Generate geodatabase

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Generate a local geodatabase from an online feature service.

Generate geodatabase sample

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. When complete, the map will reload with only the layers in the geodatabase, clipped to the extent.

How it works

  1. Create an AGSGeodatabaseSyncTask with the URL of the feature service and load it.
  2. Use AGSGeodatabaseSyncTask.defaultGenerateGeodatabaseParameters(withExtent:completion:) to generate default parameters and specify the extent.
  3. Request a job to generate the geodatabase using AGSGeodatabaseSyncTask.generateJob(with:downloadFileURL:).
  4. Start the job with AGSGenerateGeodatabaseJob.start(statusHandler:completion:).
  5. When the job is done, add all the AGSFeatureLayers from the geodatabase's geodatabaseFeatureTables to the map's operationalLayers.
  6. Lastly, unregister the geodatabase with AGSGeodatabaseSyncTask.unregisterGeodatabase(_:completion:).

Relevant API

  • AGSGenerateGeodatabaseJob
  • AGSGenerateGeodatabaseParameters
  • AGSGeodatabase
  • AGSGeodatabaseSyncTask

Offline data

This sample uses a San Francisco offline basemap tile package.

Tags

disconnected, local geodatabase, offline, sync

Sample Code

GenerateGeodatabaseViewController.swift
                                                                                                                                                                       
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//
// Copyright 2016 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.

import UIKit
import ArcGIS

class GenerateGeodatabaseViewController: UIViewController {
    @IBOutlet var mapView: AGSMapView!
    @IBOutlet var downloadBBI: UIBarButtonItem!
    @IBOutlet var extentView: UIView!

    private var syncTask: AGSGeodatabaseSyncTask = {
        let featureServiceURL = URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Sync/WildfireSync/FeatureServer")!
        return AGSGeodatabaseSyncTask(url: featureServiceURL)
    }()
    private var generatedGeodatabase: AGSGeodatabase?
    // must retain a strong reference to a job while it runs
    private var activeJob: AGSJob?

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the source code button item to the right of navigation bar
        (navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["GenerateGeodatabaseViewController"]

        let tileCache = AGSTileCache(name: "SanFrancisco")
        let localTiledLayer = AGSArcGISTiledLayer(tileCache: tileCache)

        let map = AGSMap(basemap: AGSBasemap(baseLayer: localTiledLayer))
        mapView.map = map

        addFeatureLayers()

        // setup extent view
        extentView.layer.borderColor = UIColor.red.cgColor
        extentView.layer.borderWidth = 3
    }

    func addFeatureLayers() {
        syncTask.load { [weak self] (error) in
            if let error = error {
                print("Could not load feature service \(error)")
            } else {
                guard let self = self,
                    let featureServiceInfo = self.syncTask.featureServiceInfo else {
                    return
                }

                // For each layer in the service, add a layer to the map.
                let featureLayers = featureServiceInfo.layerInfos.enumerated().map { (offset, layerInfo) -> AGSFeatureLayer in
                    let layerURL = self.syncTask.url!.appendingPathComponent(String(offset))
                    let featureTable = AGSServiceFeatureTable(url: layerURL)
                    let featureLayer = AGSFeatureLayer(featureTable: featureTable)
                    featureLayer.name = layerInfo.name
                    featureLayer.opacity = 0.65
                    return featureLayer
                }
                self.mapView.map?.operationalLayers.addObjects(from: featureLayers.reversed())

                // enable download
                self.downloadBBI.isEnabled = true
            }
        }
    }

    func frameToExtent() -> AGSEnvelope {
        let frame = mapView.convert(extentView.frame, from: view)
        let minPoint = mapView.screen(toLocation: frame.origin)
        let maxPoint = mapView.screen(toLocation: CGPoint(x: frame.maxX, y: frame.maxY))
        let extent = AGSEnvelope(min: minPoint, max: maxPoint)
        return extent
    }

    // MARK: - Actions

    @IBAction func downloadAction() {
        // generate default param to contain all layers in the service
        syncTask.defaultGenerateGeodatabaseParameters(withExtent: self.frameToExtent()) { [weak self] (params: AGSGenerateGeodatabaseParameters?, error: Error?) in
            if let params = params,
                let self = self {
                // don't include attachments to minimze the geodatabae size
                params.returnAttachments = false

                // create a unique name for the geodatabase based on current timestamp
                let dateFormatter = ISO8601DateFormatter()

                let documentDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
                let downloadFileURL = documentDirectoryURL
                    .appendingPathComponent(dateFormatter.string(from: Date()))
                    .appendingPathExtension("geodatabase")

                // request a job to generate the geodatabase
                let generateJob = self.syncTask.generateJob(with: params, downloadFileURL: downloadFileURL)
                self.activeJob = generateJob
                // kick off the job
                generateJob.start(
                    statusHandler: { (status: AGSJobStatus) in
                        UIApplication.shared.showProgressHUD(message: status.statusString())
                    },
                    completion: { [weak self] (geodatabase: AGSGeodatabase?, error: Error?) in
                        UIApplication.shared.hideProgressHUD()

                        if let error = error {
                            self?.presentAlert(error: error)
                        } else {
                            self?.generatedGeodatabase = geodatabase
                            self?.displayLayersFromGeodatabase()
                        }

                        self?.activeJob = nil
                    }
                )
            } else {
                print("Could not generate default parameters: \(error!)")
            }
        }
    }

    func displayLayersFromGeodatabase() {
        guard let generatedGeodatabase = generatedGeodatabase else {
            return
        }
        generatedGeodatabase.load { [weak self] (error: Error?) in
            guard let self = self else {
                return
            }

            if let error = error {
                self.presentAlert(error: error)
            } else {
                self.mapView.map?.operationalLayers.removeAllObjects()

                AGSLoadObjects(generatedGeodatabase.geodatabaseFeatureTables) { (success: Bool) in
                    if success {
                        for featureTable in generatedGeodatabase.geodatabaseFeatureTables.reversed() {
                            // check if featureTable has geometry
                            if featureTable.hasGeometry {
                                let featureLayer = AGSFeatureLayer(featureTable: featureTable)
                                self.mapView.map?.operationalLayers.add(featureLayer)
                            }
                        }
                        self.presentAlert(message: "Now showing data from geodatabase")

                        // hide the extent view
                        self.extentView.isHidden = true
                        // disable the download button
                        self.downloadBBI.isEnabled = false
                    }
                    // unregister geodatabase as the sample wont be editing or syncing features
                    self.syncTask.unregisterGeodatabase(generatedGeodatabase)
                }
            }
        }
    }
}

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