Generate offline map with local basemap

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Sample viewer app

Use the OfflineMapTask to take a web map offline, but instead of downloading an online basemap, use one which is already on the device.

screenshot

Use case

There are a number of use-cases where you may wish to use a basemap which is already on the device, rather than downloading:

  • You want to limit the total download size.
  • You want to be able to share a single set of basemap files between many offline maps.
  • You want to use a custom basemap (for example authored in ArcGIS Pro) which is not available online.
  • You do not wish to sign into ArcGIS.com in order to download Esri basemaps.

The author of a web map can support the use of basemaps which are already on a device by configuring the web map to specify the name of a suitable basemap file. This could be a basemap which:

  • Has been authored in ArcGIS Pro to make use of your organization's custom data.
  • Is available as a PortalItem which can be downloaded once and re-used many times.

How to use the sample

  1. Click on "Generate Offline Map".
  2. You will be prompted to choose whether you wish to download the online basemap or use the "naperville_imagery.tpkx" basemap which is already on the device.
  3. If you choose to download the online basemap, the offline map will be generated with the same (topographic) basemap as the online web map.
  4. If you choose to use the basemap from the device, the offline map will be generated with the local imagery basemap. The download will be quicker since no tiles are exported or downloaded.
  5. Since the application is not exporting online ArcGIS Online basemaps you will not need to log-in.

How it works

  1. The sample creates a PortalItem object using a web map's ID. This portal item is used to initialize an OfflineMapTask object. When the button is clicked, the sample requests the default parameters for the task, with the selected extent, by calling OfflineMapTask::createDefaultGenerateOfflineMapParameters.
  2. If the user chooses to use the basemap on the device, the GenerateOfflineMapParameters::referenceBasemapDirectory is set to the absolute path of the directory which contains the .tpkx file.
  3. A GenerateOfflineMapJob is created by calling OfflineMapTask::generateOfflineMap passing the parameters and the download location for the offline map.
  4. When the GenerateOfflineMapJob is started it will check whether GenerateOfflineMapParameters::referenceBasemapDirectory has been set. If this property is set, no online basemap will be downloaded and instead, the mobile map will be created with a reference to the .tpkx on the device.

Relevant API

  • GenerateOfflineMapJob
  • GenerateOfflineMapParameters
  • GenerateOfflineMapResult
  • OfflineMapTask

Offline data

Read more about how to set up the sample's offline data here.

Link Local Location
Naperville Imagery Tile Package <userhome>/ArcGIS/Runtime/Data/tpkx/naperville_imagery.tpkx

Tags

basemap, download, local, offline, save, web map

Sample Code

GenerateOfflineMapLocalBasemap.cppGenerateOfflineMapLocalBasemap.cppGenerateOfflineMapLocalBasemap.hDownloadButton.qmlGenerateWindow.qmlGenerateOfflineMapLocalBasemap.qml
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// [WriteFile Name=GenerateOfflineMapLocalBasemap, Category=Maps]
// [Legal]
// 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.
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "GenerateOfflineMapLocalBasemap.h"

#include "Map.h"
#include "MapQuickView.h"
#include "Portal.h"
#include "PortalItem.h"
#include "OfflineMapTask.h"
#include "GeometryEngine.h"
#include "Envelope.h"
#include "Point.h"

#include <QDir>
#include <QTemporaryDir>
#include <QtCore/qglobal.h>

#ifdef Q_OS_IOS
#include <QStandardPaths>
#endif // Q_OS_IOS

using namespace Esri::ArcGISRuntime;

// helper method to get cross platform data path
namespace
{
QString defaultDataPath()
{
  QString dataPath;

#ifdef Q_OS_ANDROID
  dataPath = "/sdcard";
#elif defined Q_OS_IOS
  dataPath = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
#else
  dataPath = QDir::homePath();
#endif

  return dataPath;
}
} // namespace

const QString GenerateOfflineMapLocalBasemap::s_webMapId = QStringLiteral("acc027394bc84c2fb04d1ed317aac674");

GenerateOfflineMapLocalBasemap::GenerateOfflineMapLocalBasemap(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent)
{
}

void GenerateOfflineMapLocalBasemap::init()
{
  // Register the map view for QML
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<GenerateOfflineMapLocalBasemap>("Esri.Samples", 1, 0, "GenerateOfflineMapLocalBasemapSample");
}

void GenerateOfflineMapLocalBasemap::componentComplete()
{
  QQuickItem::componentComplete();

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");

  // Create a Portal Item for use by the Map and OfflineMapTask
  m_portalItem = new PortalItem(webMapId(), this);

  // Create a map from the Portal Item
  m_map = new Map(m_portalItem, this);

  // Update property once map is done loading
  connect(m_map, &Map::doneLoading, this, [this](Error e)
  {
    if (!e.isEmpty())
      return;

    m_mapLoaded = true;
    emit mapLoadedChanged();
  });

  // Set map to map view
  m_mapView->setMap(m_map);

  // Create the OfflineMapTask with the PortalItem
  m_offlineMapTask = new OfflineMapTask(m_portalItem, this);

  // connect to the error signal
  connect(m_offlineMapTask, &OfflineMapTask::errorOccurred, this, [](Error e)
  {
    if (e.isEmpty())
      return;

    qDebug() << e.message() << e.additionalMessage();
  });
}

void GenerateOfflineMapLocalBasemap::generateMapByExtent(double xCorner1, double yCorner1, double xCorner2, double yCorner2)
{
  // create an envelope from the QML rectangle corners
  const Point corner1 = m_mapView->screenToLocation(xCorner1, yCorner1);
  const Point corner2 = m_mapView->screenToLocation(xCorner2, yCorner2);
  const Envelope extent = Envelope(corner1, corner2);
  const Envelope mapExtent = GeometryEngine::project(extent, SpatialReference::webMercator());
  const QString tempPath = m_tempDir.path() + "/OfflineMap.mmpk";
  const QString dataPath = defaultDataPath() + "/ArcGIS/Runtime/Data/tpkx";

  // connect to the signal for when the default parameters are generated
  connect(m_offlineMapTask, &OfflineMapTask::createDefaultGenerateOfflineMapParametersCompleted,
          this, [this, dataPath, tempPath](QUuid, GenerateOfflineMapParameters params)
  {
    // update default parameters to specify use of local basemap
    // this will prevent new tiles from being generated on the server
    // and will reduce generation and download time
    if (m_useLocalBasemap)
    {
      params.setReferenceBasemapDirectory(dataPath);
      // A default reference basemap filename can be specified by the source portal item's advanced offline options.
      params.setReferenceBasemapFilename("naperville_imagery.tpkx");
    }

    // Take the map offline once the parameters are generated
    GenerateOfflineMapJob* generateJob = m_offlineMapTask->generateOfflineMap(params, tempPath);

    // check if there is a valid job
    if (generateJob)
    {
      // connect to the job's status changed signal
      connect(generateJob, &GenerateOfflineMapJob::jobStatusChanged, this, [this, generateJob]()
      {
        // connect to the job's status changed signal to know once it is done
        switch (generateJob->jobStatus()) {
          case JobStatus::Failed:
            emit updateStatus("Generate failed");
            emit hideWindow(5000, false);
            break;
          case JobStatus::NotStarted:
            emit updateStatus("Job not started");
            break;
          case JobStatus::Paused:
            emit updateStatus("Job paused");
            break;
          case JobStatus::Started:
            emit updateStatus("In progress");
            break;
          case JobStatus::Succeeded:
            // show any layer errors
            if (generateJob->result()->hasErrors())
            {
              QString layerErrors = "";
              const QMap<Layer*, Error>& layerErrorsMap = generateJob->result()->layerErrors();
              for (auto it = layerErrorsMap.cbegin(); it != layerErrorsMap.cend(); ++it)
              {
                layerErrors += it.key()->name() + ": " + it.value().message() + "\n";
              }
              emit showLayerErrors(layerErrors);
            }

            // show the map
            emit updateStatus("Complete");
            emit hideWindow(1500, true);
            m_mapView->setMap(generateJob->result()->offlineMap(this));
            break;
          default:
            break;
        }
      });

      // connect to progress changed signal
      connect(generateJob, &GenerateOfflineMapJob::progressChanged, this, [this, generateJob]()
      {
        emit updateProgress(generateJob->progress());
      });

      // connect to the error signal
      connect(generateJob, &GenerateOfflineMapJob::errorOccurred, this, [](Error e)
      {
        if (e.isEmpty())
          return;

        qDebug() << e.message() << e.additionalMessage();
      });

      // start the generate job
      generateJob->start();
    }
    else
    {
      emit updateStatus("Export failed");
      emit hideWindow(5000, false);
    }
  });

  // generate parameters
  m_offlineMapTask->createDefaultGenerateOfflineMapParameters(mapExtent);
}

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