Display a WFS layer

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Sample viewer app

Display a layer from a WFS service, requesting only features for the current extent.

screenshot

Use case

WFS is an open standard with functionality similar to ArcGIS feature services. Runtime support for WFS allows you to interoperate with open systems, which are often used in inter-agency efforts, like those for disaster relief.

How to use the sample

Pan and zoom to see features within the current map extent.

How it works

  1. Create a WfsFeatureTable with a URL and table name.
  2. Create a FeatureLayer from the feature table and add it to the map.
  3. Listen for the MapView::navigatingChanged signal to detect when the user has stopped navigating the map.
  4. When the user is finished navigating, use populateFromService to load the table with data for the current visible extent.

Relevant API

  • FeatureLayer
  • MapView::navigatingChanged
  • WfsFeatureTable
  • WfsFeatureTable::populateFromService

About the data

This service shows building footprints for downtown Seattle. For additional information, see the underlying service on ArcGIS Online.

Tags

browse, catalog, feature, interaction cache, layers, OGC, service, web, WFS

Sample Code

DisplayWfsLayer.cppDisplayWfsLayer.cppDisplayWfsLayer.hDisplayWfsLayer.qml
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// [WriteFile Name=DisplayWfsLayer, Category=Layers]
// [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 "DisplayWfsLayer.h"

#include "Map.h"
#include "MapQuickView.h"
#include "WfsFeatureTable.h"
#include "FeatureLayer.h"
#include "QueryParameters.h"
#include "SimpleRenderer.h"
#include "SimpleLineSymbol.h"

using namespace Esri::ArcGISRuntime;

DisplayWfsLayer::DisplayWfsLayer(QObject* parent /* = nullptr */):
  QObject(parent),
  m_map(new Map(BasemapStyle::ArcGISTopographic, this))
{
  // create WFS Feature Table
  m_wfsFeatureTable = new WfsFeatureTable(QUrl("https://dservices2.arcgis.com/ZQgQTuoyBrtmoGdP/arcgis/services/Seattle_Downtown_Features/WFSServer?service=wfs&request=getcapabilities"),
                                          "Seattle_Downtown_Features:Buildings", this);

  // Set feature request mode to manual - only manual is supported at v100.5.
  // In this mode, you must manually populate the table - panning and zooming
  // won't request features automatically.
  m_wfsFeatureTable->setFeatureRequestMode(FeatureRequestMode::ManualCache);

  // populate the feature table once loaded
  connect(m_wfsFeatureTable, &WfsFeatureTable::doneLoading, this, [this](Error e)
  {
    if (e.isEmpty())
      populateWfsFeatureTable();
  });

  // create feature layer from the feature table
  FeatureLayer* featureLayer = new FeatureLayer(m_wfsFeatureTable, this);

  // add a renderer to the layer
  SimpleLineSymbol* sls = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("red"), 3.0f, this);
  SimpleRenderer* sr = new SimpleRenderer(sls, this);
  featureLayer->setRenderer(sr);

  // add the layer to the map
  m_map->operationalLayers()->append(featureLayer);

  // set initial viewpoint
  Envelope env(-122.341581, 47.613758, -122.332662, 47.617207, SpatialReference::wgs84());
  m_map->setInitialViewpoint(Viewpoint(env));
}

DisplayWfsLayer::~DisplayWfsLayer() = default;

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

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

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

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

  connect(m_mapView, &MapQuickView::navigatingChanged, this, [this]()
  {
    if (m_mapView->isNavigating())
      return;

    populateWfsFeatureTable();
  });

  emit mapViewChanged();
}

void DisplayWfsLayer::populateWfsFeatureTable()
{
  if (!m_mapView || !m_wfsFeatureTable)
    return;

  // create query parameters
  QueryParameters params;
  params.setGeometry(m_mapView->visibleArea().extent());
  params.setSpatialRelationship(SpatialRelationship::Intersects);

  // query the service
  constexpr bool clearCache = false;
  const QStringList outFields = {"*"};
  m_wfsFeatureTable->populateFromService(params, clearCache, outFields);
}

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