Use an online service to find the address for a tapped point.
Use case
You might use a geocoder to find a customer's delivery address based on the location returned by their device's GPS.
How to use the sample
Tap the map to see the nearest address displayed in a callout.
How it works
- Create a
LocatorTask
object using a URL to a geocoder service. - Set the
GeocodeParameters
for theLocatorTask
and specify the geocoder's attributes. - Get the matching results from the
GeocodeResult
usingLocatorTask.reverseGeocodeAsync
. - Show the results using a
PictureMarkerSymbol
and add the symbol to aGraphic
in theGraphicsOverlay
.
Additional information
This sample uses the World Geocoding Service. For more information, see the Geocoding service help topic on the ArcGIS Developer website.
Relevant API
- GeocodeParameters
- LocatorTask
- ReverseGeocodeParameters
Tags
address, geocode, locate, reverse geocode, search
Sample Code
ReverseGeocode.cs
// Copyright 2019 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: 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.
using ArcGISRuntime;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.Tasks.Geocoding;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using UIKit;
namespace ArcGISRuntimeXamarin.Samples.ReverseGeocode
{
[Register("ReverseGeocode")]
[ArcGISRuntime.Samples.Shared.Attributes.Sample(
name: "Reverse geocode",
category: "Search",
description: "Use an online service to find the address for a tapped point.",
instructions: "Tap the map to see the nearest address displayed in a callout.",
tags: new[] { "address", "geocode", "locate", "reverse geocode", "search" })]
public class ReverseGeocode : UIViewController
{
// Hold references to UI controls.
private MapView _myMapView;
// Service Uri to be provided to the LocatorTask (geocoder).
private readonly Uri _serviceUri = new Uri("https://geocode-api.arcgis.com/arcgis/rest/services/World/GeocodeServer");
// The LocatorTask provides geocoding services.
private LocatorTask _geocoder;
public ReverseGeocode()
{
Title = "Reverse geocode";
}
private async void Initialize()
{
// Create new Map with basemap.
Map myMap = new Map(BasemapStyle.ArcGISImagery);
// Provide used Map to the MapView.
_myMapView.Map = myMap;
// Add a graphics overlay to the map for showing where the user tapped.
_myMapView.GraphicsOverlays.Add(new GraphicsOverlay());
// Initialize the LocatorTask with the provided service Uri.
try
{
_geocoder = await LocatorTask.CreateAsync(_serviceUri);
}
catch (Exception e)
{
new UIAlertView("Error", e.ToString(), (IUIAlertViewDelegate) null, "OK", null).Show();
}
// Set the initial viewpoint.
await _myMapView.SetViewpointCenterAsync(34.058, -117.195, 5e4);
}
private async void _myMapView_GeoViewTapped(object sender, GeoViewInputEventArgs e)
{
try
{
// Clear the existing graphics & callouts.
_myMapView.DismissCallout();
_myMapView.GraphicsOverlays[0].Graphics.Clear();
// Add a graphic for the tapped point.
Graphic pinGraphic = await GraphicForPoint(e.Location);
_myMapView.GraphicsOverlays[0].Graphics.Add(pinGraphic);
// Normalize the geometry - needed if the user crosses the international date line.
MapPoint normalizedPoint = (MapPoint) GeometryEngine.NormalizeCentralMeridian(e.Location);
// Reverse geocode to get addresses.
IReadOnlyList<GeocodeResult> addresses = await _geocoder.ReverseGeocodeAsync(normalizedPoint);
// Get the first result.
GeocodeResult address = addresses.First();
// Use the city and region for the Callout Title.
string calloutTitle = address.Attributes["Address"].ToString();
// Use the metro area for the Callout Detail.
string calloutDetail = address.Attributes["City"] +
" " + address.Attributes["Region"] +
" " + address.Attributes["CountryCode"];
// Define the callout.
CalloutDefinition calloutBody = new CalloutDefinition(calloutTitle, calloutDetail);
// Show the callout on the map at the tapped location.
_myMapView.ShowCalloutForGeoElement(pinGraphic, e.Position, calloutBody);
}
catch (Exception ex)
{
Debug.WriteLine(ex);
new UIAlertView("No results", "No results found.", (IUIAlertViewDelegate) null, "OK", null).Show();
}
}
private async Task<Graphic> GraphicForPoint(MapPoint point)
{
// Get current assembly that contains the image.
Assembly currentAssembly = Assembly.GetExecutingAssembly();
// Get image as a stream from the resources.
// Picture is defined as EmbeddedResource and DoNotCopy.
Stream resourceStream = currentAssembly.GetManifestResourceStream(
"ArcGISRuntime.Resources.PictureMarkerSymbols.pin_star_blue.png");
// Create new symbol using asynchronous factory method from stream.
PictureMarkerSymbol pinSymbol = await PictureMarkerSymbol.CreateAsync(resourceStream);
pinSymbol.Width = 60;
pinSymbol.Height = 60;
// The image is a pin; offset the image so that the pinpoint
// is on the point rather than the image's true center.
pinSymbol.LeaderOffsetX = 30;
pinSymbol.OffsetY = 14;
return new Graphic(point, pinSymbol);
}
public override void LoadView()
{
// Create the views.
View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };
_myMapView = new MapView();
_myMapView.TranslatesAutoresizingMaskIntoConstraints = false;
UILabel helpLabel = new UILabel
{
Text = "Tap to find the nearest address.",
AdjustsFontSizeToFitWidth = true,
TextAlignment = UITextAlignment.Center,
BackgroundColor = UIColor.FromWhiteAlpha(0, .6f),
TextColor = UIColor.White,
Lines = 1,
TranslatesAutoresizingMaskIntoConstraints = false
};
// Add the views.
View.AddSubviews(_myMapView, helpLabel);
// Lay out the views.
NSLayoutConstraint.ActivateConstraints(new[]
{
_myMapView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
_myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
_myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
_myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
helpLabel.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
helpLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
helpLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
helpLabel.HeightAnchor.ConstraintEqualTo(40)
});
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
Initialize();
}
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
// Subscribe to events.
_myMapView.GeoViewTapped += _myMapView_GeoViewTapped;
}
public override void ViewDidDisappear(bool animated)
{
base.ViewDidDisappear(animated);
// Unsubscribe from events, per best practice.
_myMapView.GeoViewTapped -= _myMapView_GeoViewTapped;
}
}
}