Query map image sublayer

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Find features in a sublayer based on attributes and location.

screenshot

Use case

Sublayers of an ArcGISMapImageLayer may expose a ServiceFeatureTable through a table property. This allows you to perform the same queries available when working with a table from a FeatureLayer: attribute query, spatial query, statistics query, query for related features, etc. An image layer with a sublayer of counties can be queried by population to only show those above a minimum population.

How to use the sample

Specify a minimum population in the input field (values under 1810000 will produce a selection in all layers) and click the query button to query the sublayers in the current view extent. After a short time, the results for each sublayer will appear as graphics.

How it works

  1. Create an ArcGISMapImageLayer object using the URL of an image service.
  2. After loading the layer, get the sublayer you want to query with (ArcGISMapImageSublayer) layer::subLayers()::at(index).
  3. Load the sublayer, and then get its ServiceFeatureTable with sublayer::table().
  4. Create QueryParameters. You can use queryParameters::setWhereClause(sqlQueryString) to query against a table attribute and/or set queryParameters::setGeometry(extent) to limit the results to an area of the map.
  5. Call sublayerTable::queryFeatures(queryParameters) to get a FeatureQueryResult with features matching the query. The result is an iterable of features.

Relevant API

  • ServiceFeatureTable
  • ArcGISMapImageLayer
  • ArcGISMapImageLayer::loadTablesAndLayers
  • ArcGISMapImageSublayer
  • ArcGISMapImageSublayer::table
  • QueryParameters

About the data

The ArcGISMapImageLayer in the map uses the "USA" map service as its data source. This service is hosted by ArcGIS Online, and is composed of four sublayers: "states", "counties", "cities", and "highways". Since the cities, counties, and states tables all have a POP2000 field, they can all execute a query against that attribute and a map extent.

Additional information

An ArcGISMapImageSublayer must be loaded before accessing its metadata or table. Use ArcGISMapImageLayer::loadTablesAndLayers to recursively load all sublayers and tables associated with a map image layer. Some sublayers do not have an associated table (group layers, for example) and some may not support specific types of queries. Consult the map service metadata for details.

Tags

Query, Sublayer, MapServer, Table

Sample Code

QueryMapImageSublayer.cppQueryMapImageSublayer.cppQueryMapImageSublayer.hQueryMapImageSublayer.qml
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// [WriteFile Name=QueryMapImageSublayer, Category=Layers]
// [Legal]
// Copyright 2018 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 "QueryMapImageSublayer.h"

#include "Basemap.h"
#include "Map.h"
#include "MapQuickView.h"
#include "ArcGISMapImageLayer.h"
#include "ArcGISMapImageSublayer.h"
#include "SimpleFillSymbol.h"
#include "SimpleLineSymbol.h"
#include "SimpleMarkerSymbol.h"
#include "QueryParameters.h"
#include "Graphic.h"
#include "GraphicsOverlay.h"
#include "GraphicListModel.h"

using namespace Esri::ArcGISRuntime;

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

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

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

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

  // Create a map using the streets vector basemap
  m_map = new Map(BasemapStyle::ArcGISStreets, this);

  // add map image layer
  m_usaImageLayer = new ArcGISMapImageLayer(QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer"), this);
  m_map->operationalLayers()->append(m_usaImageLayer);

  // add a graphics overlay
  m_selectionOverlay = new GraphicsOverlay(this);
  m_mapView->graphicsOverlays()->append(m_selectionOverlay);

  // create symbols
  createSymbols();

  // connect signals
  connectSignals();

  // set initial viewpoint
  Viewpoint vp(Point(-12716000, 4170400, SpatialReference::webMercator()), 6000000 /*scale*/);
  m_map->setInitialViewpoint(vp);

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

void QueryMapImageSublayer::connectSignals()
{
  connect(m_usaImageLayer, &ArcGISMapImageLayer::loadTablesAndLayersCompleted, this, [this](QUuid)
  {
    ArcGISSublayerListModel* sublayers = m_usaImageLayer->mapImageSublayers();
    if (sublayers->size() < 4)
      return;

    // get the sublayer's tables
    m_citiesTable = dynamic_cast<ArcGISMapImageSublayer*>(sublayers->at(0))->table();
    m_statesTable = dynamic_cast<ArcGISMapImageSublayer*>(sublayers->at(2))->table();
    m_countiesTable = dynamic_cast<ArcGISMapImageSublayer*>(sublayers->at(3))->table();

    // connect to city sublayer query signal
    connect(m_citiesTable, &ServiceFeatureTable::queryFeaturesCompleted, this, [this](QUuid, FeatureQueryResult* result)
    {
      addResultsAsGraphics(result, m_citySymbol);
      delete result;
    });

    // connect to county sublayer query signal
    connect(m_countiesTable, &ServiceFeatureTable::queryFeaturesCompleted, this, [this](QUuid, FeatureQueryResult* result)
    {
      addResultsAsGraphics(result, m_countySymbol);
      delete result;
    });

    // connect to states sublayer query signal
    connect(m_statesTable, &ServiceFeatureTable::queryFeaturesCompleted, this, [this](QUuid, FeatureQueryResult* result)
    {
      addResultsAsGraphics(result, m_stateSymbol);
      delete result;
    });
  });

  connect(m_usaImageLayer, &ArcGISMapImageLayer::doneLoading, this, [this](Error e)
  {
    if (!e.isEmpty())
      return;

    // load the sublayers and tables of the map image layer
    m_usaImageLayer->loadTablesAndLayers();
  });
}

void QueryMapImageSublayer::createSymbols()
{
  // create symbol for city selection
  m_citySymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle::Circle, QColor("red"), 16.0f /*size*/, this);

  // create symbol for county selection
  SimpleLineSymbol* countyOutline = new SimpleLineSymbol(SimpleLineSymbolStyle::Dash, QColor("cyan"), 2.0f /*width*/, this);
  m_countySymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::DiagonalCross, QColor("cyan"), countyOutline, this);

  // create symbol for state selection
  SimpleLineSymbol* stateOutline = new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("darkcyan"), 6.0f /*width*/, this);
  m_stateSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Null, QColor("transparent"), stateOutline, this);
}

void QueryMapImageSublayer::addResultsAsGraphics(FeatureQueryResult* result, Symbol* symbol)
{
  // get the iterator of features
  FeatureIterator iter = result->iterator();

  // Create local parent
  QObject localParent;

  // add a graphic for each feature
  while (iter.hasNext())
  {
    Feature* feat = iter.next(&localParent);
    Graphic* graphic = new Graphic(feat->geometry(), symbol, this);
    m_selectionOverlay->graphics()->append(graphic);
  }
}

void QueryMapImageSublayer::query(const QString& whereClause)
{
  if (!m_citiesTable || !m_countiesTable || !m_statesTable || !m_mapView || !m_selectionOverlay)
    return;

  // clear & delete previous graphics
  GraphicListModel* graphics = m_selectionOverlay->graphics();
  const int graphicSize = graphics->size();
  for (int i = 0; i < graphicSize; i++)
  {
    delete graphics->at(i);
  }
  graphics->clear();

  // create the parameters
  QueryParameters queryParams;
  queryParams.setGeometry(m_mapView->currentViewpoint(ViewpointType::BoundingGeometry).targetGeometry().extent());
  queryParams.setWhereClause(whereClause);

  // query the feature tables
  m_citiesTable->queryFeatures(queryParams);
  m_countiesTable->queryFeatures(queryParams);
  m_statesTable->queryFeatures(queryParams);
}

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