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 Extent to determine a viewpoint and set the SceneView object's viewpoint to it.
Relevant API

KmlContainer
KmlDataset
KmlDocument
KmlFolder
KmlGroundOverlay
KmlLayer
KmlNetworkLink
KmlNode
KmlPlacemark
KmlScreenOverlay
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 test data	`<userhome>`/ArcGIS/Runtime/Data/kml/esri_test_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"

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

// STL headers
#include <algorithm>

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_test_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 auto nodes = m_kmlDataset->rootNodes();
    for (KmlNode* node : nodes)
    {
      m_kmlNodesList << node;
      buildTree(node);
    }

    // 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();
  else
    return QStringList {};
}

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

  KmlNode* grandparentNode = parentNode->parentNode();

  if (grandparentNode != nullptr)
  {
    m_currentNode = grandparentNode;
    emit currentNodeChanged();
    emit labelTextChanged();
    emit levelNodeNamesChanged();
  }
  // 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();

      m_viewpoint = Viewpoint();
      getViewpointFromKmlViewpoint(node);
      if (m_needsAltitudeFixed)
      {
        getAltitudeAdjustedViewpoint(node);
      }
      else
      {
        if (!m_viewpoint.isEmpty() && !m_viewpoint.targetGeometry().isEmpty())
          m_sceneView->setViewpointAsync(m_viewpoint);
      }

      // reset m_lastLevel before levelNodeNames() is called
      emit levelNodeNamesChanged();

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

void ListKmlContents::getViewpointFromKmlViewpoint(KmlNode* node)
{
  const KmlViewpoint kmlViewpoint = node->viewpoint();

  if (!kmlViewpoint.isEmpty())
  {
    // altitude adjustment is needed for all but Absolute altitude mode
    m_needsAltitudeFixed = (kmlViewpoint.altitudeMode() != KmlAltitudeMode::Absolute);

    switch (kmlViewpoint.type())
    {
    case KmlViewpointType::LookAt:
      m_viewpoint = Viewpoint(kmlViewpoint.location(), Camera(kmlViewpoint.location(), kmlViewpoint.range(),
                                                              kmlViewpoint.heading(), kmlViewpoint.pitch(), kmlViewpoint.roll()));
      return;
    case KmlViewpointType::Camera:
      m_viewpoint = Viewpoint(kmlViewpoint.location(), Camera(kmlViewpoint.location(),
                                                              kmlViewpoint.heading(), kmlViewpoint.pitch(), kmlViewpoint.roll()));
      return;
    default:
      qWarning("Unexpected KmlViewpointType");
      return;
    }
  }

  // if viewpoint was empty, then use node's extent
  const Envelope nodeExtent = node->extent();
  if (nodeExtent.isValid() && !nodeExtent.isEmpty())
  {
    // when no altitude is specified, assume elevation needs to be adjusted
    m_needsAltitudeFixed = true;

    if (nodeExtent.width() == 0 && nodeExtent.height() == 0)
    {
      // default values: distance = 1000m, pitch = 45 degrees
      m_viewpoint = Viewpoint(nodeExtent);
      m_sceneView->setViewpointCameraAndWait(Camera(nodeExtent.center(), 1000, 0, 45, 0));
      return;
    }
    else
    {
      // add padding to extent
      double bufferDistance = qMax(nodeExtent.width(), nodeExtent.height()) / 20;
      Envelope bufferedExtent = Envelope(nodeExtent.xMin() - bufferDistance, nodeExtent.yMin() - bufferDistance,
                                         nodeExtent.xMax() + bufferDistance, nodeExtent.yMax() + bufferDistance,
                                         nodeExtent.zMin() - bufferDistance, nodeExtent.zMax() + bufferDistance,
                                         SpatialReference::wgs84());
      m_viewpoint = Viewpoint(bufferedExtent);
    }
  }
  else
  {
    // can't show viewpoint
    m_needsAltitudeFixed = false;
    m_viewpoint = Viewpoint();
  }
}

void ListKmlContents::getAltitudeAdjustedViewpoint(KmlNode* node)
{
  // assume altitude mode is clamp-to-ground if not specified
  KmlAltitudeMode altMode = KmlAltitudeMode::ClampToGround;
  KmlViewpoint kmlViewpoint = node->viewpoint();

  if (!kmlViewpoint.isEmpty())
  {
    altMode = kmlViewpoint.altitudeMode();
  }

  // if altitude mode is Absolute, viewpoint doesn't need adjustment
  if (altMode == KmlAltitudeMode::Absolute)
  {
    m_sceneView->setViewpointAsync(m_viewpoint);
    return;
  }

  const Envelope lookAtExtent = geometry_cast<Envelope>(m_viewpoint.targetGeometry());
  const Point lookAtPoint = geometry_cast<Point>(m_viewpoint.targetGeometry());

  if (lookAtExtent.isValid())
  {
    m_scene->baseSurface()->elevationAsync(lookAtExtent.center()).then(this, [this](double elevation)
    {
      onLocationToElevationCompleted_(elevation);
    });
  }
  else if (lookAtPoint.isValid())
  {
    m_scene->baseSurface()->elevationAsync(lookAtPoint).then(this, [this](double elevation)
    {
      onLocationToElevationCompleted_(elevation);
    });
  }
}

// recursively build list of all KML nodes
void ListKmlContents::buildTree(KmlNode* parentNode)
{
  auto addNode = [this](KmlNode* node)
  {
    // some nodes have default visibility set to false
    node->setVisible(true);

    m_kmlNodesList << node;
    buildTree(node);
  };

  if (KmlContainer* container = dynamic_cast<KmlContainer*>(parentNode))
  {
    const KmlNodeListModel& childNodes = *container->childNodesListModel();
    std::for_each(std::begin(childNodes), std::end(childNodes), addNode);
  }
  else if (KmlNetworkLink* networkLink = dynamic_cast<KmlNetworkLink*>(parentNode))
  {
    const QList<KmlNode*> childNodes = networkLink->childNodes();
    std::for_each(std::begin(childNodes), std::end(childNodes), addNode);
  }
}

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();
}

void ListKmlContents::onLocationToElevationCompleted_(double elevation)
{
  // assume altitude mode is clamp-to-ground if not specified
  KmlAltitudeMode altMode = KmlAltitudeMode::ClampToGround;
  KmlViewpoint kmlViewpoint = m_currentNode->viewpoint();

  if (!kmlViewpoint.isEmpty())
  {
    altMode = kmlViewpoint.altitudeMode();
  }
  // if altitude mode is Absolute, viewpoint doesn't need adjustment
  if (altMode == KmlAltitudeMode::Absolute)
    return;

  const Envelope lookAtExtent = geometry_cast<Envelope>(m_viewpoint.targetGeometry());
  const Point lookAtPoint = geometry_cast<Point>(m_viewpoint.targetGeometry());

  if (lookAtExtent.isValid())
  {
    Envelope  target;
    if (altMode == KmlAltitudeMode::ClampToGround)
    {
      // if depth of extent is 0, add 100m to the elevation to get zMax
      if (lookAtExtent.depth() == 0)
      {
        target = Envelope(lookAtExtent.xMin(), lookAtExtent.yMin(),
                          lookAtExtent.xMax(), lookAtExtent.yMax(),
                          elevation, elevation + 100,
                          lookAtExtent.spatialReference());
      }
      else
      {
        target = Envelope(lookAtExtent.xMin(), lookAtExtent.yMin(),
                          lookAtExtent.xMax(), lookAtExtent.yMax(),
                          // set the camera slightly above the placemark by adding one meter
                          elevation, lookAtExtent.depth() + elevation + 1,
                          lookAtExtent.spatialReference());
      }
    }
    else
    {
      target = Envelope(lookAtExtent.xMin(), lookAtExtent.yMin(),
                        lookAtExtent.xMax(), lookAtExtent.yMax(),
                        lookAtExtent.zMin() + elevation, lookAtExtent.zMax() + elevation,
                        lookAtExtent.spatialReference());
    }

    // if node has viewpoint specified, return adjusted geometry with adjusted camera
    if (!kmlViewpoint.isEmpty())
    {
      m_sceneView->setViewpointCameraAndWait(m_viewpoint.camera().elevate(elevation));
      m_viewpoint = Viewpoint(target);
      m_sceneView->setViewpointAsync(m_viewpoint);
      return;
    }
    else
    {
      m_viewpoint = Viewpoint(target);
      m_sceneView->setViewpointAsync(m_viewpoint);
      return;
    }
  }
  else if (lookAtPoint.isValid())
  {
    Point target;
    if (altMode == KmlAltitudeMode::ClampToGround)
    {
      target = Point(lookAtPoint.x(), lookAtPoint.y(), elevation, lookAtPoint.spatialReference());
    }
    else
    {
      target = Point(lookAtPoint.x(), lookAtPoint.y(), lookAtPoint.z() + elevation, lookAtPoint.spatialReference());
    }

    // set the viewpoint using the adjusted target
    if (!kmlViewpoint.isEmpty())
    {
      m_sceneView->setViewpointCameraAndWait(m_viewpoint.camera().elevate(elevation));
      m_viewpoint = Viewpoint(target);
      m_sceneView->setViewpointAsync(m_viewpoint);
      return;
    }
    else
    {
      // use default values to set camera: distance = 1000m, pitch = 45 degrees
      m_viewpoint = Viewpoint(target);
      m_sceneView->setViewpointAsync(m_viewpoint);
      m_sceneView->setViewpointCameraAndWait(Camera(target, 1000, 0, 45, 0));
      return;
    }
  }
}

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::noGrandchildren(KmlNode *currentNode) const
{
  bool hasNoGrandchildren = false;

  if (KmlContainer* container = dynamic_cast<KmlContainer*>(currentNode))
  {
    hasNoGrandchildren = true;

    // for current level, get names of child nodes
    for (KmlNode* node: *(container->childNodesListModel()))
    {
      // if node has children, add ">" to indicate further levels
      if (!node->children().isEmpty())
      {
        hasNoGrandchildren = false;
      }
    }
  }

  return hasNoGrandchildren;
}

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

bool ListKmlContents::isTopLevel() const
{
  if (m_currentNode == nullptr)
    return true;
  else if (m_currentNode->parentNode() == nullptr)
    return true;
  else if (m_currentNode->name() == "")
    return true;
  else
    return false;
}