Identify KML features

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Sample viewer app

Show a callout with formatted content for a KML feature.

screenshot

Use case

A user may wish to select a KML feature to view relevant information about it.

How to use the sample

Click a feature to identify it. Feature information will be displayed in a callout.

Note: the KML layer used in this sample contains a screen overlay. The screen overlay contains a legend and the logos for the National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service (NWS). You can't identify the screen overlay.

How it works

  1. Connect to the MouseClicked event on the MapView.
  2. On click:
  • Call identifyLayer(...) passing in the KmlLayer, screen point and tolerance.
  • Await the result of the identify and then get the KmlPlacemark from the result.
  • Create a callout at the calculated map point and populate the callout content with text from the placemark's BalloonContent. NOTE: KML supports defining HTML for balloon content and may need to be converted from HTML to text.
  • Show the callout.

Note: There are several types of KML features. This sample only identifies features of type KmlPlacemark.

Relevant API

  • GeoView::identifyLayer(...)
  • IdentifyLayerResult
  • KmlLayer
  • KmlPlacemark
  • KmlPlacemark::balloonContent()

About the data

This sample shows a forecast for significant weather within the U.S. Regions of severe thunderstorms, flooding, snowfall, and freezing rain are shown. Tap the features to see details.

Additional information

KML features can have rich HTML content, including images.

Tags

Keyhole, KML, KMZ, NOAA, NWS, OGC, weather

Sample Code

IdentifyKmlFeatures.cppIdentifyKmlFeatures.cppIdentifyKmlFeatures.hIdentifyKmlFeatures.qml
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// [WriteFile Name=IdentifyKmlFeatures, 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

#include "IdentifyKmlFeatures.h"

#include "CalloutData.h"
#include "KmlDataset.h"
#include "KmlLayer.h"
#include "KmlPlacemark.h"
#include "Map.h"
#include "MapQuickView.h"

using namespace Esri::ArcGISRuntime;

namespace
{
const QUrl datasetUrl("https://www.wpc.ncep.noaa.gov/kml/noaa_chart/WPC_Day1_SigWx_latest.kml");
}

IdentifyKmlFeatures::IdentifyKmlFeatures(QObject* parent /* = nullptr */):
  QObject(parent),
  m_map(new Map(BasemapStyle::ArcGISDarkGray, this))
{
  // create new KML layer
  KmlDataset* forecastDataset = new KmlDataset(datasetUrl, this);
  m_forecastLayer = new KmlLayer(forecastDataset, this);
  m_map->operationalLayers()->append(m_forecastLayer);
}

IdentifyKmlFeatures::~IdentifyKmlFeatures() = default;

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

MapQuickView* IdentifyKmlFeatures::mapView() const
{
  return m_mapView;
}

// Set the view (created in QML)
void IdentifyKmlFeatures::setMapView(MapQuickView* mapView)
{
  if (!mapView || mapView == m_mapView)
    return;

  m_mapView = mapView;
  m_mapView->setMap(m_map);

  // start zoomed in over the US
  m_mapView->setViewpointGeometry(Envelope(-19195297.778679, 512343.939994, -3620418.579987, 8658913.035426, SpatialReference::webMercator()));

  connect(m_mapView, &MapQuickView::identifyLayerCompleted, this, [this](QUuid, Esri::ArcGISRuntime::IdentifyLayerResult *rawResult)
  {
    auto result = std::unique_ptr<IdentifyLayerResult>(rawResult);

    // if not clicked on KML feature then close callout
    if (result->geoElements().length() < 1)
    {
      m_mapView->calloutData()->setVisible(false);
      return;
    }

    // find the first geoElement that is a KML placemark
    const auto elements = result->geoElements();
    for (GeoElement* geoElement : elements)
    {
      if (KmlPlacemark* placemark = dynamic_cast<KmlPlacemark*>(geoElement))
      {
        // Google Earth only displays the placemarks with description or extended data. To
        // match its behavior, add a description placeholder if the data source is empty
        if (placemark->description().isEmpty())
          placemark->setDescription("Weather condition");

        m_calloutText = placemark->balloonContent();
        m_mapView->calloutData()->setLocation(m_clickedPoint);
        m_mapView->calloutData()->setVisible(true);

        emit calloutDataChanged();
        emit calloutTextChanged();
        return;
      }
    }
  });

  // identify clicked features
  connect(m_mapView, &MapQuickView::mouseClicked, this, [this](QMouseEvent& e)
  {
    m_clickedPoint = m_mapView->screenToLocation(e.x(), e.y());
    m_mapView->identifyLayer(m_forecastLayer, e.x(), e.y(), 15, false);
  });

  emit mapViewChanged();
}

CalloutData* IdentifyKmlFeatures::calloutData() const
{
  return m_calloutData;
}

QString IdentifyKmlFeatures::calloutText() const
{
  return m_calloutText;
}

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