List related features

View inWPFUWPFormsiOSAndroid
View on GitHub

List features related to the selected feature.

Image of list related features

Use case

Related features are useful for managing relational information, like what you would store in a relational database management system (RDBMS). You can define relationship between records as one-to-one, one-to-many, or many-to-one. For example, you could model inspections and facilities as a many-to-one relationship. Then, for any facility feature, you could list related inspection features.

How to use the sample

Tap on a feature to select it. The related features will be displayed in a list.

How it works

  1. With a Feature, call QueryRelatedFeaturesAsync on the feature's feature table.
  2. Iterate over the result's collection of RelatedFeatureQueryResult objects to get the related features and add them to a list.

Relevant API

  • ArcGISFeature
  • ArcGISFeatureTable
  • FeatureQueryResult
  • FeatureTable.QueryRelatedFeatures
  • RelatedFeatureQueryResult

Tags

features, identify, query, related, relationship, search

Sample Code

ListRelatedFeatures.cs
                                                                                                                                                                                                                                                                                                           
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
// 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 System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.ListRelatedFeatures
{
    [Register("ListRelatedFeatures")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "List related features",
        category: "Data",
        description: "List features related to the selected feature.",
        instructions: "Tap on a feature to select it. The related features will be displayed in a list.",
        tags: new[] { "features", "identify", "query", "related", "relationship", "search" })]
    public class ListRelatedFeatures : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;
        private UITableView _tableView;
        private NSLayoutConstraint[] _portraitConstraints;
        private NSLayoutConstraint[] _landscapeConstraints;

        // 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;

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

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

        private async void Initialize()
        {
            try
            {
                // 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();

                // Update the selection color.
                _myMapView.SelectionProperties.Color = Color.Yellow;
            }
            catch (Exception e)
            {
                new UIAlertView("Error", e.ToString(), (IUIAlertViewDelegate) null, "OK", null).Show();
            }
        }

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

            try
            {
                // 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 = $"{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.
                _tableView.Source = _layerListSource;

                // Force the table view to refresh its data.
                _tableView.ReloadData();
            }
            catch (Exception ex)
            {
                new UIAlertView("Error", ex.ToString(), (IUIAlertViewDelegate) null, "OK", null).Show();
            }
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void LoadView()
        {
            // Create the views.
            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            _tableView = new UITableView();
            _tableView.TranslatesAutoresizingMaskIntoConstraints = false;
            _tableView.RowHeight = 30;

            View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };

            // Add the views.
            View.AddSubviews(_myMapView, _tableView);

            // Lay out the views.
            _portraitConstraints = new[]
            {
                _tableView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _tableView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _tableView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _tableView.HeightAnchor.ConstraintEqualTo(_tableView.RowHeight * 4),

                _myMapView.TopAnchor.ConstraintEqualTo(_tableView.BottomAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor)
            };

            _landscapeConstraints = new[]
            {
                _tableView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _tableView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _tableView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _tableView.TrailingAnchor.ConstraintEqualTo(View.CenterXAnchor),

                _myMapView.TopAnchor.ConstraintEqualTo(View.TopAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(_tableView.TrailingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor)
            };

            // Activate default constraints.
            if (View.TraitCollection.VerticalSizeClass == UIUserInterfaceSizeClass.Compact)
            {
                NSLayoutConstraint.ActivateConstraints(_landscapeConstraints);
            }
            else
            {
                NSLayoutConstraint.ActivateConstraints(_portraitConstraints);
            }
        }

        public override void TraitCollectionDidChange(UITraitCollection previousTraitCollection)
        {
            base.TraitCollectionDidChange(previousTraitCollection);

            // Reset constraints.
            NSLayoutConstraint.DeactivateConstraints(_portraitConstraints);
            NSLayoutConstraint.DeactivateConstraints(_landscapeConstraints);

            if (View.TraitCollection.VerticalSizeClass == UIUserInterfaceSizeClass.Compact)
            {
                NSLayoutConstraint.ActivateConstraints(_landscapeConstraints);
            }
            else
            {
                NSLayoutConstraint.ActivateConstraints(_portraitConstraints);
            }
        }

        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;
        }
    }

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

        // Used when re-using cells to ensure that a cell of the right type is used.
        private const 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). If there are no cells, create a new one.
            UITableViewCell cell = tableView.DequeueReusableCell(CellId);
            if (cell == null)
            {
                cell = new UITableViewCell(UITableViewCellStyle.Default, CellId);
            }

            // Set the text on the cell.
            cell.TextLabel.Text = _viewModelList[indexPath.Row];

            // 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;
        }
    }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.