBounds());
     }
-    _map.zoom = zoom;
+    // _map.zoom = zoom;
   }
 
   @override
@@ -115,6 +116,10 @@ class GoogleMapState extends GoogleMapStateBase {
   @override
   FutureOr<GeoCoord> get center => _map.center?.toGeoCoord();
 
+  FutureOr<double> get zoom => _map.zoom.toDouble();
+
+  FutureOr<GeoCoordBounds> get bounds => _map.bounds.toGeoCoordBounds();
+
   @override
   void changeMapStyle(
     String mapStyle, {
@@ -553,6 +558,15 @@ class GoogleMapState extends GoogleMapStateBase {
 
         _map = GMap(elem, _mapOptions);
 
+        _subscriptions.add(_map.onCenterChanged.listen(
+            (event) {
+              gmaps.CameraPosition pos = gmaps.CameraPosition(
+                target: gmaps.LatLng( _map.center.lat,  _map.center.lng), 
+                zoom: _map.zoom.toDouble(), 
+                tilt: _map.tilt,
+              );
+              widget.onMapMove?.call(pos);
+            }));
         _subscriptions.add(_map.onClick.listen(
             (event) => widget.onTap?.call(event?.latLng?.toGeoCoord())));
         _subscriptions.add(_map.onRightclick.listen(