Edit feature attachments

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Add, delete, and download attachments for features from a service.

Image of edit feature attachments

Use case

Attachments provide a flexible way to manage additional information that is related to your features. Attachments allow you to add files to individual features, including: PDFs, text documents, or any other type of file. For example, if you have a feature representing a building, you could use attachments to add multiple photographs of the building taken from several angles, along with PDF files containing the building's deed and tax information.

How to use the sample

Tap a feature to load its attachments. Use the buttons to save, delete, or add attachments.

How it works

  1. Create a ServiceFeatureTable from a URL.
  2. Create a FeatureLayer object from the service feature table.
  3. Select features from the feature layer with FeatureLayer.SelectFeatures().
  4. To fetch the feature's attachments, cast to an ArcGISFeature and useArcGISFeature.GetAttachmentsAsync().
  5. To add an attachment to the selected ArcGISFeature, create an attachment and use ArcGISFeature.AddAttachmentAsync().
  6. To delete an attachment from the selected ArcGISFeature, use the ArcGISFeature.DeleteAttachmentAsync().
  7. After a change, apply the changes to the server using ServiceFeatureTable.ApplyEditsAsync().

Additional information

Attachments can only be added to and accessed on service feature tables when their HasAttachments property is true.

Relevant API

  • ApplyEditsAsync
  • DeleteAttachmentAsync
  • FeatureLayer
  • FetchAttachmentsAsync
  • FetchDataAsync
  • ServiceFeatureTable
  • UpdateFeatureAsync

Tags

data, image, picture, JPEG, PNG, PDF, TXT

Sample Code

EditFeatureAttachments.cs
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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// 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.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.EditFeatureAttachments
{
    [Register("EditFeatureAttachments")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Edit feature attachments",
        category: "Data",
        description: "Add, delete, and download attachments for features from a service.",
        instructions: "Tap a feature to load its attachments. Use the buttons to save, delete, or add attachments.",
        tags: new[] { "JPEG", "PDF", "PNG", "TXT", "data", "image", "picture" })]
    public class EditFeatureAttachments : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;

        // Hold a reference to the layer.
        private FeatureLayer _damageLayer;

        // URL to the feature service.
        private const string FeatureServiceUrl = "https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0";

        public EditFeatureAttachments()
        {
            Title = "Edit feature attachments";
        }

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

            // Create the feature table, referring to the Damage Assessment feature service.
            ServiceFeatureTable damageTable = new ServiceFeatureTable(new Uri(FeatureServiceUrl));

            // Create a feature layer to visualize the features in the table.
            _damageLayer = new FeatureLayer(damageTable);

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

            // Zoom to the United States.
            _myMapView.SetViewpointCenterAsync(new MapPoint(-10800000, 4500000, SpatialReferences.WebMercator), 3e7);
        }

        private async void MapView_Tapped(object sender, GeoViewInputEventArgs e)
        {
            // Clear any existing selection.
            _damageLayer.ClearSelection();

            try
            {
                // Perform an identify to determine if a user tapped on a feature.
                IdentifyLayerResult identifyResult = await _myMapView.IdentifyLayerAsync(_damageLayer, e.Position, 2, false);

                // Do nothing if there are no results.
                if (!identifyResult.GeoElements.Any())
                {
                    return;
                }

                // Get the selected feature as an ArcGISFeature. It is assumed that all GeoElements in the result are of type ArcGISFeature.
                GeoElement tappedElement = identifyResult.GeoElements.First();
                ArcGISFeature tappedFeature = (ArcGISFeature) tappedElement;

                // Select the feature.
                _damageLayer.SelectFeature(tappedFeature);

                // Create the view controller.
                AttachmentsTableView attachmentsTableViewController = new AttachmentsTableView(tappedFeature);

                // Present the view controller.
                NavigationController.PushViewController(attachmentsTableViewController, true);

                // Deselect the feature.
                _damageLayer.ClearSelection();
            }
            catch (Exception ex)
            {
                ShowMessage(ex.ToString(), "Error selecting feature");
            }
        }

        private void ShowMessage(string message, string title)
        {
            // Create the alert controller.
            UIAlertController alertController = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
            alertController.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));

            // Show the alert.
            PresentViewController(alertController, true, null);
        }

        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 select features.",
                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 += MapView_Tapped;
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            // Unsubscribe from events, per best practice.
            _myMapView.GeoViewTapped -= MapView_Tapped;
        }
    }

    public class AttachmentsTableView : UITableViewController
    {
        private readonly ArcGISFeature _feature;

        public AttachmentsTableView(ArcGISFeature feature)
        {
            _feature = feature;
            Title = $"Attachments for #{feature.Attributes["objectid"]}";
        }

        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);
            Initialize();
        }

        private async void Initialize()
        {
            try
            {
                // Load the feature.
                await _feature.LoadAsync();

                // Get the attachments.
                IReadOnlyList<Attachment> attachments = await _feature.GetAttachmentsAsync();

                // Configure the view source.
                AttachmentsTableSource tableViewSource = new AttachmentsTableSource(this, _feature, attachments);

                // Add the source to the tableview.
                TableView.Source = tableViewSource;

                // Show the edit button in the navigation bar.
                NavigationItem.RightBarButtonItem = EditButtonItem;

                // Reload the tableview.
                TableView.ReloadData();
            }
            catch (Exception e)
            {
                ShowMessage(e.ToString(), "Error loading attachments");
            }
        }

        private void ShowMessage(string message, string title)
        {
            // Create the alert controller.
            UIAlertController alertController = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
            alertController.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));

            // Show the alert.
            PresentViewController(alertController, true, null);
        }

        private class AttachmentsTableSource : UITableViewSource
        {
            private readonly AttachmentsTableView _viewController;
            private readonly ArcGISFeature _selectedFeature;
            private IReadOnlyList<Attachment> _attachments;
            private TaskCompletionSource<Stream> _taskCompletionSource;
            private UIImagePickerController _imagePicker;
            private string _filename;

            public AttachmentsTableSource(AttachmentsTableView controller, ArcGISFeature selectedFeature, IReadOnlyList<Attachment> attachments)
            {
                _attachments = attachments.Where(attachment => attachment.ContentType == "image/jpeg").ToList();
                _selectedFeature = selectedFeature;
                _viewController = controller;
            }

            // These methods tell the table view what to show.

            #region table view source overrides

            public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
            {
                // Gets a cell for the specified row.
                UITableViewCell cell;

                // If the cell represents an attachment, get an attachment cell.
                if (indexPath.Row < _attachments.Count)
                {
                    cell = new UITableViewCell(UITableViewCellStyle.Default, "AttachmentCell");
                    cell.TextLabel.Text = _attachments[indexPath.Row].Name;
                    cell.Accessory = UITableViewCellAccessory.DisclosureIndicator;
                    return cell;
                }

                // Otherwise, show the 'add attachment' cell.
                cell = new UITableViewCell(UITableViewCellStyle.Default, "InsertCell");
                cell.TextLabel.Text = "Add attachment";
                cell.Accessory = UITableViewCellAccessory.Checkmark;
                return cell;
            }

            public override nint RowsInSection(UITableView tableview, nint section)
            {
                if (section == 0)
                {
                    // The extra row is the 'add attachment' row.
                    return _attachments?.Count + 1 ?? 0;
                }

                return 0;
            }

            public override void CommitEditingStyle(UITableView tableView, UITableViewCellEditingStyle editingStyle, NSIndexPath indexPath)
            {
                // Commit editing - in this case, editing means insertion or deletion.
                switch (editingStyle)
                {
                    case UITableViewCellEditingStyle.Delete:
                        Attachment selectedAttachment = _attachments[indexPath.Row];
                        DeleteAttachment(selectedAttachment, tableView);
                        break;
                    case UITableViewCellEditingStyle.Insert:
                        AddAttachment(tableView);
                        break;
                }

                // Force the view to reload its data.
                tableView.ReloadData();
            }

            public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
            {
                // If the row doesn't represent an attachment, it is the insert row.
                if (indexPath.Row >= _attachments.Count)
                {
                    // Insert row was selected, add a new attachment.
                    AddAttachment(tableView);

                    // Force the view to reload its data.
                    tableView.ReloadData();
                }
                else
                {
                    // An existing attachment was selected, show the preview.
                    PreviewAttachment(_attachments[indexPath.Row]);
                }
            }

            public override string TitleForDeleteConfirmation(UITableView tableView, NSIndexPath indexPath)
            {
                return "Delete attachment";
            }

            public override bool CanEditRow(UITableView tableView, NSIndexPath indexPath)
            {
                // All rows are editable.
                return true;
            }

            public override UITableViewCellEditingStyle EditingStyleForRow(UITableView tableView, NSIndexPath indexPath)
            {
                // If there is an attachment for the row, the editing style is deletion.
                if (indexPath.Row < _attachments.Count)
                {
                    return UITableViewCellEditingStyle.Delete;
                }

                // Otherwise, this is the insert row, so use the 'Insert' editing style.
                return UITableViewCellEditingStyle.Insert;
            }

            #endregion table view source overrides

            #region attachment actions

            private async void AddAttachment(UITableView tableView)
            {
                // Get the image to upload.
                Stream imageStream = await GetImageStreamAsync();
                if (imageStream == null)
                {
                    return;
                }

                // Convert the image stream into a byte array.
                byte[] attachmentData = new byte[imageStream.Length];
                imageStream.Read(attachmentData, 0, attachmentData.Length);

                // Determine the file name.
                string filename = _filename ?? "iOS_image_1.jpg";

                // Add the attachment.
                // The contentType string is the MIME type for JPEG files, image/jpeg.
                await _selectedFeature.AddAttachmentAsync(filename, "image/jpeg", attachmentData);

                // Get a reference to the feature's service feature table.
                ServiceFeatureTable serviceTable = (ServiceFeatureTable) _selectedFeature.FeatureTable;

                // Apply the edits to the service feature table.
                await serviceTable.ApplyEditsAsync();

                // Update UI.
                _selectedFeature.Refresh();
                _attachments = await _selectedFeature.GetAttachmentsAsync();
                tableView.ReloadData();
                _viewController.ShowMessage("Successfully added attachment", "Success!");
            }

            private async void DeleteAttachment(Attachment attachmentToDelete, UITableView tableView)
            {
                try
                {
                    // Delete the attachment.
                    await _selectedFeature.DeleteAttachmentAsync(attachmentToDelete);

                    // Get a reference to the feature's service feature table.
                    ServiceFeatureTable serviceTable = (ServiceFeatureTable) _selectedFeature.FeatureTable;

                    // Apply the edits to the service feature table.
                    await serviceTable.ApplyEditsAsync();

                    // Update UI.
                    _selectedFeature.Refresh();
                    _attachments = await _selectedFeature.GetAttachmentsAsync();
                    tableView.ReloadData();
                    _viewController.ShowMessage("Successfully deleted attachment", "Success!");
                }
                catch (Exception exception)
                {
                    _viewController.ShowMessage(exception.ToString(), "Error deleting attachment");
                }
            }

            private async void PreviewAttachment(Attachment selectedAttachment)
            {
                if (selectedAttachment.ContentType.Contains("image"))
                {
                    // Get the image data.
                    Stream contentStream = await selectedAttachment.GetDataAsync();
                    var imageData = NSData.FromStream(contentStream);

                    // Create a native iOS image from the image data.
                    var image = UIImage.LoadFromData(imageData);

                    // Create a view to show the image.
                    UIImageView imageView = new UIImageView(image);

                    // Configure the view's appearance.
                    imageView.TranslatesAutoresizingMaskIntoConstraints = false;
                    imageView.ContentMode = UIViewContentMode.ScaleAspectFit;
                    // A view controller is needed to show the view.
                    var imagePreviewVC = new UIViewController();
                    imagePreviewVC.View = new UIView {BackgroundColor = ApplicationTheme.BackgroundColor};
                    imagePreviewVC.View.AddSubview(imageView);
                    imagePreviewVC.Title = "Attachment preview";
                    NSLayoutConstraint.ActivateConstraints(new[]
                    {
                        imageView.TopAnchor.ConstraintEqualTo(imagePreviewVC.View.SafeAreaLayoutGuide.TopAnchor),
                        imageView.LeftAnchor.ConstraintEqualTo(imagePreviewVC.View.SafeAreaLayoutGuide.LeftAnchor),
                        imageView.RightAnchor.ConstraintEqualTo(imagePreviewVC.View.SafeAreaLayoutGuide.RightAnchor),
                        imageView.BottomAnchor.ConstraintEqualTo(imagePreviewVC.View.SafeAreaLayoutGuide.BottomAnchor)
                    });

                    // Show the preview.
                    _viewController.NavigationController.PushViewController(imagePreviewVC, true);
                }
                else
                {
                    _viewController.ShowMessage("This sample can only show image attachments", "Can't show attachment");
                }
            }

            #endregion attachment actions

            #region file picker

            // Note: this code is adapted from https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/dependency-service/photo-picker
            private Task<Stream> GetImageStreamAsync()
            {
                // Create and define the UIImagePickerController.
                _imagePicker = new UIImagePickerController
                {
                    SourceType = UIImagePickerControllerSourceType.PhotoLibrary,
                    MediaTypes = UIImagePickerController.AvailableMediaTypes(UIImagePickerControllerSourceType.PhotoLibrary)
                };

                // Set event handlers.
                _imagePicker.FinishedPickingMedia += OnImagePickerFinishedPickingMedia;
                _imagePicker.Canceled += OnImagePickerCancelled;

                // Present UIImagePickerController.
                UIWindow window = UIApplication.SharedApplication.KeyWindow;
                var viewController = window.RootViewController;
                viewController.PresentModalViewController(_imagePicker, true);

                // Return Task object.
                _taskCompletionSource = new TaskCompletionSource<Stream>();
                return _taskCompletionSource.Task;
            }

            private void OnImagePickerFinishedPickingMedia(object sender, UIImagePickerMediaPickedEventArgs args)
            {
                // This is called when the user has finished making their selection.

                // Get the image - either with edits or without.
                UIImage image = args.EditedImage ?? args.OriginalImage;

                // Get the name of the file.
                _filename = args.ImageUrl.LastPathComponent;

                UnregisterEventHandlers();

                if (image != null)
                {
                    // Convert iOS image to .NET Stream.
                    NSData data = image.AsJPEG(1);
                    Stream stream = data.AsStream();

                    // Set the Stream as the completion of the Task.
                    _taskCompletionSource.SetResult(stream);
                }
                else
                {
                    _taskCompletionSource.SetResult(null);
                }

                // Hide the picker view.
                _imagePicker.DismissModalViewController(true);
            }

            private void OnImagePickerCancelled(object sender, EventArgs args)
            {
                // Handle cancellation.
                UnregisterEventHandlers();
                _taskCompletionSource.SetResult(null);
                _imagePicker.DismissModalViewController(true);
            }

            private void UnregisterEventHandlers()
            {
                // Clean up when done picking image.
                _imagePicker.FinishedPickingMedia -= OnImagePickerFinishedPickingMedia;
                _imagePicker.Canceled -= OnImagePickerCancelled;
            }

            #endregion file picker
        }
    }
}

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