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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 IdentifyLayerResult
in 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
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.
identify, recursion, recursive, sublayers
Sample CodeIdentifyLayers.cpp IdentifyLayers.cpp IdentifyLayers.h IdentifyLayers.qml
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// [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
# include "IdentifyLayers.h"
# include "Map.h"
# include "MapQuickView.h"
# include "Basemap.h"
# include "ArcGISMapImageLayer.h"
# include "FeatureLayer.h"
# include "ServiceFeatureTable.h"
# include "Viewpoint.h"
# include "Point.h"
# include "IdentifyLayerResult.h"
# include "Error.h"
# include "MapTypes.h"
# include "TaskWatcher.h"
# include "LayerListModel.h"
# include "ArcGISSublayerListModel.h"
# include "ArcGISSublayer.h"
# include "SpatialReference.h"
# 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-> identifyLayers (mouseEvent. position (). x (), mouseEvent. position (). y (), tolerance, returnPopups, maxResults);
});
// handle the identify results
connect (m_mapView, &MapQuickView::identifyLayersCompleted, this , [ this ]( const QUuid&, const QList<IdentifyLayerResult*>& results)
{
// reset the message text
m_message = QString ();
int i = 0 ;
for (IdentifyLayerResult* result : results)
{
++i;
// 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);
// add new line character if not the final element inthe array
if (i != results. length ())
m_message += "\n" ;
}
emit messageChanged ();
emit showMessage ();
qDeleteAll (results);
});
}