Feature collection layer (query)

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Create a feature collection layer to show a query result from a service feature table.

screenshot

Use case

Consider a national wireless telecommunications company who wants to improve connectivity within areas of poor coverage. Their cell towers, cell tower radii and state boundaries data are held within service feature tables, which can be queried for states that don't meet a certain threshold of coverage. The query result can be used to create and display a single feature collection layer for analysis of areas requiring improved coverage.

How to use the sample

When launched, this sample displays a map with point features as a feature collection layer. Pan and zoom to explore the map.

How it works

  1. Perform a query using the queryFeatures() method on a ServiceFeatureTable.
  2. Instantiate a FeatureCollectionTable with the result of the query.
  3. Create a FeatureCollection and add the feature collection table to it.
  4. Create a FeatureCollectionLayer from the feature collection.
  5. Add the feature collection layer to the map's operationalLayers list.

Relevant API

  • FeatureCollection
  • FeatureCollectionLayer
  • FeatureCollectionTable
  • FeatureLayer
  • FeatureQueryResult
  • FeatureTable
  • QueryParameters
  • ServiceFeatureTable

About the data

This application utilizes data from the wildfire feature service. It loads at full extent with features indicating wildfire response point features across the world.

Tags

layer, query, search, table

Sample Code

FeatureCollectionLayerQuery.cppFeatureCollectionLayerQuery.cppFeatureCollectionLayerQuery.hFeatureCollectionLayerQuery.qml
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// [WriteFile Name=FeatureCollectionLayerQuery, Category=Layers]
// [Legal]
// Copyright 2017 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 "FeatureCollectionLayerQuery.h"

#include "FeatureCollection.h"
#include "FeatureCollectionLayer.h"
#include "FeatureCollectionTable.h"
#include "Map.h"
#include "MapQuickView.h"
#include "ServiceFeatureTable.h"

#include <QString>

using namespace Esri::ArcGISRuntime;

FeatureCollectionLayerQuery::FeatureCollectionLayerQuery(QQuickItem* parent /* = nullptr */):
  QQuickItem(parent)
{
}

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

bool FeatureCollectionLayerQuery::busy() const
{
  return m_busy;
}

void FeatureCollectionLayerQuery::setBusy(bool val)
{
  if (val == m_busy)
    return;

  m_busy = val;
  emit busyChanged();
}

void FeatureCollectionLayerQuery::componentComplete()
{
  QQuickItem::componentComplete();

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");

  // Create a map using the oceans basemap
  m_map = new Map(BasemapStyle::ArcGISOceans, this);

  // Set map to map view
  m_mapView->setMap(m_map);

  //initialize service feature table to be queried
  m_featureTable = new ServiceFeatureTable(QUrl(QStringLiteral("https://sampleserver6.arcgisonline.com/arcgis/rest/services/Wildfire/FeatureServer/0")), this);

  //create query parameters
  QueryParameters queryParams;

  // 1=1 will give all the features from the table
  queryParams.setWhereClause("1=1");

  connect(m_featureTable, &ServiceFeatureTable::queryFeaturesCompleted, this, [this](QUuid, FeatureQueryResult* featureQueryResult)
  {
    setBusy(false);

    if (!featureQueryResult)
      return;

    //create a feature collection table fromt the query results
    FeatureCollectionTable* featureCollectionTable = new FeatureCollectionTable(featureQueryResult, this);

    //create a feature collection from the above feature collection table
    FeatureCollection* featureCollection = new FeatureCollection(QList<FeatureCollectionTable*> {featureCollectionTable}, this);

    //create a feature collection layer
    FeatureCollectionLayer* featureCollectionLayer = new FeatureCollectionLayer(featureCollection, this);

    //add the layer to the operational layers array
    m_map->operationalLayers()->append(featureCollectionLayer);
  });

  m_featureTable->queryFeatures(queryParams);
  setBusy(true);
}

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