Identify features in all layers in a map.

Use case
IdentifyLayers allows users to tap on a map, returning features at that location across multiple layers. Because some layer types have sublayers, the sample recursively counts results for sublayers within each layer.
How to use the sample
Tap to identify features. An alert will show all layers with features under the cursor, as well as a layer count.
How it works
- The tapped position is passed to
MapView::identifyLayers - For each
IdentifyLayerResultin the results, features are counted.- Note: there is one identify result per layer with matching features; if the feature count is 0, that means a sublayer contains the matching features.
Relevant API
- IdentifyLayerResult
- IdentifyLayerResult::layerContent::name
- IdentifyLayerResult::sublayerResults
- MapView::identifyLayers
Additional information
The GeoView supports two methods of identify: identifyLayer(), which identifies features within a specific layer and identifyLayers(), which identifies features for all layers in the current view.
Tags
identify, recursion, recursive, sublayers
Sample Code
// [WriteFile Name=IdentifyLayers, Category=Maps]// [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
// sample headers#include "IdentifyLayers.h"
// ArcGIS Maps SDK headers#include "ArcGISMapImageLayer.h"#include "ArcGISSublayer.h"#include "ArcGISSublayerListModel.h"#include "Basemap.h"#include "Error.h"#include "FeatureLayer.h"#include "IdentifyLayerResult.h"#include "LayerListModel.h"#include "Map.h"#include "MapQuickView.h"#include "MapTypes.h"#include "Point.h"#include "ServiceFeatureTable.h"#include "SpatialReference.h"#include "Viewpoint.h"
// Qt headers#include <QFuture>#include <QQueue>#include <QUuid>
using namespace Esri::ArcGISRuntime;
IdentifyLayers::IdentifyLayers(QQuickItem* parent /* = nullptr */): QQuickItem(parent){}
void IdentifyLayers::init(){ // Register the map view for QML qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView"); qmlRegisterType<IdentifyLayers>("Esri.Samples", 1, 0, "IdentifyLayersSample");}
void IdentifyLayers::componentComplete(){ QQuickItem::componentComplete();
// find QML MapView component m_mapView = findChild<MapQuickView*>("mapView");
// Create a map using the topographic basemap m_map = new Map(BasemapStyle::ArcGISTopographic, this);
// add a map image layer QUrl mapServiceUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/SampleWorldCities/MapServer"); ArcGISMapImageLayer* imageLayer = new ArcGISMapImageLayer(mapServiceUrl, this); m_map->operationalLayers()->append(imageLayer);
// hide 2 of the sublayers in the map image layer connect(imageLayer, &ArcGISMapImageLayer::doneLoading, this, [imageLayer](const Error& e) { if (!e.isEmpty()) { qDebug() << e.message() << e.additionalMessage(); return; }
imageLayer->mapImageSublayers()->at(1)->setVisible(false); imageLayer->mapImageSublayers()->at(2)->setVisible(false); });
// add a feature layer QUrl featureLayerUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer/0"); ServiceFeatureTable* featureTable = new ServiceFeatureTable(featureLayerUrl, this); FeatureLayer* featureLayer = new FeatureLayer(featureTable, this); m_map->operationalLayers()->append(featureLayer);
// set an initial viewpoint const double mapScale = 68015210; const double x = -10977012.785807; const double y = 4514257.550369; const Point pt(x, y, SpatialReference::webMercator()); Viewpoint initialViewpoint(pt, mapScale); m_map->setInitialViewpoint(initialViewpoint);
// Set map to map view m_mapView->setMap(m_map);
// connect signals connectSignals();}
void IdentifyLayers::connectSignals(){ // identify layers on mouse click connect(m_mapView, &MapQuickView::mouseClicked, this, [this](QMouseEvent& mouseEvent) { const double tolerance = 12.0; const bool returnPopups = false; const int maxResults = 10;
m_mapView->identifyLayersAsync(mouseEvent.position(), tolerance, returnPopups, maxResults).then(this, [this](const QList<IdentifyLayerResult*>& results) { // reset the message text m_message = QString();
for (IdentifyLayerResult* result : results) { // lambda for calculating result count auto geoElementsCountFromResult = [] (IdentifyLayerResult* result) -> int { // create temp list QList<IdentifyLayerResult*> tempResults{result};
// use Depth First Search approach to handle recursion int count = 0; int index = 0;
while (index < tempResults.length()) { //get the result object from the array IdentifyLayerResult* identifyResult = tempResults[index];
// update count with geoElements from the result count += identifyResult->geoElements().length();
// check if the result has any sublayer results // if yes then add those result objects in the tempResults // array after the current result if (identifyResult->sublayerResults().length() > 0) { tempResults.append(identifyResult->sublayerResults().at(index)); }
// update the count and repeat index += 1; } return count; };
const int count = geoElementsCountFromResult(result); QString layerName = result->layerContent()->name(); m_message += QString("%1 : %2").arg(layerName).arg(count); m_message += "\n"; } //remove last newline character if (!m_message.isEmpty()) m_message.chop(1);
emit messageChanged(); emit showMessage(); qDeleteAll(results); });
});}// [WriteFile Name=IdentifyLayers, Category=Maps]// [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]
#ifndef IDENTIFYLAYERS_H#define IDENTIFYLAYERS_H
// Qt headers#include <QQuickItem>
namespace Esri::ArcGISRuntime{class Map;class MapQuickView;}
class IdentifyLayers : public QQuickItem{ Q_OBJECT Q_PROPERTY(QString message MEMBER m_message NOTIFY messageChanged)
public: explicit IdentifyLayers(QQuickItem* parent = nullptr); ~IdentifyLayers() override = default;
void componentComplete() override; static void init();
signals: void messageChanged(); void showMessage();
private: void connectSignals();
private: Esri::ArcGISRuntime::Map* m_map = nullptr; Esri::ArcGISRuntime::MapQuickView* m_mapView = nullptr; QString m_message;};
#endif // IDENTIFYLAYERS_H// [WriteFile Name=IdentifyLayers, Category=Maps]// [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]
import QtQuickimport QtQuick.Controlsimport Esri.Samples
IdentifyLayersSample { id: rootRectangle clip: true width: 800 height: 600
// add a mapView component MapView { anchors.fill: parent objectName: "mapView"
Component.onCompleted: { // Set the focus on MapView to initially enable keyboard navigation forceActiveFocus(); } }
Dialog { id: msgDialog modal: true x: Math.round(parent.width - width) / 2 y: Math.round(parent.height - height) / 2 standardButtons: Dialog.Ok property alias text : textLabel.text Text { id: textLabel text: message } }
onShowMessage: { if (message.length > 0) msgDialog.open(); }}// [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]
// sample headers#include "IdentifyLayers.h"
// ArcGIS Maps SDK headers#include "ArcGISRuntimeEnvironment.h"
// Qt headers#include <QCommandLineParser>#include <QDir>#include <QGuiApplication>#include <QQmlEngine>#include <QQuickView>
// Platform specific headers#ifdef Q_OS_WIN#include <Windows.h>#endif
#define STRINGIZE(x) #x#define QUOTE(x) STRINGIZE(x)
int main(int argc, char *argv[]){ Esri::ArcGISRuntime::ArcGISRuntimeEnvironment::setUseLegacyAuthentication(false); QGuiApplication app(argc, argv); app.setApplicationName(QString("IdentifyLayers"));
// Use of ArcGIS location services, such as basemap styles, geocoding, and routing services, // requires an access token. For more information see // https://links.esri.com/arcgis-runtime-security-auth.
// The following methods grant an access token:
// 1. User authentication: Grants a temporary access token associated with a user's ArcGIS account. // To generate a token, a user logs in to the app with an ArcGIS account that is part of an // organization in ArcGIS Online or ArcGIS Enterprise.
// 2. API key authentication: Get a long-lived access token that gives your application access to // ArcGIS location services. Go to the tutorial at https://links.esri.com/create-an-api-key. // Copy the API Key access token.
const QString accessToken = QString("");
if (accessToken.isEmpty()) { qWarning() << "Use of ArcGIS location services, such as the basemap styles service, requires" << "you to authenticate with an ArcGIS account or set the API Key property."; } else { Esri::ArcGISRuntime::ArcGISRuntimeEnvironment::setApiKey(accessToken); }
// Initialize the sample IdentifyLayers::init();
// Initialize application view QQuickView view; view.setResizeMode(QQuickView::SizeRootObjectToView);
QString arcGISRuntimeImportPath = QUOTE(ARCGIS_RUNTIME_IMPORT_PATH);
#if defined(LINUX_PLATFORM_REPLACEMENT) // on some linux platforms the string 'linux' is replaced with 1 // fix the replacement paths which were created QString replaceString = QUOTE(LINUX_PLATFORM_REPLACEMENT); arcGISRuntimeImportPath = arcGISRuntimeImportPath.replace(replaceString, "linux", Qt::CaseSensitive);#endif
// Add the import Path view.engine()->addImportPath(QDir(QCoreApplication::applicationDirPath()).filePath("qml")); // Add the Runtime and Extras path view.engine()->addImportPath(arcGISRuntimeImportPath);
// Set the source view.setSource(QUrl("qrc:/Samples/Maps/IdentifyLayers/IdentifyLayers.qml"));
view.show();
return app.exec();}