Add, delete, and download attachments for features from a service.
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
- Create a
ServiceFeatureTablefrom a URL. - Create a
FeatureLayerobject from the service feature table. - Select features from the feature layer with
FeatureLayer.SelectFeatures(). - To fetch the feature's attachments, cast to an
ArcGISFeatureand useArcGISFeature.GetAttachmentsAsync(). - To add an attachment to the selected ArcGISFeature, create an attachment and use
ArcGISFeature.AddAttachmentAsync(). - To delete an attachment from the selected ArcGISFeature, use the
ArcGISFeature.DeleteAttachmentAsync(). - 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
// 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 Android.App;
using Android.OS;
using Android.Widget;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Android.Content;
using Android.Graphics;
using Android.Views;
namespace ArcGISRuntimeXamarin.Samples.EditFeatureAttachments
{
[Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
[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 : Activity
{
// Hold references to the UI controls.
private MapView _myMapView;
private ListView _attachmentsListView;
private Button _addButton;
// Hold a reference to the layer.
private FeatureLayer _damageLayer;
// Hold references to the currently selected feature & any attachments.
private ArcGISFeature _selectedFeature;
private IReadOnlyList<Attachment> _featureAttachments;
// URL to the feature service.
private const string FeatureServiceUrl = "https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0";
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
Title = "Edit feature attachments";
CreateLayout();
Initialize();
}
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);
// Listen for user taps on the map.
_myMapView.GeoViewTapped += MapView_Tapped;
// 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();
_addButton.Enabled = false;
_attachmentsListView.Enabled = false;
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();
_selectedFeature = (ArcGISFeature) tappedElement;
// Update the UI.
UpdateUIForFeature();
_addButton.Enabled = true;
_attachmentsListView.Enabled = true;
}
catch (Exception ex)
{
ShowMessage(ex.ToString(), "Error selecting feature");
}
}
private async void UpdateUIForFeature()
{
// Select the feature.
_damageLayer.SelectFeature(_selectedFeature);
// Get the attachments.
_featureAttachments = await _selectedFeature.GetAttachmentsAsync();
// Limit to only feature attachments with an image/jpeg content type.
_featureAttachments = _featureAttachments.Where(attachment => attachment.ContentType == "image/jpeg").ToList();
// Configure array adapter.
ArrayAdapter attachmentAdapter = new ArrayAdapter<string>(
this,
Android.Resource.Layout.SimpleListItem1,
_featureAttachments.Select(attachment => attachment.Name).ToArray());
// Populate the list.
_attachmentsListView.Adapter = attachmentAdapter;
}
private async Task PreviewAttachment(Attachment selectedAttachment)
{
if (selectedAttachment.ContentType.Contains("image"))
{
// Get the image data.
Stream contentStream = await selectedAttachment.GetDataAsync();
byte[] attachmentData = new byte[contentStream.Length];
contentStream.Read(attachmentData, 0, attachmentData.Length);
// Convert the image into a usable form on Android.
Bitmap bmp = BitmapFactory.DecodeByteArray (attachmentData, 0, attachmentData.Length);
// Create the view that will present the image.
ImageView imageView = new ImageView(this);
imageView.SetImageBitmap(bmp);
// Show the image view in a dialog.
ShowImageDialog(imageView);
}
else
{
ShowMessage("This sample can only show image attachments", "Can't show attachment");
}
}
private void ShowImageDialog(ImageView previewImageView)
{
// Create the dialog.
Dialog imageDialog = new Dialog(this);
// Remove the title bar for the dialog.
imageDialog.Window.RequestFeature(WindowFeatures.NoTitle);
// Add the image to the dialog.
imageDialog.SetContentView(previewImageView);
// Show the dialog.
imageDialog.Show();
}
private async Task DeleteAttachment(Attachment attachmentToDelete)
{
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();
_featureAttachments = await _selectedFeature.GetAttachmentsAsync();
UpdateUIForFeature();
ShowMessage("Successfully deleted attachment", "Success!");
}
catch (Exception exception)
{
ShowMessage(exception.ToString(), "Error deleting attachment");
}
}
private void RequestImage()
{
// Start the process of requesting an image. Will be completed in OnActivityResult.
Intent = new Intent();
Intent.SetType("image/*");
Intent.SetAction(Intent.ActionGetContent);
StartActivityForResult(Intent.CreateChooser(Intent, "Select Picture"), 1000);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
// Method called when the image picker activity ends.
if (requestCode == 1000 && resultCode == Result.Ok && data != null)
{
// Get the path to the selected image.
Android.Net.Uri uri = data.Data;
// Upload the image as an attachment.
AddAttachment(uri);
}
else
{
ShowMessage("No image selected.", "Error adding attachment");
}
}
private async void AddAttachment(Android.Net.Uri imageUri)
{
string contentType = "image/jpeg";
// Read the image into a stream.
Stream stream = ContentResolver.OpenInputStream(imageUri);
// Read from the stream into the byte array.
byte[] attachmentData;
using (var memoryStream = new MemoryStream())
{
stream.CopyTo(memoryStream);
attachmentData = memoryStream.ToArray();
}
// Add the attachment.
// The contentType string is the MIME type for JPEG files, image/jpeg.
await _selectedFeature.AddAttachmentAsync(imageUri.LastPathSegment + ".jpg", contentType, 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();
_featureAttachments = await _selectedFeature.GetAttachmentsAsync();
UpdateUIForFeature();
ShowMessage("Successfully added attachment", "Success!");
}
private void Attachment_Clicked(object sender, AdapterView.ItemClickEventArgs e)
{
// Get the selected attachment.
Attachment selectedAttachment = _featureAttachments[e.Position];
// Create menu to show options.
PopupMenu menu = new PopupMenu(this, (ListView) sender);
// Handle the click, calling the right method depending on the command.
menu.MenuItemClick += async (o, menuArgs) =>
{
menu.Dismiss();
switch (menuArgs.Item.ToString())
{
case "View":
await PreviewAttachment(selectedAttachment);
break;
case "Delete":
await DeleteAttachment(selectedAttachment);
break;
}
UpdateUIForFeature();
};
// Add the menu commands.
menu.Menu.Add("View");
menu.Menu.Add("Delete");
// Show menu in the view.
menu.Show();
}
private void ShowMessage(string message, string title)
{
// Display the message to the user.
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.SetMessage(message).SetTitle(title).Show();
}
private void CreateLayout()
{
// Create a new vertical layout for the app.
var layout = new LinearLayout(this) {Orientation = Orientation.Vertical};
// Create the MapView.
_myMapView = new MapView(this);
// Create the help label.
TextView helpLabel = new TextView(this);
helpLabel.Text = "Tap to select features.";
helpLabel.TextAlignment = TextAlignment.Center;
helpLabel.Gravity = GravityFlags.Center;
// Add the help label to the layout.
layout.AddView(helpLabel);
// Create and add a listview for showing attachments;
_attachmentsListView = new ListView(this);
_attachmentsListView.Enabled = false;
_attachmentsListView.SetMinimumHeight(100);
layout.AddView(_attachmentsListView);
_attachmentsListView.ItemClick += Attachment_Clicked;
// Create and add an 'add attachment' button.
_addButton = new Button(this);
_addButton.Text = "Add attachment";
_addButton.Enabled = false;
_addButton.Click += AddButton_Clicked;
layout.AddView(_addButton);
// Add the map view to the layout.
layout.AddView(_myMapView);
// Show the layout in the app.
SetContentView(layout);
}
private void AddButton_Clicked(object sender, EventArgs e)
{
// Do nothing if nothing selected.
if (_selectedFeature == null)
{
return;
}
// Start the process of requesting an image to add.
RequestImage();
}
}
}