Download preplanned map area

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Take a map offline using a preplanned map area.

Image of download preplanned map area

Use case

Generating offline maps on demand for a specific area can be time consuming for users and a processing load on the server. If areas of interest are known ahead of time, a web map author can pre-create packages for these areas. This way, the generation only needs to happen once, making the workflow more efficient for users and servers.

An archaeology team could define preplanned map areas for dig sites which can be taken offline for field use.

How to use the sample

Select a map area from the Preplanned Map Areas list. Tap the button to download the selected area. The download progress will be shown in the Downloads list. When a download is complete, select it to display the offline map in the map view.

How it works

  1. Open the online Map from a PortalItem and display it.
  2. Create an OfflineMapTask using the portal item.
  3. Get the PreplannedMapAreas from the task, and then load them.
  4. To download a selected map area, create the default DownloadPreplannedOfflineMapParameters from the task using the selected preplanned map area.
  5. Set the update mode of the preplanned map area.
  6. Use the parameters and a download path to create a DownloadPreplannedOfflineMapJob from the task.
  7. Start the job. Once it has completed, get the DownloadPreplannedOfflineMapResult.
  8. Get the Map from the result and display it in the MapView.

Relevant API

  • DownloadPreplannedOfflineMapJob
  • DownloadPreplannedOfflineMapParameters
  • DownloadPreplannedOfflineMapResult
  • OfflineMapTask
  • PreplannedMapArea

About the data

The Naperville stormwater network map is based on ArcGIS Solutions for Stormwater and provides a realistic depiction of a theoretical stormwater network.

Additional information

PreplannedUpdateMode can be used to set the way the preplanned map area receives updates in several ways:

  • NoUpdates - No updates will be performed. This mode is intended for when a static snapshot of the data is required, and it does not create a replica on the service. This is the mode used for this sample.
  • SyncWithFeatureServices - Changes, including local edits, will be synced directly with the underlying feature services. This is the default update mode.
  • DownloadScheduledUpdates - Scheduled, read-only updates will be downloaded from the online map area and applied to the local mobile geodatabases.

For more information about offline workflows, see Offline maps, scenes, and data in the ArcGIS Developers guide.

Tags

map area, offline, pre-planned, preplanned

Sample Code

DownloadPreplannedMap.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 ArcGISRuntime.Samples.Managers;
using CoreGraphics;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.Tasks.Offline;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using UIKit;

namespace ArcGISRuntimeXamarin.Samples.DownloadPreplannedMap
{
    [Register("DownloadPreplannedMap")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Download preplanned map area",
        category: "Map",
        description: "Take a map offline using a preplanned map area.",
        instructions: "Select a map area from the Preplanned Map Areas list. Tap the button to download the selected area. The download progress will be shown in the Downloads list. When a download is complete, select it to display the offline map in the map view.",
        tags: new[] { "map area", "offline", "pre-planned", "preplanned" })]
    public class DownloadPreplannedMap : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;
        private UITableViewController _tableController;
        private UILabel _helpLabel;
        private UIActivityIndicatorView _activityIndicator;
        private UINavigationController _tableDisplayController;
        private UIBarButtonItem _showOnlineButton;

        private MapAreaViewModel _mapAreaViewModel;

        // ID of a web map with preplanned map areas.
        private const string PortalItemId = "acc027394bc84c2fb04d1ed317aac674";

        // Folder to store the downloaded mobile map packages.
        private string _offlineDataFolder;

        // Task for taking map areas offline.
        private OfflineMapTask _offlineMapTask;

        // Hold onto the original map.
        private Map _originalMap;

        // Hold a list of available map areas.
        private readonly List<PreplannedMapArea> _mapAreas = new List<PreplannedMapArea>();

        // Most recently opened map package.
        private MobileMapPackage _mobileMapPackage;

        public DownloadPreplannedMap()
        {
            Title = "Download a preplanned map area";
        }

        private async void Initialize()
        {
            try
            {
                // The data manager provides a method to get a suitable offline data folder.
                _offlineDataFolder = Path.Combine(DataManager.GetDataFolder(), "SampleData", "DownloadPreplannedMapAreas");

                // If temporary data folder doesn't exists, create it.
                if (!Directory.Exists(_offlineDataFolder))
                {
                    Directory.CreateDirectory(_offlineDataFolder);
                }

                // Create a portal to enable access to the portal item.
                ArcGISPortal portal = await ArcGISPortal.CreateAsync();

                // Create the portal item from the portal item ID.
                PortalItem webMapItem = await PortalItem.CreateAsync(portal, PortalItemId);

                // Show the map.
                _originalMap = new Map(webMapItem);
                _myMapView.Map = _originalMap;

                // Create an offline map task for the web map item.
                _offlineMapTask = await OfflineMapTask.CreateAsync(webMapItem);

                // Find the available preplanned map areas.
                IReadOnlyList<PreplannedMapArea> preplannedAreas = await _offlineMapTask.GetPreplannedMapAreasAsync();

                // Load each item, then add it to the list of areas.
                foreach (PreplannedMapArea area in preplannedAreas)
                {
                    await area.LoadAsync();
                    _mapAreas.Add(area);
                }

                // Configure the table view for showing map areas.
                _mapAreaViewModel = new MapAreaViewModel(_mapAreas);
                _mapAreaViewModel.MapSelected += _mapAreaViewModel_MapSelected;

                _tableController = new UITableViewController(UITableViewStyle.Plain);
                _tableController.TableView.Source = _mapAreaViewModel;

                // Hide the loading indicator.
                _activityIndicator.StopAnimating();
            }
            catch (Exception ex)
            {
                // Something unexpected happened, show the error message.
                Debug.WriteLine(ex);
                new UIAlertView("There was an error", ex.ToString(), (IUIAlertViewDelegate)null, "OK", null).Show();
            }
        }

        private void ShowOnline_Click(object sender, EventArgs e)
        {
            // Show the online map.
            _myMapView.Map = _originalMap;

            // Disable the button.
            _showOnlineButton.Enabled = false;
        }

        private void _mapAreaViewModel_MapSelected(object sender, PreplannedMapArea area)
        {
            // Dismiss the table view.
            _tableDisplayController.DismissViewController(true, null);

            // Download the map area.
            DownloadMapAreaAsync(area);
        }

        private async void DownloadMapAreaAsync(PreplannedMapArea mapArea)
        {
            // Close the current mobile package.
            _mobileMapPackage?.Close();

            // Set up UI for downloading.
            _activityIndicator.StartAnimating();
            _helpLabel.Text = "Downloading map area...";

            // Create folder path where the map package will be downloaded.
            string path = Path.Combine(_offlineDataFolder, mapArea.PortalItem.Title);

            // If the area is already downloaded, open it.
            if (Directory.Exists(path))
            {
                try
                {
                    _mobileMapPackage = await MobileMapPackage.OpenAsync(path);
                    _myMapView.Map = _mobileMapPackage.Maps.First();

                    _helpLabel.Text = "Opened offline area.";
                    _showOnlineButton.Enabled = true;
                    _activityIndicator.StopAnimating();
                    return;
                }
                catch (Exception e)
                {
                    Debug.WriteLine(e);
                    new UIAlertView("Couldn't open offline map area. Proceeding to take area offline.", e.ToString(), (IUIAlertViewDelegate)null, "OK", null).Show();
                }
            }

            // Create download parameters.
            DownloadPreplannedOfflineMapParameters parameters = await _offlineMapTask.CreateDefaultDownloadPreplannedOfflineMapParametersAsync(mapArea);

            // Set the update mode to not receive updates.
            parameters.UpdateMode = PreplannedUpdateMode.NoUpdates;

            // Create the job.
            DownloadPreplannedOfflineMapJob job = _offlineMapTask.DownloadPreplannedOfflineMap(parameters, path);

            // Set up event to update the progress bar while the job is in progress.
            job.ProgressChanged += Job_ProgressChanged;

            try
            {
                // Download the area.
                DownloadPreplannedOfflineMapResult results = await job.GetResultAsync();

                // Set the current mobile map package.
                _mobileMapPackage = results.MobileMapPackage;

                // Handle possible errors and show them to the user.
                if (results.HasErrors)
                {
                    // Accumulate all layer and table errors into a single message.
                    string errors = "";

                    foreach (KeyValuePair<Layer, Exception> layerError in results.LayerErrors)
                    {
                        errors = $"{errors}\n{layerError.Key.Name} {layerError.Value.Message}";
                    }

                    foreach (KeyValuePair<FeatureTable, Exception> tableError in results.TableErrors)
                    {
                        errors = $"{errors}\n{tableError.Key.TableName} {tableError.Value.Message}";
                    }

                    // Show the message.
                    new UIAlertView("Warning!", errors, (IUIAlertViewDelegate)null, "OK", null).Show();
                }

                // Show the downloaded map.
                _myMapView.Map = results.OfflineMap;
            }
            catch (Exception ex)
            {
                // Report any errors.
                Debug.WriteLine(ex);
                new UIAlertView("Downloading map area failed", ex.ToString(), (IUIAlertViewDelegate)null, "OK", null).Show();
            }
            finally
            {
                _activityIndicator.StopAnimating();
                _helpLabel.Text = "Map area offline.";
                _showOnlineButton.Enabled = true;
            }
        }

        private void Job_ProgressChanged(object sender, EventArgs e)
        {
            // Because the event is raised on a background thread, the dispatcher must be used to
            // ensure that UI updates happen on the UI thread.
            InvokeOnMainThread(() =>
            {
                // Update the UI with the progress.
                DownloadPreplannedOfflineMapJob downloadJob = sender as DownloadPreplannedOfflineMapJob;
                _helpLabel.Text = $"Downloading map area... ({downloadJob.Progress}%).";
            });
        }

        private void ShowAreas_Click(object sender, EventArgs e)
        {
            // Show the layer list popover. Note: most behavior is managed by the table view & its source. See MapViewModel.
            _tableDisplayController = new UINavigationController(_tableController);
            UIBarButtonItem closeButton = new UIBarButtonItem("Close", UIBarButtonItemStyle.Plain, (o, ea) => _tableDisplayController.DismissViewController(true, null));
            _tableDisplayController.NavigationBar.Items[0].SetRightBarButtonItem(closeButton, false);
            _tableDisplayController.ModalPresentationStyle = UIModalPresentationStyle.Popover;
            _tableDisplayController.PreferredContentSize = new CGSize(300, 250);
            UIPopoverPresentationController pc = _tableDisplayController.PopoverPresentationController;
            if (pc != null)
            {
                pc.BarButtonItem = (UIBarButtonItem)sender;
                pc.PermittedArrowDirections = UIPopoverArrowDirection.Down;
                pc.Delegate = new ppDelegate();
            }

            PresentViewController(_tableDisplayController, true, null);
        }

        private void DeleteAreas_Click(object sender, EventArgs e)
        {
            try
            {
                // Set up UI for downloading.
                _helpLabel.Text = "Deleting map areas...";
                _activityIndicator.StartAnimating();

                // Reset the map.
                _myMapView.Map = _originalMap;

                // Close the current mobile package.
                _mobileMapPackage?.Close();

                // Delete all data from the temporary data folder.
                Directory.Delete(_offlineDataFolder, true);
                Directory.CreateDirectory(_offlineDataFolder);
            }
            catch (Exception ex)
            {
                // Report the error.
                Debug.WriteLine(ex);
                new UIAlertView("Deleting map area failed", ex.ToString(), (IUIAlertViewDelegate)null, "OK", null).Show();
            }
            finally
            {
                _activityIndicator.StopAnimating();
                _helpLabel.Text = "Deleted offline areas.";
                _showOnlineButton.Enabled = false;
            }
        }

        // Force popover to display on iPhone.
        private class ppDelegate : UIPopoverPresentationControllerDelegate
        {
            public override UIModalPresentationStyle GetAdaptivePresentationStyle(
                UIPresentationController forPresentationController) => UIModalPresentationStyle.None;

            public override UIModalPresentationStyle GetAdaptivePresentationStyle(UIPresentationController controller,
                UITraitCollection traitCollection) => UIModalPresentationStyle.None;
        }

        public override void LoadView()
        {
            // Create the views.
            View = new UIView { BackgroundColor = ApplicationTheme.BackgroundColor };

            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            _showOnlineButton = new UIBarButtonItem("Show online", UIBarButtonItemStyle.Plain, ShowOnline_Click) { Enabled = false };

            UIToolbar toolbar = new UIToolbar();
            toolbar.TranslatesAutoresizingMaskIntoConstraints = false;
            toolbar.Items = new[]
            {
                new UIBarButtonItem("Download", UIBarButtonItemStyle.Plain, ShowAreas_Click),
                new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
                new UIBarButtonItem("Delete all", UIBarButtonItemStyle.Plain, DeleteAreas_Click),
                new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
                _showOnlineButton
            };

            _helpLabel = new UILabel
            {
                Text = "Choose a map area to take offline.",
                AdjustsFontSizeToFitWidth = true,
                TextAlignment = UITextAlignment.Center,
                BackgroundColor = UIColor.FromWhiteAlpha(0, .6f),
                TextColor = UIColor.White,
                Lines = 1,
                TranslatesAutoresizingMaskIntoConstraints = false
            };

            _activityIndicator = new UIActivityIndicatorView(UIActivityIndicatorViewStyle.WhiteLarge);
            _activityIndicator.TranslatesAutoresizingMaskIntoConstraints = false;
            _activityIndicator.HidesWhenStopped = true;
            _activityIndicator.BackgroundColor = UIColor.FromWhiteAlpha(0, .6f);
            _activityIndicator.StartAnimating();

            // Add the views.
            View.AddSubviews(_myMapView, toolbar, _helpLabel, _activityIndicator);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _myMapView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(toolbar.TopAnchor),
                toolbar.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                toolbar.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                toolbar.BottomAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.BottomAnchor),
                _helpLabel.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _helpLabel.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _helpLabel.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _helpLabel.HeightAnchor.ConstraintEqualTo(40),
                _activityIndicator.TopAnchor.ConstraintEqualTo(_helpLabel.BottomAnchor),
                _activityIndicator.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _activityIndicator.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _activityIndicator.BottomAnchor.ConstraintEqualTo(View.BottomAnchor)
            });
        }

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

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

            // Close the current mobile package.
            _mobileMapPackage?.Close();
        }
    }

    internal class MapAreaViewModel : UITableViewSource
    {
        private readonly List<PreplannedMapArea> _maps;
        private const string CellIdentifier = "LayerTableCell";

        public MapAreaViewModel(List<PreplannedMapArea> maps)
        {
            _maps = maps;
        }

        public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
        {
            // Gets a cell for the specified section and row.
            UITableViewCell cell = new UITableViewCell(UITableViewCellStyle.Subtitle, CellIdentifier);
            PreplannedMapArea selectedMap = _maps[indexPath.Row];

            cell.TextLabel.Text = selectedMap.PortalItem.Title;
            try
            {
                NSData imgData = NSData.FromUrl(selectedMap.PortalItem.ThumbnailUri);
                cell.ImageView.Image = new UIImage(imgData);
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex);
            }

            cell.ImageView.ContentMode = UIViewContentMode.ScaleAspectFill;

            return cell;
        }

        public override bool CanEditRow(UITableView tableView, NSIndexPath indexPath)
        {
            return false;
        }

        public override nint RowsInSection(UITableView tableview, nint section)
        {
            return _maps.Count;
        }

        public override nint NumberOfSections(UITableView tableView)
        {
            return 1;
        }

        public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
        {
            PreplannedMapArea selectedMap = _maps[indexPath.Row];

            // Notify subscribers of the new selection.
            RaiseMapAreaSelected(selectedMap);
        }

        // Allow the app to detect when a row is selected.
        // This is an event that can be subscribed to with code like _viewModel.MapAreaSelected += (o, mapArea) => { };
        public delegate void MapAreaSelectedHandler(object sender, PreplannedMapArea area);

        public event MapAreaSelectedHandler MapSelected;

        private void RaiseMapAreaSelected(PreplannedMapArea selectedArea)
        {
            MapSelected?.Invoke(this, selectedArea);
        }
    }
}

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