Find the service area within a network from a given point.
Use case
A service area shows locations that can be reached from a facility based off a certain impedance, such as travel time or distance. Barriers can increase impedance by either adding to the time it takes to pass through the barrier or by altogether preventing passage.
You might calculate the region around a hospital in which ambulances can service in 30 minutes or less.
How to use the sample
In order to find any service areas at least one facility needs to be added to the map view.
- To add a facility, tap the facility button, then tap anywhere on the map.
- To add a barrier, tap the barrier button, and tap multiple locations on the map.
- To show service areas around facilities that were added, tap the service areas button.
- The reset button clears all graphics and resets the service area task.
How it works
- Create a new
ServiceAreaTaskfrom a network service. - Create default
ServiceAreaParametersfrom the service area task. - Set the parameters to return polygons (true) to return all service areas.
- Add a
ServiceAreaFacilityto the parameters. - Get the
ServiceAreaResultby solving the service area task using the parameters. - Get any
ServiceAreaPolygonsthat were returned,serviceAreaResult.getResultPolygons(facilityIndex). - Display the service area polygons as graphics in a
GraphicsOverlayon theArcGISMapView.
Relevant API
- PolylineBarrier
- ServiceAreaFacility
- ServiceAreaParameters
- ServiceAreaPolygon
- ServiceAreaResult
- ServiceAreaTask
Tags
barriers, facilities, impedance, logistics, routing
Sample Code
show_service_area.dart
//
// Copyright 2024 Esri
//
// 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
//
// https://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.
//
import 'package:arcgis_maps/arcgis_maps.dart';
import 'package:flutter/material.dart';
import '../../utils/sample_state_support.dart';
class ShowServiceArea extends StatefulWidget {
const ShowServiceArea({super.key});
@override
State<ShowServiceArea> createState() => _ShowServiceAreaState();
}
class _ShowServiceAreaState extends State<ShowServiceArea>
with SampleStateSupport {
// Create a map view controller.
final _mapViewController = ArcGISMapView.createController();
// Create graphics overlays for displaying facilities and barriers.
final _facilityGraphicsOverlay = GraphicsOverlay();
final _barrierGraphicsOverlay = GraphicsOverlay();
// Create a graphics overlay for displays service area results and a list of symbols applied for each impedence cutoff added to the service area parameters.
final _serviceAreaGraphicsOverlay = GraphicsOverlay();
final _serviceAreaSymbols = [
SimpleFillSymbol(
color: Colors.yellowAccent.withOpacity(0.4),
outline: SimpleLineSymbol(color: Colors.yellow.withOpacity(0.8)),
),
SimpleFillSymbol(
color: Colors.orangeAccent.withOpacity(0.4),
outline: SimpleLineSymbol(color: Colors.orange.withOpacity(0.8)),
),
SimpleFillSymbol(
color: Colors.greenAccent.withOpacity(0.4),
outline: SimpleLineSymbol(color: Colors.green.withOpacity(0.8)),
),
];
// Create a service area task used to find service areas around a facility.
final _serviceAreaTask = ServiceAreaTask.withUri(
Uri.parse(
'https://route-api.arcgis.com/arcgis/rest/services/World/ServiceAreas/NAServer/ServiceArea_World',
),
);
late final ServiceAreaParameters _serviceAreaParameters;
// A state variable for controlling the segmented button selection.
var _segmentedButtonSelection = Selection.facility;
// A flag for when the map view is ready and controls can be used.
var _ready = false;
// A flag for when the service area task is in progress.
var _taskInProgress = false;
@override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
top: false,
child: Stack(
children: [
Column(
children: [
Expanded(
// Add a map view to the widget tree and set a controller.
child: ArcGISMapView(
controllerProvider: () => _mapViewController,
onMapViewReady: onMapViewReady,
onTap: onTap,
),
),
SizedBox(
height: 60,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
// Create segmented buttons for toggling adding a facility or barrier to the map.
SegmentedButton(
segments: const [
ButtonSegment(
value: Selection.facility,
label: Text('Facility'),
),
ButtonSegment(
value: Selection.barrier,
label: Text('Barrier'),
),
],
selected: {_segmentedButtonSelection},
onSelectionChanged: (newSelection) {
setState(() {
_segmentedButtonSelection = newSelection.first;
});
},
multiSelectionEnabled: false,
showSelectedIcon: false,
),
// Create buttons for calculating the service area and resetting.
ElevatedButton(
onPressed: solveServiceArea,
child: const Text('Service Areas'),
),
ElevatedButton(
onPressed: resetServiceArea,
child: const Text('Reset'),
),
],
),
),
],
),
// Display a progress indicator when the ready flag is false - this will indicate the map is loading or the service area task is in progress.
Visibility(
visible: !_ready || _taskInProgress,
child: SizedBox.expand(
child: Container(
color: Colors.white30,
child: const Center(child: CircularProgressIndicator()),
),
),
),
],
),
),
);
}
void onMapViewReady() async {
// Create a map with the light gray basemap style and an initial viewpoint.
final map = ArcGISMap.withBasemapStyle(BasemapStyle.arcGISLightGray)
..initialViewpoint = Viewpoint.withLatLongScale(
latitude: 32.73,
longitude: -117.16,
scale: 25000,
);
// Set the map to the map view.
_mapViewController.arcGISMap = map;
// Apply a renderer to the barrier graphics overlay.
_barrierGraphicsOverlay.renderer = SimpleRenderer(
symbol: SimpleFillSymbol(
style: SimpleFillSymbolStyle.diagonalCross,
color: Colors.red,
),
);
// Apply a renderer to the facility graphics overlay.
_facilityGraphicsOverlay.renderer = SimpleRenderer(
symbol: PictureMarkerSymbol.withUri(
Uri.parse(
'https://static.arcgis.com/images/Symbols/SafetyHealth/Hospital.png',
),
),
);
// Add the graphics overlays to the map view.
_mapViewController.graphicsOverlays.addAll([
_serviceAreaGraphicsOverlay,
_facilityGraphicsOverlay,
_barrierGraphicsOverlay,
]);
try {
// Create default service area parameters for using to solve a service area task.
_serviceAreaParameters = await _serviceAreaTask.createDefaultParameters();
// Note: returnPolygons defaults to true to return all service areas.
// Set the overlap behavior when there are results for multiple facilities.
_serviceAreaParameters.geometryAtOverlap =
ServiceAreaOverlapGeometry.dissolve;
// Customize impedance cutoffs for facilities (drive time minutes).
// Note: the defaults are initially set as 5, 10 and 15.
_serviceAreaParameters.defaultImpedanceCutoffs.clear();
_serviceAreaParameters.defaultImpedanceCutoffs.addAll([3, 8, 12]);
} on Exception catch (e) {
if (mounted) {
showDialog(
context: context,
builder: (context) => AlertDialog(
content: Text('Error creating service area parameters:\n $e'),
),
);
}
}
// Toggle the _ready flag to enable the UI.
setState(() => _ready = true);
}
void onTap(Offset screenPoint) {
// Capture the tapped point and convert it to a map point.
final mapTapPoint =
_mapViewController.screenToLocation(screen: screenPoint);
if (mapTapPoint == null) return;
// Add a facility or barrier to the map depending on the current toggle button selection.
if (_segmentedButtonSelection == Selection.facility) {
_facilityGraphicsOverlay.graphics.add(Graphic(geometry: mapTapPoint));
} else {
// Create a buffer around the tapped point to create a barrier.
final barrierGeometry =
GeometryEngine.buffer(geometry: mapTapPoint, distance: 200);
_barrierGraphicsOverlay.graphics.add(Graphic(geometry: barrierGeometry));
}
}
void solveServiceArea() async {
// Require at least 1 facility to perform a service area calculation.
if (_facilityGraphicsOverlay.graphics.isNotEmpty) {
// Disable the UI while the service area is calculated.
setState(() => _taskInProgress = true);
// Clear previous calculations.
_serviceAreaGraphicsOverlay.graphics.clear();
// For each graphic in the facilities graphics overlay, add a facility to the parameters.
final facilities = _facilityGraphicsOverlay.graphics
.map(
(graphic) => ServiceAreaFacility(graphic.geometry as ArcGISPoint),
)
.toList();
_serviceAreaParameters.setFacilities(facilities);
// For each graphic in the barriers graphics overlay, add a polygon barrier to the parameters.
final barriers = _barrierGraphicsOverlay.graphics
.map(
(graphic) => PolygonBarrier(graphic.geometry as Polygon),
)
.toList();
_serviceAreaParameters.setPolygonBarriers(barriers);
// Solve the service area using the parameters.
final serviceAreaResult = await _serviceAreaTask.solveServiceArea(
_serviceAreaParameters,
);
// Display service area polygons for each facility - since the service area parameters have
// geometryAtOverlap set to dissolve and the impedence cutoff values are the same across facilities,
// we only need to draw the joined polygons for one of the facilities.
final serviceAreaPolygons =
serviceAreaResult.getResultPolygons(facilityIndex: 0);
for (var i = 0; i < serviceAreaPolygons.length; i++) {
_serviceAreaGraphicsOverlay.graphics.add(
Graphic(
geometry: serviceAreaPolygons[i].geometry,
symbol: _serviceAreaSymbols[i],
),
);
}
// Re-enable the UI once the service area task is finished.
setState(() => _taskInProgress = false);
} else {
showDialog(
context: context,
builder: (context) => AlertDialog(
content: const Text(
'At least 1 facility is required to perform a service area calculation.',
),
actions: [
TextButton(
onPressed: () => Navigator.pop(context, 'OK'),
child: const Text('OK'),
),
],
),
);
}
}
void resetServiceArea() {
// Clear the facilities and polygon barriers from the service area parameters.
_serviceAreaParameters.clearFacilities();
_serviceAreaParameters.clearPolygonBarriers();
// Clear all the graphics from the map.
_mapViewController.graphicsOverlays
.map((overlay) => overlay.graphics.clear())
.toList();
}
}
enum Selection { facility, barrier }