Feature layer selection

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Sample viewer app

Select features in a feature layer.

screenshot

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 sample

Click on a feature in the map. All features within a given tolerance (in pixels) of the click will be selected.

How it works

  1. Create a ServiceFeatureTable from a feature service URL.
  2. Create a FeatureLayer from the service feature table.
  3. Identify nearby features at the clicked location using identifyLayerWithMaxResults(featureLayer, mouse.x, mouse.y, tolerance, returnPopupsOnly, maxResults) on the map view.
  4. Select all identified features in the feature layer with selectFeatures(features).

Relevant API

  • Feature
  • FeatureLayer
  • ServiceFeatureTable

About the data

This sample uses the Gross Domestic Product, 1960-2016 feature service. Only the 2016 GDP values are shown.

Tags

features, layers, select, selection, tolerance

Sample Code

FeatureLayer_Selection.qml
                                                                                                                                    
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// [WriteFile Name=FeatureLayer_Selection, Category=Features]
// [Legal]
// Copyright 2016 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 QtQuick 2.6
import QtQuick.Controls 2.2
import Esri.ArcGISRuntime 100.12

Rectangle {
    width: 800
    height: 600


    property string displayText: "Click or tap to select features."


    // Map view UI presentation at top
    MapView {
        id: mapView
        anchors {
            left: parent.left
            right: parent.right
            top: parent.top
            bottom: messageBar.top
        }
        wrapAroundMode: Enums.WrapAroundModeDisabled

        Map {
            id: map
            Basemap {
                initStyle: Enums.BasemapStyleArcGISLightGray
            }

            FeatureLayer {
                id: featureLayer

                // feature table
                ServiceFeatureTable {
                    id: featureTable
                    url: "https://services1.arcgis.com/4yjifSiIG17X0gW4/arcgis/rest/services/GDP_per_capita_1960_2016/FeatureServer/0"
                }
            }

            onLoadStatusChanged: {
                if (loadStatus === Enums.LoadStatusLoaded) {
                    mapView.setViewpoint(viewPoint);
                }
            }
        }

        // initial viewpoint
        ViewpointExtent {
            id: viewPoint
            Envelope {
                xMin: -6603299.491810
                yMin: 1679677.742046
                xMax: 9002253.947487
                yMax: 8691318.054732
                SpatialReference {
                    wkid: 3857
                }
            }
        }

        //! [identify feature layer qml api snippet]
        onMouseClicked: {
            const tolerance = 22;
            const returnPopupsOnly = false;
            const maximumResults = 1000;
            mapView.identifyLayerWithMaxResults(featureLayer, mouse.x, mouse.y, tolerance, returnPopupsOnly, maximumResults);
        }

        onIdentifyLayerStatusChanged: {
            if (identifyLayerStatus === Enums.TaskStatusCompleted) {
                // clear any previous selections
                featureLayer.clearSelection();

                // create an array to store the features
                const identifiedObjects = [];
                for (let i = 0; i < identifyLayerResult.geoElements.length; i++){
                    const elem = identifyLayerResult.geoElements[i];
                    identifiedObjects.push(elem);
                }
                // cache the number of identifyLayerResult
                const count = identifyLayerResult.geoElements.length;

                // select the features in the feature layer
                featureLayer.selectFeatures(identifiedObjects);
                displayText = "%1 %2 selected.".arg(count).arg(count > 1 ? "features" : "feature");
            }
        }
        //! [identify feature layer qml api snippet]
    }

    Rectangle {
        id: messageBar
        anchors {
            left: parent.left
            right: parent.right
            bottom: parent.bottom
        }
        height: 30
        color: "lightgrey"
        border {
            width: 0.5
            color: "black"
        }

        Text {
            id: msgText
            anchors {
                verticalCenter: parent.verticalCenter
                left: parent.left
                leftMargin: 10
            }
            text: displayText
            font.pixelSize: 14
        }
    }
}

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