Generate offline map

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Sample viewer app

Take a web map offline.

screenshot

Use case

Taking a web map offline allows users continued productivity when their network connectivity is poor or nonexistent. For example, by taking a map offline, a field worker inspecting utility lines in remote areas could still access a feature's location and attribute information.

How to use the sample

When the map loads, zoom to the extent you want to take offline. The red border shows the extent that will be downloaded. Tap the "Generate offline map" button to start the offline map job. The progress view will show the job's progress. When complete, the offline map will replace the online map in the map view.

How it works

  1. Create a Map with a Portal item pointing to the web map.
  2. Create GenerateOfflineMapParameters specifying the download area geometry, minimum scale, and maximum scale.
  3. Create an OfflineMapTask with the map.
  4. Create the OfflineMapJob with OfflineMapTask::generateOfflineMap(params, downloadDirectoryPath) and start it with OfflineMapJob::start().
  5. When the job is done, get the offline map with OfflineMapJob::result()::offlineMap().

Relevant API

  • GenerateOfflineMapJob
  • GenerateOfflineMapParameters
  • GenerateOfflineMapResult
  • OfflineMapTask
  • Portal

About the data

The map used in this sample shows the stormwater network within Naperville, IL, USA, with cartography designed for web and mobile devices with offline support.

Additional information

The creation of the offline map can be fine-tuned using parameter overrides for feature layers, or by using local basemaps. For examples on these, please consult the samples, "Generate Offline Map (Overrides)" and "Generate offline map with local basemap".

Tags

download, offline, save, web map

Sample Code

GenerateOfflineMap.cppGenerateOfflineMap.cppGenerateOfflineMap.hDownloadButton.qmlGenerateWindow.qmlGenerateOfflineMap.qml
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// [WriteFile Name=GenerateOfflineMap, Category=Maps]
// [Legal]
// Copyright 2017 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 "GenerateOfflineMap.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"

using namespace Esri::ArcGISRuntime;

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

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

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

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

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

  // Create a Portal Item for use by the Map and OfflineMapTask
  bool loginRequired = false;
  Portal* portal = new Portal(loginRequired, this);
  m_portalItem = new PortalItem(portal, 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 GenerateOfflineMap::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());

  // connect to the signal for when the default parameters are generated
  connect(m_offlineMapTask, &OfflineMapTask::createDefaultGenerateOfflineMapParametersCompleted,
          this, [this](QUuid, const GenerateOfflineMapParameters& params)
  {
    // Take the map offline once the parameters are generated
    GenerateOfflineMapJob* generateJob = m_offlineMapTask->generateOfflineMap(params, m_tempPath.path() + "/offlinemap");

    // check if there is a valid job
    if (generateJob)
    {
      // connect to the job's status changed signal
      connect(generateJob, &GenerateOfflineMapJob::statusChanged, this, [this, generateJob](JobStatus jobStatus)
      {
        // connect to the job's status changed signal to know once it is done
        switch (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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