Display OGC API Feature Collection

View inQMLC++
View on GitHub
Sample viewer app

This sample demonstrates how to display an OGC API feature collection and query features while navigating the map view.

screenshot

Use case

When panning the map view, it is necessary to query the OGC API feature table to obtain additional features within the new visible extent.

How to use the sample

Pan the map and observe how new features are loaded from the OGC API feature service.

How it works

  1. Create an OgcFeatureCollectionTable object using a URL to an OGC API feature service and a collection ID.

  2. Set the feature table's FeatureRequestMode to ManualCache so features requested from the server are cached locally.

  3. Create a FeatureLayer using the feature table and add it to the Map's operationalLayers.

  4. Every time the map view navigation completes:

    i. Create QueryParameters

    ii. Set the parameter's Geometry to the current extent of the map view.

    iii. Set the parameter's SpatialRelationship to Intersects.

    iv. Set the MaxFeatures property to 5000 (some services have a low default value for maximum features).

    v. Call OgcFeatureCollectionTable::PopulateFromService() using the query parameters from the previous steps.

Relevant API

  • OgcFeatureCollectionTable
  • QueryParameters

Additional information

See the OGC API website for more information on the OGC API family of standards.

Tags

feature, feature layer, feature table, OGC, OGC API, service, table, web

Sample Code

DisplayOgcApiFeatureCollection.cppDisplayOgcApiFeatureCollection.cppDisplayOgcApiFeatureCollection.hDisplayOgcApiFeatureCollection.qml
Use dark colors for code blocksCopy
                                                                                                  
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
// [WriteFile Name=DisplayOgcApiFeatureCollection, Category=Layers]
// [Legal]
// Copyright 2021 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 "DisplayOgcApiFeatureCollection.h"

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

using namespace Esri::ArcGISRuntime;

DisplayOgcApiFeatureCollection::DisplayOgcApiFeatureCollection(QObject* parent /* = nullptr */):
  QObject(parent),
  m_map(new Map(BasemapStyle::ArcGISTopographic, this))
{
  const QUrl serviceUrl = QUrl("https://demo.ldproxy.net/daraa");
  const QString collectionId = "TransportationGroundCrv";
  m_ogcFeatureCollectionTable = new OgcFeatureCollectionTable(serviceUrl, collectionId, this);

  // FeatureRequestMode::ManualCache specifies that features from the server will be stored locally for display and querying
  // In this mode, ServiceFeatureTable::populateFromService() must be called to populate the local cache
  m_ogcFeatureCollectionTable->setFeatureRequestMode(FeatureRequestMode::ManualCache);

  // m_ogcFeatureCollectionTable->load() will be automatically called when added to a FeatureLayer
  m_featureLayer = new FeatureLayer(m_ogcFeatureCollectionTable, this);
  m_featureLayer->setRenderer(new SimpleRenderer(new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, Qt::blue, 3, this), this));
  m_map->operationalLayers()->append(m_featureLayer);
}

DisplayOgcApiFeatureCollection::~DisplayOgcApiFeatureCollection() = default;

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

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

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

  m_mapView = mapView;
  m_mapView->setMap(m_map);
  m_mapView->setViewpoint(Viewpoint(32.62, 36.10, 20'000));

  createQueryConnection();

  emit mapViewChanged();
}

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

    QueryParameters queryParameters = QueryParameters();
    // Set the query area to what is currently visible in the map view
    queryParameters.setGeometry(m_mapView->currentViewpoint(ViewpointType::BoundingGeometry).targetGeometry());
    // SpatialRelationship::Intersects will return all features that are within and crossing the perimiter of the input geometry
    queryParameters.setSpatialRelationship(SpatialRelationship::Intersects);
    // Some services have low default values for max features returned
    queryParameters.setMaxFeatures(5000);

    // Populate the feature collection table with features that match the parameters, cache them locally, and store all table fields
    m_ogcFeatureCollectionTable->populateFromService(queryParameters, false, {});
  });
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.