Browse OGC API feature service

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Browse an OGC API feature service for layers and add them to the map.

Image of browse OGC API feature service

Use case

OGC API standards are used for sharing geospatial data on the web. As an open standard, the OGC API aims to improve access to geospatial or location information and could be a good choice for sharing data internationally or between organizations. That data could be of any type, including, for example transportation layers shared between government organizations and private businesses.

How to use the sample

Select a layer to display from the list of layers shown in an OGC API service.

How it works

  1. Create an OgcFeatureService object with a URL to an OGC API feature service.
  2. Obtain the OgcFeatureServiceInfo from OgcFeatureService.ServiceInfo.
  3. Create a list of feature collections from the OgcFeatureServiceInfo.FeatureCollectionInfos
  4. When a feature collection is selected, create an OgcFeatureCollectionTable from the OgcFeatureCollectionInfo.
  5. Populate the OgcFeatureCollectionTable using PopulateFromServiceAsync with QueryParameters that contain a MaxFeatures property.
  6. Create a feature layer from the feature table.
  7. Add the feature layer to the map.

Relevant API

  • OgcFeatureCollectionInfo
  • OgcFeatureCollectionTable
  • OgcFeatureService
  • OgcFeatureServiceInfo

About the data

The Daraa, Syria test data is OpenStreetMap data converted to the Topographic Data Store schema of NGA.

Additional information

See the OGC API website for more information on the OGC API family of standards.

Tags

browse, catalog, feature, layers, OGC, OGC API, service, web

Sample Code

BrowseOAFeatureService.cs
                                                                                                                                                                                                                                                   
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// Copyright 2021 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 Android.App;
using Android.Content;
using Android.OS;
using Android.Views;
using Android.Widget;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Ogc;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.UI.Controls;
using System;
using System.Drawing;

namespace ArcGISRuntimeXamarin.Samples.BrowseOAFeatureService
{
    [Activity(ConfigurationChanges = Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Browse OGC API feature service",
        category: "Layers",
        description: "Browse an OGC API feature service for layers and add them to the map.",
        instructions: "Select a layer to display from the list of layers shown in an OGC API service.",
        tags: new[] { "OGC", "OGC API", "browse", "catalog", "feature", "layers", "service", "web" })]
    public class BrowseOAFeatureService : Activity
    {
        // Hold references to the UI controls.
        private MapView _myMapView;
        private ProgressBar _loadingProgressBar;
        private Button _loadLayerButton;
        private Button _loadServiceButton;
        private EditText _urlEntry;

        // URL for the OGC feature service.
        private const string _serviceUrl = "https://demo.ldproxy.net/daraa";

        private OgcFeatureServiceInfo _serviceInfo;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            Title = "Browse OGC API feature service";

            CreateLayout();
            Initialize();
        }

        private void Initialize()
        {
            // Create the map with topographic basemap.
            _myMapView.Map = new Map(BasemapStyle.ArcGISTopographic);

            LoadService(_serviceUrl);
        }

        private async void LoadService(string serviceUrl)
        {
            try
            {
                _loadingProgressBar.Visibility = ViewStates.Visible;
                _loadLayerButton.Enabled = false;
                _loadServiceButton.Enabled = false;

                // Create the OGC API - Features service using the landing URL.
                OgcFeatureService service = new OgcFeatureService(new Uri(serviceUrl));

                // Load the service.
                await service.LoadAsync();

                // Get the service metadata.
                _serviceInfo = service.ServiceInfo;
            }
            catch (Exception ex)
            {
                new AlertDialog.Builder(this).SetMessage(ex.Message).SetTitle("Error loading service").Show();
            }
            finally
            {
                // Update the UI.
                _loadingProgressBar.Visibility = ViewStates.Gone;
                _loadLayerButton.Enabled = true;
                _loadServiceButton.Enabled = true;
            }
        }

        private async void LayerMenu_LayerSelected(object sender, PopupMenu.MenuItemClickEventArgs e)
        {
            // Show the progress bar.
            _loadingProgressBar.Visibility = ViewStates.Visible;

            // Clear the existing layers.
            _myMapView.Map.OperationalLayers.Clear();

            try
            {
                // Get the selected collection.
                OgcFeatureCollectionInfo selectedCollectionInfo = _serviceInfo.FeatureCollectionInfos[e.Item.Order];

                // Create the OGC feature collection table.
                OgcFeatureCollectionTable table = new OgcFeatureCollectionTable(selectedCollectionInfo);

                // Set the feature request mode to manual (only manual is currently supported).
                // In this mode, you must manually populate the table - panning and zooming won't request features automatically.
                table.FeatureRequestMode = FeatureRequestMode.ManualCache;

                // Populate the OGC feature collection table.
                QueryParameters queryParamaters = new QueryParameters();
                queryParamaters.MaxFeatures = 1000;
                await table.PopulateFromServiceAsync(queryParamaters, false, null);

                // Create a feature layer from the OGC feature collection table.
                FeatureLayer ogcFeatureLayer = new FeatureLayer(table);

                // Choose a renderer for the layer based on the table.
                ogcFeatureLayer.Renderer = GetRendererForTable(table) ?? ogcFeatureLayer.Renderer;

                // Add the layer to the map.
                _myMapView.Map.OperationalLayers.Add(ogcFeatureLayer);

                // Zoom to the extent of the selected collection.
                if (selectedCollectionInfo.Extent is Envelope collectionExtent && !collectionExtent.IsEmpty)
                {
                    await _myMapView.SetViewpointGeometryAsync(collectionExtent, 100);
                }
            }
            catch (Exception exception)
            {
                System.Diagnostics.Debug.WriteLine(exception);
                new AlertDialog.Builder(this).SetMessage(exception.ToString()).SetTitle("Couldn't load layer.").Show();
            }
            finally
            {
                // Hide the progress bar.
                _loadingProgressBar.Visibility = ViewStates.Gone;
            }
        }

        private void ChooseLayer_Clicked(object sender, EventArgs e)
        {
            // Get a reference to the button.
            Button loadButton = (Button)sender;

            // Create menu to show layer options.
            PopupMenu layerMenu = new PopupMenu(this, loadButton);
            layerMenu.MenuItemClick += LayerMenu_LayerSelected;

            // Create menu options.
            int index = 0;
            foreach (OgcFeatureCollectionInfo layerInfo in _serviceInfo.FeatureCollectionInfos)
            {
                layerMenu.Menu.Add(0, index, index, layerInfo.Title);
                index++;
            }

            // Show menu in the view.
            layerMenu.Show();
        }

        private void ServiceClicked(object sender, EventArgs e)
        {
            // Create a text-entry prompt for changing the WFS url.
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.SetTitle("Set OGC API service URL");

            // Create the text entry.
            _urlEntry = new EditText(this);
            _urlEntry.Text = string.Empty;
            _urlEntry.InputType = Android.Text.InputTypes.TextVariationUri;
            builder.SetView(_urlEntry);

            // Finish building the dialog and display it.
            builder.SetPositiveButton("Load", ServicePressed);
            builder.SetCancelable(true);
            builder.Show();
        }

        private void ServicePressed(object sender, DialogClickEventArgs e)
        {
            LoadService(_urlEntry.Text);
        }

        private Renderer GetRendererForTable(FeatureTable table)
        {
            switch (table.GeometryType)
            {
                case GeometryType.Point:
                case GeometryType.Multipoint:
                    return new SimpleRenderer(new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Circle, Color.Blue, 4));

                case GeometryType.Polygon:
                case GeometryType.Envelope:
                    return new SimpleRenderer(new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Blue, null));

                case GeometryType.Polyline:
                    return new SimpleRenderer(new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Blue, 1));
            }

            return null;
        }

        private void CreateLayout()
        {
            // Create a new vertical layout for the app.
            var layout = new LinearLayout(this) { Orientation = Orientation.Vertical };

            // Add the button.
            _loadServiceButton = new Button(this);
            _loadServiceButton.Text = "Load service";
            _loadServiceButton.Click += ServiceClicked;
            _loadServiceButton.Enabled = false;
            layout.AddView(_loadServiceButton);

            // Add the button.
            _loadLayerButton = new Button(this);
            _loadLayerButton.Text = "Choose a layer";
            _loadLayerButton.Click += ChooseLayer_Clicked;
            _loadLayerButton.Enabled = false;
            layout.AddView(_loadLayerButton);

            // Add the loading indicator.
            _loadingProgressBar = new ProgressBar(this);
            _loadingProgressBar.Indeterminate = true;
            _loadingProgressBar.Visibility = ViewStates.Gone;
            layout.AddView(_loadingProgressBar);

            // Add the map view to the layout.
            _myMapView = new MapView(this);
            layout.AddView(_myMapView);

            // Show the layout in the app.
            SetContentView(layout);
        }
    }
}

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