Generate geodatabase

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Generate a local geodatabase from an online feature service.

Image of generate geodatabase

Use case

Generating geodatabases is the first step toward taking a feature service offline. It allows you to save features locally for offline display.

How to use the sample

Zoom to any extent. Then tap the generate button to generate a geodatabase of features from a feature service filtered to the current extent. A red outline will show the extent used. The job's progress is shown while the geodatabase is generated.

How it works

  1. Create a GeodatabaseSyncTask with the URL of the feature service and load it.
  2. Create GenerateGeodatabaseParameters specifying the extent and whether to include attachments.
  3. Create a GenerateGeodatabaseJob with geodatabaseSyncTask.GenerateGeodatabaseAsync(parameters, downloadPath). Start the job with job.Start().
  4. When the job is done, job.GetResultAsync() will return the geodatabase. Inside the geodatabase are feature tables which can be used to add feature layers to the map.
  5. Call syncTask.UnregisterGeodatabaseAsync(geodatabase) after generation when you're not planning on syncing changes to the service.

Relevant API

  • GenerateGeodatabaseJob
  • GenerateGeodatabaseParameters
  • Geodatabase
  • GeodatabaseSyncTask

Tags

disconnected, local geodatabase, offline, sync

Sample Code

GenerateGeodatabase.cs
                                                                                                                                                                                                                                                                                                                                                                                       
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// 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.IO;
using System.Linq;
using System.Threading.Tasks;
using ArcGISRuntime.Samples.Managers;
using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.Tasks;
using Esri.ArcGISRuntime.Tasks.Offline;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.GenerateGeodatabase
{
    [Register("GenerateGeodatabase")]
    [ArcGISRuntime.Samples.Shared.Attributes.OfflineData("e4a398afe9a945f3b0f4dca1e4faccb5")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Generate geodatabase",
        category: "Data",
        description: "Generate a local geodatabase from an online feature service.",
        instructions: "Zoom to any extent. Then tap the generate button to generate a geodatabase of features from a feature service filtered to the current extent. A red outline will show the extent used. The job's progress is shown while the geodatabase is generated.",
        tags: new[] { "disconnected", "local geodatabase", "offline", "sync" })]
    public class GenerateGeodatabase : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;
        private UIProgressView _progressBar;
        private UIBarButtonItem _generateButton;

        // URL for a feature service that supports geodatabase generation.
        private readonly Uri _featureServiceUri = new Uri("https://sampleserver6.arcgisonline.com/arcgis/rest/services/Sync/WildfireSync/FeatureServer");

        // Path to the geodatabase file on disk.
        private string _gdbPath;

        // Task to be used for generating the geodatabase.
        private GeodatabaseSyncTask _gdbSyncTask;

        // Job used to generate the geodatabase.
        private GenerateGeodatabaseJob _generateGdbJob;

        public GenerateGeodatabase()
        {
            Title = "Generate geodatabase";
        }

        private async void Initialize()
        {
            try
            {
                // Create a tile cache and load it with the SanFrancisco streets tpk.
                TileCache tileCache = new TileCache(DataManager.GetDataFolder("e4a398afe9a945f3b0f4dca1e4faccb5", "SanFrancisco.tpkx"));

                // Create the corresponding layer based on the tile cache.
                ArcGISTiledLayer tileLayer = new ArcGISTiledLayer(tileCache);

                // Create the basemap based on the tile cache.
                Basemap sfBasemap = new Basemap(tileLayer);

                // Create the map with the tile-based basemap.
                Map myMap = new Map(sfBasemap);

                // Assign the map to the MapView.
                _myMapView.Map = myMap;

                // Create a new symbol for the extent graphic.
                SimpleLineSymbol lineSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Red, 2);

                // Create graphics overlay for the extent graphic and apply a renderer.
                GraphicsOverlay extentOverlay = new GraphicsOverlay
                {
                    Renderer = new SimpleRenderer(lineSymbol)
                };

                // Add graphics overlay to the map view.
                _myMapView.GraphicsOverlays.Add(extentOverlay);

                // Create a task for generating a geodatabase (GeodatabaseSyncTask).
                _gdbSyncTask = await GeodatabaseSyncTask.CreateAsync(_featureServiceUri);

                // Add all graphics from the service to the map.
                foreach (IdInfo layer in _gdbSyncTask.ServiceInfo.LayerInfos)
                {
                    // Create the ServiceFeatureTable for this particular layer.
                    ServiceFeatureTable onlineTable = new ServiceFeatureTable(new Uri(_featureServiceUri + "/" + layer.Id));

                    // Wait for the table to load.
                    await onlineTable.LoadAsync();

                    // Add the layer to the map's operational layers if load succeeds.
                    if (onlineTable.LoadStatus == Esri.ArcGISRuntime.LoadStatus.Loaded)
                    {
                        myMap.OperationalLayers.Add(new FeatureLayer(onlineTable));
                    }
                }

                // Update the graphic - needed in case the user decides not to interact before pressing the button.
                UpdateMapExtent();

                // Enable the generate button now that the sample is ready.
                _generateButton.Enabled = true;
            }
            catch (Exception ex)
            {
                ShowStatusMessage(ex.ToString());
            }
        }

        private void UpdateMapExtent()
        {
            // Get the new viewpoint.
            Viewpoint myViewPoint = _myMapView?.GetCurrentViewpoint(ViewpointType.BoundingGeometry);

            // Get the updated extent for the new viewpoint.
            Envelope extent = myViewPoint?.TargetGeometry as Envelope;

            // Return if extent is null.
            if (extent == null)
            {
                return;
            }

            // Create an envelope that is a bit smaller than the extent.
            EnvelopeBuilder envelopeBldr = new EnvelopeBuilder(extent);
            envelopeBldr.Expand(0.70);

            // Get the (only) graphics overlay in the map view.
            GraphicsOverlay extentOverlay = _myMapView.GraphicsOverlays.FirstOrDefault();

            // Return if the extent overlay is null.
            if (extentOverlay == null)
            {
                return;
            }

            // Get the extent graphic.
            Graphic extentGraphic = extentOverlay.Graphics.FirstOrDefault();

            // Create the extent graphic and add it to the overlay if it doesn't exist.
            if (extentGraphic == null)
            {
                extentGraphic = new Graphic(envelopeBldr.ToGeometry());
                extentOverlay.Graphics.Add(extentGraphic);
            }
            else
            {
                // Otherwise, update the graphic's geometry.
                extentGraphic.Geometry = envelopeBldr.ToGeometry();
            }
        }

        private async Task StartGeodatabaseGeneration()
        {
            // Update geodatabase path.
            _gdbPath = $"{Path.GetTempFileName()}.geodatabase";

            // Create a task for generating a geodatabase (GeodatabaseSyncTask).
            _gdbSyncTask = await GeodatabaseSyncTask.CreateAsync(_featureServiceUri);

            // Get the current extent of the red preview box.
            Envelope extent = _myMapView.GraphicsOverlays.First().Graphics.First().Geometry as Envelope;

            // Get the default parameters for the generate geodatabase task.
            GenerateGeodatabaseParameters generateParams = await _gdbSyncTask.CreateDefaultGenerateGeodatabaseParametersAsync(extent);

            // Create a generate geodatabase job.
            _generateGdbJob = _gdbSyncTask.GenerateGeodatabase(generateParams, _gdbPath);

            // Handle the progress changed event (to show progress bar).
            _generateGdbJob.ProgressChanged += GenerateGdbJob_ProgressChanged;

            // Start the job.
            _generateGdbJob.Start();

            // Get the result.
            Geodatabase resultGdb = await _generateGdbJob.GetResultAsync();

            // Do the rest of the work.
            await HandleGenerationStatusChange(_generateGdbJob, resultGdb);
        }

        private void GenerateGdbJob_ProgressChanged(object sender, EventArgs e) => UpdateProgressBar();

        private async Task HandleGenerationStatusChange(GenerateGeodatabaseJob job, Geodatabase resultGdb)
        {
            switch (job.Status)
            {
                // If the job completed successfully, add the geodatabase data to the map.
                case JobStatus.Succeeded:
                    // Clear out the existing layers.
                    _myMapView.Map.OperationalLayers.Clear();

                    // Loop through all feature tables in the geodatabase and add a new layer to the map.
                    foreach (GeodatabaseFeatureTable table in resultGdb.GeodatabaseFeatureTables)
                    {
                        // Create a new feature layer for the table.
                        FeatureLayer layer = new FeatureLayer(table);

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

                    // Best practice is to unregister the geodatabase.
                    await _gdbSyncTask.UnregisterGeodatabaseAsync(resultGdb);

                    // Tell the user that the geodatabase was unregistered.
                    ShowStatusMessage("Since no edits will be made, the local geodatabase has been unregistered per best practice.");

                    // Re-enable the generate button.
                    _generateButton.Enabled = true;
                    break;
                // See if the job failed.
                case JobStatus.Failed:
                    // Create a message to show the user.
                    string message = "Generate geodatabase job failed";

                    // Show an error message (if there is one).
                    if (job.Error != null)
                    {
                        message += ": " + job.Error.Message;
                    }
                    else
                    {
                        // If no error, show messages from the job.
                        IEnumerable<string> m = from msg in job.Messages select msg.Message;
                        message += ": " + string.Join("\n", m);
                    }

                    ShowStatusMessage(message);

                    // Re-enable the generate button.
                    _generateButton.Enabled = true;
                    break;
            }
        }

        private void ShowStatusMessage(string message)
        {
            // Display the message to the user.
            UIAlertView alertView = new UIAlertView("Alert", message, (IUIAlertViewDelegate) null, "OK", null);
            alertView.Show();
        }

        private async void GenerateButton_Clicked(object sender, EventArgs e)
        {
            // Fix the extent of the graphic.
            _myMapView.ViewpointChanged -= MapViewExtentChanged;

            try
            {
                // Disable the generate button.
                _generateButton.Enabled = false;

                // Call the geodatabase generation method.
                await StartGeodatabaseGeneration();
            }
            catch (TaskCanceledException)
            {
                ShowStatusMessage("Geodatabase generation cancelled.");
            }
            catch (Exception ex)
            {
                ShowStatusMessage(ex.ToString());
            }
        }

        private void MapViewExtentChanged(object sender, EventArgs e)
        {
            // Call the map extent update method.
            UpdateMapExtent();
        }

        private void UpdateProgressBar()
        {
            // Needed because this could be called from a non-UI thread.
            InvokeOnMainThread(() =>
            {
                // Update the progress bar value.
                _progressBar.Progress = _generateGdbJob.Progress / 100.0f;
            });
        }

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

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

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

            _generateButton = new UIBarButtonItem();
            _generateButton.Title = "Generate geodatabase";
            _generateButton.Enabled = false;

            UIToolbar toolbar = new UIToolbar();
            toolbar.TranslatesAutoresizingMaskIntoConstraints = false;
            toolbar.Items = new[]
            {
                new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
                _generateButton,
                new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace)
            };

            _progressBar = new UIProgressView();
            _progressBar.TranslatesAutoresizingMaskIntoConstraints = false;

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

            // 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.BottomAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.BottomAnchor),
                toolbar.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                toolbar.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),

                _progressBar.TopAnchor.ConstraintEqualTo(_myMapView.TopAnchor),
                _progressBar.HeightAnchor.ConstraintEqualTo(8),
                _progressBar.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _progressBar.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor)
            });
        }

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

            // Subscribe to events.
            _myMapView.ViewpointChanged += MapViewExtentChanged;
            _generateButton.Clicked += GenerateButton_Clicked;
        }

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

            // Unsubscribe from events, per best practice.
            if (_generateGdbJob != null)
            {
                _generateGdbJob.Cancel();
                _generateGdbJob.ProgressChanged -= GenerateGdbJob_ProgressChanged;
            }

            _myMapView.ViewpointChanged -= MapViewExtentChanged;
            _generateButton.Clicked -= GenerateButton_Clicked;
        }
    }
}

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