Merge pull request #83 from Esri/cs/1553_location_history_update

changanxian · web-flow · commit b604e60fe3c3 · 2024-07-23T13:48:05.000-07:00
"Show Device Location History" sample updated
diff --git a/lib/samples/show_device_location_history/README.md b/lib/samples/show_device_location_history/README.md
@@ -0,0 +1,42 @@
+# Show device location history
+
+Display your device's location history on the map.
+
+![Image of show device location history](show_device_location_history.png)
+
+## Use case
+
+You can track device location history and display it as lines and points on the map. The history can be used to visualize how the user moved through the world, to retrace their steps, or to create new feature geometry. An unmapped trail, for example, could be added to the map using this technique.
+
+## How to use the sample
+
+Tap 'Start Tracking' to start tracking your location, which will appear as points on the map. A line will connect the points for easier visualization. Tap 'Stop Tracking' to stop updating the location history. This sample uses a simulated data source to allow the sample to be useful on desktop/non-mobile devices. To track a user's real position, use the `LocationDataSource` instead.
+
+## How it works
+
+1. Create a graphics overlay to show each point and another graphics overlay for displaying the route line.
+2. Create a `SimulatedLocationDataSource` and initialize it with a polyline. Start the `SimulatedLocationDataSource` to begin receiving location updates.
+ - NOTE: To track a user's real position, use `LocationDataSource` instead.
+3. Subscribe to the `onLocationChanged` event to handle location updates.
+4. Every time the location updates, store that location, display a point on the map, and recreate the route line.
+
+## Relevant API
+
+* LocationDataSource
+* LocationDisplay
+* LocationDisplayAutoPanMode
+* PolylineBuilder
+* SimpleLineSymbol
+* SimpleMarkerSymbol
+* SimpleRenderer
+* SimulatedLocationDataSource
+* Graphic
+* GraphicsOverlay
+
+## About the data
+
+A custom set of points is used to create a `Polyline` and initialize a `SimulatedLocationDataSource`. This simulated location data source enables easier testing and allows the sample to be used on devices without an actively updating GPS signal.
+
+## Tags
+
+bread crumb, breadcrumb, GPS, history, movement, navigation, real-time, trace, track, trail
diff --git a/lib/samples/show_device_location_history/README.metadata.json b/lib/samples/show_device_location_history/README.metadata.json
@@ -2,10 +2,46 @@
     "category": "Maps",
     "description": "Display your device's location history on the map.",
     "ignore": false,
-    "images": [],
-    "keywords": [],
+    "images": [
+        "show_device_location_history.png"
+    ],
+    "keywords": [
+        "GPS",
+        "bread crumb",
+        "breadcrumb",
+        "history",
+        "movement",
+        "navigation",
+        "real-time",
+        "trace",
+        "track",
+        "trail",
+        "Graphic",
+        "GraphicsOverlay",
+        "LocationDataSource",
+        "LocationDisplay",
+        "LocationDisplayAutoPanMode",
+        "PolylineBuilder",
+        "SimpleLineSymbol",
+        "SimpleMarkerSymbol",
+        "SimpleRenderer",
+        "SimulatedLocationDataSource"
+    ],
     "redirect_from": [],
-    "relevant_apis": [],
-    "snippets": [],
+    "relevant_apis": [
+        "Graphic",
+        "GraphicsOverlay",
+        "LocationDataSource",
+        "LocationDisplay",
+        "LocationDisplayAutoPanMode",
+        "PolylineBuilder",
+        "SimpleLineSymbol",
+        "SimpleMarkerSymbol",
+        "SimpleRenderer",
+        "SimulatedLocationDataSource"
+    ],
+    "snippets": [
+        "show_device_location_history_sample.dart"
+    ],
     "title": "Show device location history"
 }
diff --git a/lib/samples/show_device_location_history/show_device_location_history.png b/lib/samples/show_device_location_history/show_device_location_history.png
diff --git a/lib/samples/show_device_location_history/show_device_location_history_sample.dart b/lib/samples/show_device_location_history/show_device_location_history_sample.dart
@@ -32,20 +32,31 @@ class ShowDeviceLocationHistorySample extends StatefulWidget {
 
 class _ShowDeviceLocationHistorySampleState
     extends State<ShowDeviceLocationHistorySample> with SampleStateSupport {
+  // Create a controller for the map view.
   final _mapViewController = ArcGISMapView.createController();
-  double _latitude = 0.0;
-  double _longitude = 0.0;
-  double _heading = 0.0;
+  // A location data source to simulate location updates.
   final _locationDataSource = SimulatedLocationDataSource();
-  StreamSubscription? _statusSubscription;
+  // Subscription to listen for location changes.
   StreamSubscription? _locationSubscription;
-  ArcGISException? _ldsException;
+  // A GraphicsOverlay to display the location history polyline.
+  final _locationHistoryLineOverlay = GraphicsOverlay();
+  // A GraphicsOverlay to display the location history points.
+  final _locationHistoryPointOverlay = GraphicsOverlay();
+  // A PolylineBuilder to build the location history polyline.
+  final _polylineBuilder = PolylineBuilder.fromSpatialReference(
+    SpatialReference.wgs84,
+  );
+  // A flag for when the map view is ready and controls can be used.
+  var _ready = false;
+  // A flag for toggling location tracking.
+  var _enableTracking = false;
 
   @override
   void dispose() {
     _locationDataSource.stop();
     _locationSubscription?.cancel();
-    _statusSubscription?.cancel();
+    _locationHistoryLineOverlay.graphics.clear();
+    _locationHistoryPointOverlay.graphics.clear();
 
     super.dispose();
   }
@@ -54,80 +65,59 @@ class _ShowDeviceLocationHistorySampleState
   Widget build(BuildContext context) {
     return Scaffold(
       body: SafeArea(
-        child: Column(
-          crossAxisAlignment: CrossAxisAlignment.center,
+        top: false,
+        child: Stack(
           children: [
-            Expanded(
-              child: Stack(
-                alignment: Alignment.bottomRight,
-                children: [
-                  ArcGISMapView(
+            Column(
+              children: [
+                Expanded(
+                  // Add a map view to the widget tree and set a controller.
+                  child: ArcGISMapView(
                     controllerProvider: () => _mapViewController,
                     onMapViewReady: onMapViewReady,
                   ),
-                  Positioned(
-                    bottom: 60.0,
-                    right: 10.0,
-                    child: Container(
-                      color: Colors.white,
-                      padding: const EdgeInsets.all(5.0),
-                      child: Column(
-                        mainAxisAlignment: MainAxisAlignment.center,
-                        crossAxisAlignment: CrossAxisAlignment.start,
-                        children: [
-                          const Text(
-                            'Device Location:',
-                            style: TextStyle(fontWeight: FontWeight.bold),
-                          ),
-                          Text('Latitude: $_latitude'),
-                          Text('Longitude: $_longitude'),
-                          Text('Heading: $_heading')
-                        ],
-                      ),
-                    ),
-                  )
-                ],
-              ),
-            ),
-            SizedBox(
-              height: 90,
-              width: double.infinity,
-              child: Column(
-                children: [
-                  const Text('Location Data Source'),
-                  Visibility(
-                    visible: _ldsException == null,
-                    child: ElevatedButton(
-                      child: Text(_locationDataSource.status ==
-                              LocationDataSourceStatus.started
-                          ? 'Stop'
-                          : 'Start'),
+                ),
+                Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+                  children: [
+                    // A button to enable or disable location tracking.
+                    ElevatedButton(
                       onPressed: () {
-                        if (_locationDataSource.status ==
-                            LocationDataSourceStatus.started) {
-                          _mapViewController.locationDisplay.stop();
-                        } else {
-                          _mapViewController.locationDisplay.start();
-                        }
+                        setState(() {
+                          _enableTracking = !_enableTracking;
+                        });
                       },
+                      child: Text(
+                        _enableTracking ? 'Stop Tracking' : 'Start Tracking',
+                      ),
                     ),
+                  ],
+                ),
+              ],
+            ),
+            // Display a progress indicator and prevent interaction until state is ready.
+            Visibility(
+              visible: !_ready,
+              child: SizedBox.expand(
+                child: Container(
+                  color: Colors.white30,
+                  child: const Center(
+                    child: CircularProgressIndicator(),
                   ),
-                  Visibility(
-                    visible: _ldsException != null,
-                    child: Text('Exception: ${_ldsException?.message}'),
-                  ),
-                ],
+                ),
               ),
-            )
+            ),
           ],
         ),
       ),
     );
   }
 
+  // The method is called when the map view is ready to be used.
   void onMapViewReady() async {
-    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISImageryStandard);
-
+    // Create a map with the ArcGIS Navigation basemap style.
+    final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISNavigation);
+    // Set the initial viewpoint.
     map.initialViewpoint = Viewpoint.fromCenter(
       ArcGISPoint(
         x: -110.8258,
@@ -136,43 +126,95 @@ class _ShowDeviceLocationHistorySampleState
       ),
       scale: 2e4,
     );
-
+    // Add the map to the map view controller.
     _mapViewController.arcGISMap = map;
-    await _initLocationDisplay();
+    // Add the graphics overlays to the map view.
+    _mapViewController.graphicsOverlays.addAll([
+      _locationHistoryLineOverlay,
+      _locationHistoryPointOverlay,
+    ]);
+    // Set the renderers for the graphics overlays.
+    _locationHistoryLineOverlay.renderer = SimpleRenderer(
+      symbol: SimpleLineSymbol(
+        color: Colors.red[100]!,
+        width: 2.0,
+      ),
+    );
+    _locationHistoryPointOverlay.renderer = SimpleRenderer(
+      symbol: SimpleMarkerSymbol(
+        color: Colors.red,
+        size: 10.0,
+      ),
+    );
+    // Wait for the map to be displayed before starting the location display.
+    _mapViewController.onDrawStatusChanged.listen((status) async {
+      if (status == DrawStatus.completed &&
+          _locationDataSource.status == LocationDataSourceStatus.stopped) {
+        await _initLocationDisplay();
+      }
+    });
+    // Set the ready state variable to true to enable the sample UI.
+    setState(() => _ready = true);
   }
 
+  // Initialize the location display with the location data source.
   Future<void> _initLocationDisplay() async {
     final locationDisplay = _mapViewController.locationDisplay;
     locationDisplay.dataSource = _locationDataSource;
     locationDisplay.autoPanMode = LocationDisplayAutoPanMode.recenter;
     locationDisplay.useCourseSymbolOnMovement = true;
-    await _initLocationDataSource();
+    await _startLocationDataSource();
   }
 
-  Future<void> _initLocationDataSource() async {
+  // Start the location data source and listen for location changes.
+  Future<void> _startLocationDataSource() async {
     final routeLineJson =
         await rootBundle.loadString('assets/SimulatedRoute.json');
     final routeLine = Geometry.fromJsonString(routeLineJson) as Polyline;
     _locationDataSource.setLocationsWithPolyline(routeLine);
-    _statusSubscription = _locationDataSource.onStatusChanged.listen((_) {
-      // Redraw the screen when the LDS status changes
-      setState(() {});
-    });
 
+    // Start the location data source.
     try {
       await _locationDataSource.start();
-      _locationSubscription = _locationDataSource.onLocationChanged
-          .listen(_handleLdsLocationChange);
     } on ArcGISException catch (e) {
-      setState(() => _ldsException = e);
+      if (mounted) {
+        showDialog(
+          context: context,
+          builder: (_) => AlertDialog(
+            content: Text(
+              e.message,
+            ),
+          ),
+        );
+      }
+    }
+
+    // Listen for location changes.
+    if (_locationDataSource.status == LocationDataSourceStatus.started) {
+      _locationSubscription = _locationDataSource.onLocationChanged.listen(
+        _handleLdsLocationChange,
+      );
     }
   }
 
+  // Handle location changes from the location data source.
   void _handleLdsLocationChange(ArcGISLocation location) {
-    setState(() {
-      _latitude = location.position.y;
-      _longitude = location.position.x;
-      _heading = location.course;
-    });
+    if (!_enableTracking) return;
+    // Add the location to the location history as a graphic point.
+    final point = location.position;
+    _locationHistoryPointOverlay.graphics.add(
+      Graphic(
+        geometry: point,
+      ),
+    );
+    // Add the location to the location history as a polyline.
+    _polylineBuilder.addPoint(point);
+    // Visualize the location history polyline on the map.
+    _locationHistoryLineOverlay.graphics.clear();
+    _locationHistoryLineOverlay.graphics.add(
+      Graphic(
+        geometry: _polylineBuilder.toGeometry() as Polyline,
+      ),
+    );
   }
 }
