feat: add possibility to track location

Close #117

src/main/java/com/flowingcode/vaadin/addons/googlemaps/GoogleMap.java

@@ -609,6 +609,61 @@ public Registration addGeolocationErrorEventListener(
       ComponentEventListener<GeolocationErrorEvent> listener) {
     return addListener(GeolocationErrorEvent.class, listener);
   }
+
+  /**
+   * Activates tracking current location on map.
+   * 
+   * <p>Uses <a href=
+   * "https://developer.mozilla.org/en-US/docs/Web/API/Geolocation/watchPosition">geolocation#watchPosition</a>
+   * method to track current position.</p>
+   * 
+   * <p>Geolocation requires that the user gives consent to location sharing when prompted by the
+   * browser.</p>
+   */
+  public void trackLocation() {
+    getElement().executeJs("return geolocation.trackLocation($0)", this).then(Integer.class,
+        trackLocationId -> {
+          ComponentUtil.fireEvent(this,
+              new LocationTrackingActivatedEvent(this, false, trackLocationId));
+        });
+  }
+
+  /** Event that is fired when activating location tracking. */
+  public class LocationTrackingActivatedEvent extends ComponentEvent<GoogleMap> {
+
+    private Integer trackLocationId;
+
+    public LocationTrackingActivatedEvent(GoogleMap source, boolean fromClient,
+        Integer trackLocationId) {
+      super(source, fromClient);
+      this.trackLocationId = trackLocationId;
+    }
+
+    public Integer getTrackLocationId() {
+      return trackLocationId;
+    }
+  }
+
+  /**
+   * Adds a LocationTrackingActivatedEvent listener. The listener is called when setting activating
+   * tracking location.
+   *
+   * @param listener a listener for a LocationTrackingActivatedEvent
+   * @return a handle for the listener
+   */
+  public Registration addLocationTrackingActivatedEventListener(
+      ComponentEventListener<LocationTrackingActivatedEvent> listener) {
+    return addListener(LocationTrackingActivatedEvent.class, listener);
+  }
+
+  /**
+   * Stops location tracking.
+   * 
+   * @param trackLocationId the id of the current activated location tracking
+   */
+  public void stopTrackLocation(Integer trackLocationId) {
+    getElement().executeJs("geolocation.clearTracking($0)", trackLocationId);
+  }
 
   /**
    * Returns a {@link CompletableFuture} containing the map current {@link LatLonBounds bounds}.

src/main/resources/META-INF/resources/frontend/googlemaps/geolocation.js

@@ -20,20 +20,46 @@
 window.geolocation = {
 
 	get: function(map) {
-    // if browser supports geolocation, return current location
-    if(navigator.geolocation) {
+		// if browser supports geolocation, return current location
+		if (navigator.geolocation) {
 
-      navigator.geolocation.getCurrentPosition(
-      position => {
-        map.$server.handleGeolocation(position.coords.latitude, position.coords.longitude);
-      },
-      () => {
-        map.$server.handleGeolocationError(true);
-      });      
-
-    } else { // browser doesn't support geolocation
-      map.$server.handleGeolocationError(false);
-    }
-  }
+			navigator.geolocation.getCurrentPosition(
+				position => {
+					map.$server.handleGeolocation(position.coords.latitude, position.coords.longitude);
+				}, 
+				() => {
+					this._handleGeolocationError(true, map);
+				}
+			);
 
+		} else { // browser doesn't support geolocation
+			this._handleGeolocationError(false, map);
+		}
+	},
+
+	trackLocation: function(map) {
+		let trackLocationId;
+		if (navigator.geolocation) {
+
+			trackLocationId = navigator.geolocation.watchPosition(
+				position => {
+					map.$server.handleGeolocation(position.coords.latitude, position.coords.longitude);
+				}, 
+				() => {
+					this._handleGeolocationError(true, map);
+				}
+			);
+		} else { // browser doesn't support geolocation
+			this._handleGeolocationError(false, map);
+		}
+		return trackLocationId;
+	},
+
+	clearTracking: function(id) {
+		navigator.geolocation.clearWatch(id);
+	},
+
+	_handleGeolocationError(error, map){
+		map.$server.handleGeolocationError(error);
+	}
 }

src/test/java/com/flowingcode/vaadin/addons/googlemaps/GooglemapsDemoView.java

@@ -46,6 +46,7 @@ public GooglemapsDemoView() {
     addDemo(ClusteringWithCustomRendererDemo.class);
     addDemo(PolylinesDemo.class);
     addDemo(CustomizedMarkerIconsDemo.class);
+    addDemo(TrackLocationDemo.class);
     setSizeFull();
   }
 }

src/test/java/com/flowingcode/vaadin/addons/googlemaps/TrackLocationDemo.java

@@ -0,0 +1,76 @@
+/*-
+ * #%L
+ * Google Maps Addon
+ * %%
+ * Copyright (C) 2020 - 2024 Flowing Code
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+
+package com.flowingcode.vaadin.addons.googlemaps;
+
+import com.flowingcode.vaadin.addons.demo.DemoSource;
+import com.flowingcode.vaadin.addons.googlemaps.GoogleMap.MapType;
+import com.vaadin.flow.component.button.Button;
+import com.vaadin.flow.component.notification.Notification;
+import com.vaadin.flow.router.PageTitle;
+import com.vaadin.flow.router.Route;
+
+@PageTitle("Track Location Demo")
+@DemoSource
+@Route(value = "googlemaps/tracklocation", layout = GooglemapsDemoView.class)
+@SuppressWarnings("serial")
+public class TrackLocationDemo extends AbstractGoogleMapsDemo {
+
+  private Integer trackLocationId = null;
+
+  @Override
+  protected void createGoogleMapsDemo(String apiKey) {
+    GoogleMap gmaps = new GoogleMap(apiKey, null, null);
+    gmaps.setMapType(MapType.ROADMAP);
+    gmaps.setSizeFull();
+    gmaps.setZoom(15);
+    add(gmaps);
+
+    // create button to activate location tracking
+    Button startLocationTrackingButton =
+        new Button("Start tracking my location", e -> gmaps.trackLocation());
+    // create button to stop location tracking
+    Button stopLocationTrackingButton =
+        new Button("Stop tracking my location", e -> gmaps.stopTrackLocation(trackLocationId));
+    add(startLocationTrackingButton, stopLocationTrackingButton);
+
+    // create marker to track location
+    GoogleMapMarker locationMarker = new GoogleMapMarker();
+    locationMarker.setCaption("You're here");
+    locationMarker.setDraggable(false);
+    gmaps.addMarker(locationMarker);
+
+    // add listener to obtain id when track location is activated
+    gmaps.addLocationTrackingActivatedEventListener(ev -> {
+      trackLocationId = ev.getTrackLocationId();
+    });
+
+    // add listener to know when location was updated and update location marker position
+    gmaps.addCurrentLocationEventListener(e -> {
+      locationMarker.setPosition(e.getSource().getCenter());
+    });
+
+    // add listener to capture geolocation error
+    gmaps.addGeolocationErrorEventListener(e -> {
+      if (!e.isBrowserHasGeolocationSupport())
+        Notification.show("Your browser doesn't support geolocation.");
+    });
+  }
+}