List related features

This sample demonstrates how to query features related to an identified feature.

List related features

Instructions

Click on a feature to identify it. Related features will be listed in the window above the map.

Code

// Copyright 2018 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 Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.Linq;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.ListRelatedFeatures
{
    [Register("ListRelatedFeatures")]
    public class ListRelatedFeatures : UIViewController
    {
        // URL to the web map
        private readonly Uri _mapUri =
            new Uri("https://arcgisruntime.maps.arcgis.com/home/item.html?id=dcc7466a91294c0ab8f7a094430ab437");

        // Reference to the feature layer
        private FeatureLayer _myFeatureLayer;

        // Create and hold reference to the used MapView
        private MapView _myMapView = new MapView();

        // Hold a source for the UITableView that shows the related features
        private LayerListSource _layerListSource;

        // Create the view for the layer list display
        private UITableView _myDisplayList = new UITableView();

        public ListRelatedFeatures()
        {
            Title = "List related features";
        }

        private async void Initialize()
        {
            // Create the portal item from the URL to the webmap
            PortalItem alaskaPortalItem = await PortalItem.CreateAsync(_mapUri);

            // Create the map from the portal item
            Map myMap = new Map(alaskaPortalItem);

            // Add the map to the mapview
            _myMapView.Map = myMap;

            // Wait for the map to load
            await myMap.LoadAsync();

            // Get the feature layer from the map
            _myFeatureLayer = (FeatureLayer)myMap.OperationalLayers.First();

            // Make the selection color yellow and the width thick
            _myFeatureLayer.SelectionColor = System.Drawing.Color.Yellow;
            _myFeatureLayer.SelectionWidth = 5;

            // Listen for GeoViewTapped events
            _myMapView.GeoViewTapped += MyMapViewOnGeoViewTapped;
        }

        private async void MyMapViewOnGeoViewTapped(object sender, GeoViewInputEventArgs e)
        {
            // Clear any existing feature selection and results list
            _myFeatureLayer.ClearSelection();
            _myDisplayList.Source = null; 
            _myDisplayList.ReloadData();

            // Identify the tapped feature
            IdentifyLayerResult results = await _myMapView.IdentifyLayerAsync(_myFeatureLayer, e.Position, 10, false);

            // Return if there are no results
            if (results.GeoElements.Count < 1) { return; }

            // Get the first result
            ArcGISFeature myFeature = (ArcGISFeature)results.GeoElements.First();

            // Select the feature
            _myFeatureLayer.SelectFeature(myFeature);

            // Get the feature table for the feature
            ArcGISFeatureTable myFeatureTable = (ArcGISFeatureTable)myFeature.FeatureTable;

            // Query related features
            IReadOnlyList<RelatedFeatureQueryResult> relatedFeaturesResult = await myFeatureTable.QueryRelatedFeaturesAsync(myFeature);

            // Create a list to hold the formatted results of the query
            List<String> queryResultsForUi = new List<string>();

            // For each query result
            foreach (RelatedFeatureQueryResult result in relatedFeaturesResult)
            {
                // And then for each feature in the result
                foreach (Feature resultFeature in result)
                {
                    // Get a reference to the feature's table
                    ArcGISFeatureTable relatedTable = (ArcGISFeatureTable)resultFeature.FeatureTable;

                    // Get the display field name - this is the name of the field that is intended for display
                    string displayFieldName = relatedTable.LayerInfo.DisplayFieldName;

                    // Get the name of the feature's table
                    string tableName = relatedTable.TableName;

                    // Get the display name for the feature
                    string featureDisplayname = resultFeature.Attributes[displayFieldName].ToString();

                    // Create a formatted result string
                    string formattedResult = String.Format("{0} - {1}", tableName, featureDisplayname);

                    // Add the result to the list
                    queryResultsForUi.Add(formattedResult);
                }
            }

            // Create the source for the display list
            _layerListSource = new LayerListSource(queryResultsForUi);

            // Assign the source to the display view
            _myDisplayList.Source = _layerListSource;

            // Force the table view to refresh its data
            _myDisplayList.ReloadData();
        }

        private void CreateLayout()
        {
            // Add MapView to the page
            View.AddSubviews(_myMapView);

            // Create the table view
            _myDisplayList = new UITableView();

            // Add the table view to the layout
            View.AddSubview(_myDisplayList);
        }

        public override void ViewDidLoad()
        {
            CreateLayout();
            Initialize();

            base.ViewDidLoad();
        }

        public override void ViewDidLayoutSubviews()
        {
            // Variable holding the top bound (for code clarity)
            nfloat pageOffset = this.NavigationController.TopLayoutGuide.Length;

            // Set up the visual frame for the layer display list
            _myDisplayList.Frame = new CoreGraphics.CGRect(0, pageOffset, View.Bounds.Width, 150);

            // Set up the visual frame for the MapView
            _myMapView.Frame = new CoreGraphics.CGRect(0, 0, View.Bounds.Width, View.Bounds.Height);

            base.ViewDidLayoutSubviews();
        }
    }
    /// <summary>
    /// Class defines how a UITableView renders its contents.
    /// This implements the UI for the list of related features
    /// </summary>
    public class LayerListSource : UITableViewSource
    {
        // List of strings;
        public List<string> _viewModelList = new List<string>();

        // Used when re-using cells to ensure that a cell of the right type is used
        private string CellId = "TableCell";

        public LayerListSource(List<string> items)
        {
            // Set the items
            if (items != null)
            {
                _viewModelList = items;
            }
        }

        /// <summary>
        /// This method gets a table view cell for the suggestion at the specified index
        /// </summary>
        public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
        {
            // Try to get a re-usable cell (this is for performance)
            UITableViewCell cell = tableView.DequeueReusableCell(CellId);

            // If there are no cells, create a new one
            if (cell == null)
            {
                cell = new UITableViewCell(UITableViewCellStyle.Default, CellId);
            }

            // Get the specific item to display
            string item = _viewModelList[indexPath.Row];

            // Set the text on the cell
            cell.TextLabel.Text = item;
            
            // Ensure that the label fits
            cell.TextLabel.AdjustsFontSizeToFitWidth = true;

            // Return the cell
            return cell;
        }

        /// <summary>
        /// This method allows the UITableView to know how many rows to render
        /// </summary>
        public override nint RowsInSection(UITableView tableview, nint section)
        {
            return _viewModelList.Count;
        }
    }
}


In this topic
  1. Instructions
  2. Code