List KML contents | ArcGIS Maps SDK for Qt

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Sample viewer app

List the contents of a KML file.

screenshot

Use case

KML files can contain a hierarchy of features, including network links to other KML content. A user may wish to traverse through the contents of KML nodes to know what data is contained within each node and, recursively, their children.

How to use the sample

The contents of the KML file are shown in a list of buttons. Select a node to zoom to that node and see its child nodes, if it has any. Not all nodes can be zoomed to (e.g. screen overlays).

How it works

Add the KML file to the scene as a layer.
Explore the root nodes of the KmlDataset recursively to create a view model.

Each node is enabled for display at this step. KML files may include nodes that are turned off by default.

When a node is selected, use the node's KmlViewpoint or Extent to determine a viewpoint and set the SceneView object's viewpoint to it.

Relevant API

KmlContainer
KmlDataset
KmlDocument
KmlFolder
KmlGroundOverlay
KmlLayer
KmlNetworkLink
KmlNode
KmlPhotoOverlay
KmlPlacemark
KmlScreenOverlay
KmlViewpoint

Offline data

To set up the sample's offline data, see the Use offline data in the samples section of the Qt Samples repository overview.

Link	Local Location
Esri KML Sample Data	`<userhome>`/ArcGIS/Runtime/Data/kml/esri_kml_sample_data.kmz

About the data

This is an example KML file meant to demonstrate how the ArcGIS Maps SDK for Native Apps supports several common features.

Sample Code

ListKmlContents.cpp

ListKmlContents.h

ListKmlContents.qml

Use dark colors for code blocksCopy
// [WriteFile Name=ListKmlContents, Category=Layers]
// [Legal]
// Copyright 2020 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

// sample headers
#include "ListKmlContents.h"

// ArcGIS Maps SDK headers
#include "ArcGISTiledElevationSource.h"
#include "Camera.h"
#include "ElevationSourceListModel.h"
#include "Envelope.h"
#include "Error.h"
#include "KmlContainer.h"
#include "KmlDataset.h"
#include "KmlLayer.h"
#include "KmlNetworkLink.h"
#include "KmlNode.h"
#include "KmlNodeListModel.h"
#include "KmlViewpoint.h"
#include "LayerListModel.h"
#include "MapTypes.h"
#include "Point.h"
#include "Scene.h"
#include "SceneQuickView.h"
#include "SpatialReference.h"
#include "Surface.h"
#include "Viewpoint.h"

// Qt headers
#include <QFuture>
#include <QStandardPaths>
#include <QUuid>

// C++ Headers
#include <algorithm>
#include <utility>

using namespace Esri::ArcGISRuntime;

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

#ifdef Q_OS_IOS
    dataPath = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
#else
    dataPath = QStandardPaths::writableLocation(QStandardPaths::HomeLocation);
#endif

    return dataPath;
  }
} // namespace

ListKmlContents::ListKmlContents(QObject* parent /* = nullptr */) :
  QObject(parent),
  m_scene(new Scene(BasemapStyle::ArcGISImagery, this))
{
  // create a new elevation source from Terrain3D REST service
  ArcGISTiledElevationSource* elevationSource =
    new ArcGISTiledElevationSource(QUrl("https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"), this);

  // add the elevation source to the scene to display elevation
  m_scene->baseSurface()->elevationSources()->append(elevationSource);

  const QString filepath = defaultDataPath() + "/ArcGIS/Runtime/Data/kml/esri_kml_sample_data.kmz";

  // create new KML layer
  m_kmlDataset = new KmlDataset(filepath, this);
  KmlLayer* kmlLayer = new KmlLayer(m_kmlDataset, this);
  m_scene->operationalLayers()->append(kmlLayer);

  connect(m_kmlDataset, &KmlDataset::doneLoading, this, [this](const Error& loadError)
  {
    if (!loadError.isEmpty())
    {
      qDebug() << loadError.message() << loadError.additionalMessage();
      return;
    }

    // recursively build tree to display KML contents
    const QList<KmlNode*> nodes = m_kmlDataset->rootNodes();
    buildTree(nodes);

    // if at top node, then display children
    if (!m_kmlNodesList.isEmpty() && m_kmlNodesList[0]->parentNode() == nullptr)
    {
      m_currentNode = m_kmlNodesList[0];
      emit currentNodeChanged();
      emit levelNodeNamesChanged();
    }
  });
}

QString ListKmlContents::getKmlNodeType(KmlNode* node)
{
  if (node == nullptr)
  {
    return "";
  }

  QString type = "";
  switch (node->kmlNodeType())
  {
    case KmlNodeType::KmlDocument:
      type = "KmlDocument";
      break;
    case KmlNodeType::KmlFolder:
      type = "KmlFolder";
      break;
    case KmlNodeType::KmlNetworkLink:
      type = "KmlNetworkLink";
      break;
    case KmlNodeType::KmlPlacemark:
      type = "KmlPlacemark";
      break;
    case KmlNodeType::KmlPhotoOverlay:
      type = "KmlPhotoOverlay";
      break;
    case KmlNodeType::KmlGroundOverlay:
      type = "KmlGroundOverlay";
      break;
    case KmlNodeType::KmlScreenOverlay:
      type = "KmlScreenOverlay";
      break;
    case KmlNodeType::KmlTour:
      type = "KmlTour";
      break;
    default:
      return "";
  }
  return type;
}

// recursively build string to indicate node's ancestors
QStringList ListKmlContents::buildPathLabel(KmlNode* node) const
{
  if (node != nullptr)
  {
    return buildPathLabel(node->parentNode()) << node->name();
  }
  return QStringList{};
}

void ListKmlContents::displayPreviousLevel()
{
  KmlNode* parentNode = m_currentNode->parentNode();
  if (parentNode == nullptr)
  {
    return;
  }

  KmlNode* grandparentNode = parentNode->parentNode();

  if (grandparentNode != nullptr)
  {
    m_currentNode = grandparentNode;
  }
  // if grandparent node is nullptr, then at top of tree
  else
  {
    m_currentNode = parentNode;
  }
  emit currentNodeChanged();
  emit labelTextChanged();
  emit levelNodeNamesChanged();
}

// display selected node on sceneview and show its children
void ListKmlContents::processSelectedNode(const QString& nodeName)
{
  // extract the node's name from the string, formatted "name - nodeType"
  QString extractedNodeName = nodeName;
  if (nodeName.contains(" - "))
  {
    int ind = nodeName.lastIndexOf(" - ");
    extractedNodeName = nodeName.left(ind);
  }

  // find node in the list
  for (KmlNode* node : std::as_const(m_kmlNodesList))
  {
    if (extractedNodeName == node->name())
    {
      // update current node
      m_currentNode = node;
      emit currentNodeChanged();
      emit labelTextChanged();
      emit levelNodeNamesChanged();

      // if displaying end-nodes, change m_currentNode to first end-node for correct behavior of back button
      if (KmlContainer* container = dynamic_cast<KmlContainer*>(m_currentNode))
      {
        if (!hasGrandchildren(container))
        {
          m_currentNode = container->childNodesListModel()->at(0);
          emit currentNodeChanged();
        }
      }

      // If node has viewpoint, set view to that viewpoint. Otherwise, create a viewpoint to encompass node's geometry
      KmlViewpoint nodeViewpoint = node->viewpoint();

      if (nodeViewpoint.isEmpty())
      {
        // if no viewpoint, set view to encompass node's geometry
        const Envelope nodeExtent = node->extent();
        if (nodeExtent.isValid())
        {
          if (nodeExtent.width() == 0 && nodeExtent.height() == 0)
          {
            nodeViewpoint = KmlViewpoint::createLookAtViewpoint(nodeExtent.center(), 0, 45, 1000, KmlAltitudeMode::RelativeToGround);
          }
          else
          {
            nodeViewpoint = KmlViewpoint::createWithViewpoint(Viewpoint(nodeExtent));
          }
        }
      }
      // If nodeViewpoint is still empty, this method is a no-op and will not change the current view
      setSceneViewCameraFromKmlViewpoint(nodeViewpoint);
      break;
    }
  }
}

void ListKmlContents::setSceneViewCameraFromKmlViewpoint(const KmlViewpoint& viewpoint)
{
  if (viewpoint.isEmpty())
  {
    return;
  }

  const Camera camera = [&viewpoint]() -> Camera
  {
    switch (viewpoint.type())
    {
      case KmlViewpointType::LookAt:
        return Camera(viewpoint.location(), viewpoint.range(), viewpoint.heading(), viewpoint.pitch(), viewpoint.roll());
      case KmlViewpointType::Camera:
        return Camera(viewpoint.location(), viewpoint.heading(), viewpoint.pitch(), viewpoint.roll());
      default:
        qWarning("Unexpected KmlViewpointType");
        return Camera();
    }
  }();

  if (!camera.location().isValid())
  {
    qWarning() << "Invalid camera location in KML viewpoint";
    return;
  }

  if (viewpoint.altitudeMode() != KmlAltitudeMode::Absolute)
  {
    // Get elevation at camera location
    m_scene->baseSurface()
      ->applyElevationAsync(viewpoint.location())
      .then(this, [camera, this](const Geometry& locationOnSurface)
    {
      const double deltaElevation = Point(locationOnSurface).z();
      const Camera raisedCamera = camera.elevate(deltaElevation);
      m_sceneView->setViewpointCameraAsync(raisedCamera, 1);
    });
  }
  else
  {
    m_sceneView->setViewpointCameraAsync(camera, 1);
  }
}

// recursively build list of all KML nodes
void ListKmlContents::buildTree(const QList<KmlNode*>& rootNodes)
{
  for (KmlNode* node : std::as_const(rootNodes))
  {
    // some nodes have default visibility set to false
    node->setVisible(true);
    m_kmlNodesList << node;

    if (KmlContainer* container = dynamic_cast<KmlContainer*>(node))
    {
      QList<KmlNode*> childNodes;
      for (KmlNode* childNode : *(container->childNodesListModel()))
      {
        childNodes << childNode;
      }
      if (!childNodes.isEmpty())
      {
        buildTree(childNodes);
      }
    }
    else if (KmlNetworkLink* networkLink = dynamic_cast<KmlNetworkLink*>(node))
    {
      const QList<KmlNode*> childNodes = networkLink->childNodes();
      buildTree(childNodes);
    }
  }
}

ListKmlContents::~ListKmlContents() = default;

void ListKmlContents::init()
{
  // Register classes for QML
  qmlRegisterType<SceneQuickView>("Esri.Samples", 1, 0, "SceneView");
  qmlRegisterType<ListKmlContents>("Esri.Samples", 1, 0, "ListKmlContentsSample");
}

SceneQuickView* ListKmlContents::sceneView() const
{
  return m_sceneView;
}

// Set the view (created in QML)
void ListKmlContents::setSceneView(SceneQuickView* sceneView)
{
  if (!sceneView || sceneView == m_sceneView)
  {
    return;
  }

  m_sceneView = sceneView;
  m_sceneView->setArcGISScene(m_scene);

  emit sceneViewChanged();
}

QStringList ListKmlContents::levelNodeNames()
{
  if (m_currentNode == nullptr)
  {
    return {};
  }

  QStringList nodeNames = {};

  // if node is not a container, m_levelNodeNames will be unchanged
  if (KmlContainer* container = dynamic_cast<KmlContainer*>(m_currentNode))
  {
    // for current level, get names of child nodes
    for (KmlNode* node : *(container->childNodesListModel()))
    {
      QString str = node->name() + " - " + getKmlNodeType(node);

      // if node has children, add ">" to indicate further levels
      if (!node->children().isEmpty())
      {
        str.append(" >");
      }
      nodeNames << str;
    }
    m_levelNodeNames = nodeNames;
  }
  return m_levelNodeNames;
}

bool ListKmlContents::hasGrandchildren(KmlContainer* container) const
{
  return std::any_of(container->childNodesListModel()->begin(), container->childNodesListModel()->end(), [](KmlNode* node)
  {
    if (KmlContainer* container = dynamic_cast<KmlContainer*>(node))
    {
      return !container->children().isEmpty();
    }
    else if (KmlNetworkLink* networkLink = dynamic_cast<KmlNetworkLink*>(node))
    {
      return !networkLink->childNodes().isEmpty();
    }
    return false;
  });
}

QString ListKmlContents::labelText() const
{
  return buildPathLabel(m_currentNode).join(" > ");
}

bool ListKmlContents::isTopLevel() const
{
  return (!m_currentNode || !m_currentNode->parentNode());
}