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Select features in a feature layer.
Use case
Selecting features, whether by query or identify, can be an important step both in editing data and visualizing results. One possible use case would be to query a feature layer containing street furniture. A query might look for type "bench" and return a list of bench features contained in the features with an attribute of type bench. These might be selected for further editing (see FeatureQueryResult) or may just be highlighted visually.
How to use the sampleClick on a feature in the map. All features within a given tolerance (in pixels) of the click will be selected.
How it worksServiceFeatureTable from a feature service URL.FeatureLayer from the service feature table.identifyLayerAsync(featureLayer, mouseEvent.position(), tolerance, returnPopupsOnly, maxResults) on the map view.selectFeatures(features).This sample uses the Gross Domestic Product, 1960-2016 feature service. Only the 2016 GDP values are shown.
features, layers, select, selection, tolerance
Sample CodeFeatureLayerSelection.cpp FeatureLayerSelection.cpp FeatureLayerSelection.h FeatureLayerSelection.qml
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// [WriteFile Name=FeatureLayerSelection, Category=Features]
// [Legal]
// Copyright 2022 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
// sample headers
#include "FeatureLayerSelection.h"
// ArcGIS Maps SDK headers
#include "Envelope.h"
#include "Feature.h"
#include "FeatureLayer.h"
#include "IdentifyLayerResult.h"
#include "LayerListModel.h"
#include "Map.h"
#include "MapQuickView.h"
#include "MapTypes.h"
#include "ServiceFeatureTable.h"
#include "SpatialReference.h"
#include "Viewpoint.h"
// Qt headers
#include <QFuture>
#include <QUuid>
// STL headers
#include <memory>
using namespace Esri::ArcGISRuntime;
FeatureLayerSelection::FeatureLayerSelection(QObject* parent /* = nullptr */):
QObject(parent),
m_map(new Map(BasemapStyle::ArcGISLightGray, this))
{
m_map->setInitialViewpoint(Viewpoint(Envelope(-6603299.491810, 1679677.742046, 9002253.947487, 8691318.054732, SpatialReference::webMercator())));
m_featureTable = new ServiceFeatureTable(QUrl("https://services1.arcgis.com/4yjifSiIG17X0gW4/arcgis/rest/services/GDP_per_capita_1960_2016/FeatureServer/0"), this);
m_featureLayer = new FeatureLayer(m_featureTable, this);
m_map->operationalLayers()->append(m_featureLayer);
}
FeatureLayerSelection::~FeatureLayerSelection() = default;
void FeatureLayerSelection::init()
{
// Register the map view for QML
qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
qmlRegisterType<FeatureLayerSelection>("Esri.Samples", 1, 0, "FeatureLayerSelectionSample");
}
MapQuickView* FeatureLayerSelection::mapView() const
{
return m_mapView;
}
QString FeatureLayerSelection::selectedFeatureText() const
{
return m_selectedFeatureText;
}
// Set the view (created in QML)
void FeatureLayerSelection::setMapView(MapQuickView* mapView)
{
if (!mapView || mapView == m_mapView)
return;
m_mapView = mapView;
m_mapView->setMap(m_map);
connectSignals();
emit mapViewChanged();
}
//! [identify feature layer qml api snippet]
void FeatureLayerSelection::connectSignals()
{
// lambda expression for the mouse press event on the mapview... do an identify operation
connect(m_mapView, &MapQuickView::mouseClicked, this, [this](QMouseEvent& mouseEvent)
{
constexpr double tolerance = 22.0;
constexpr bool returnPopupsOnly = false;
constexpr int maximumResults = 1000;
m_mapView->identifyLayerAsync(m_featureLayer, mouseEvent.position(), tolerance, returnPopupsOnly, maximumResults).then(this,
[this](IdentifyLayerResult* result)
{
onIdentifyLayerCompleted_(result);
});
});
}
void FeatureLayerSelection::onIdentifyLayerCompleted_(IdentifyLayerResult* result)
{
auto identifyResult = std::unique_ptr<IdentifyLayerResult>(result);
if (!identifyResult)
return;
// clear any existing selection
m_featureLayer->clearSelection();
// create a list to store the identified elements
QList<Feature*> identifiedFeatures;
for (int i = 0; i < identifyResult->geoElements().size(); i++)
{
GeoElement* element = identifyResult->geoElements().at(i);
if (nullptr != element)
{
// add the element to the list and take ownership of it.
Feature* feature = static_cast<Feature*>(element);
feature->setParent(this);
identifiedFeatures.append(feature);
}
}
// select the identified features
m_featureLayer->selectFeatures(identifiedFeatures);
// update the member with the number of selected features
const qsizetype count = identifiedFeatures.length();
m_selectedFeatureText = count > 1 ? QString::number(count) + " features selected." : QString::number(count) + " feature selected.";
emit selectedFeatureTextChanged();
}
//! [identify feature layer qml api snippet]RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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