Generate offline map

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Take a web map offline.

screenshot

Use case

Taking a web map offline allows users continued productivity when their network connectivity is poor or nonexistent. For example, by taking a map offline, a field worker inspecting utility lines in remote areas could still access a feature's location and attribute information.

How to use the sample

When the map loads, zoom to the extent you want to take offline. The red border shows the extent that will be downloaded. Tap the "Generate offline map" button to start the offline map job. The progress view will show the job's progress. When complete, the offline map will replace the online map in the map view.

How it works

  1. Create a Map with a PortalItem pointing to the web map.
  2. Create GenerateOfflineMapParameters specifying the download area geometry, minimum scale, and maximum scale.
  3. Create an OfflineMapTask with the map.
  4. Create the OfflineMapJob with OfflineMapTask.generateOfflineMap(params, downloadDirectoryPath) and start it with OfflineMapJob.start().
  5. When the job is done, get the offline map with OfflineMapJob.result.offlineMap.

Relevant API

  • GenerateOfflineMapJob
  • GenerateOfflineMapParameters
  • GenerateOfflineMapResult
  • OfflineMapTask
  • Portal

About the data

The map used in this sample shows the stormwater network within Naperville, IL, USA, with cartography designed for web and mobile devices with offline support.

Additional information

The creation of the offline map can be fine-tuned using parameter overrides for feature layers, or by using local basemaps. For examples on these, please consult the samples, "Generate Offline Map (Overrides)" and "Generate offline map with local basemap".

Tags

download, offline, save, web map

Sample Code

GenerateOfflineMap.qmlDownloadButton.qmlGenerateWindow.qml
                                                                                                                                                                                                                 
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// [WriteFile Name=GenerateOfflineMap, 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 QtQuick 2.6
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3
import Esri.ArcGISRuntime 100.12
import Esri.ArcGISExtras 1.1

Rectangle {
    id: rootRectangle
    clip: true
    width: 800
    height: 600

    readonly property url outputMapPackage: System.temporaryFolder.url + "/OfflineMap_%1.mmpk".arg(new Date().getTime().toString())
    readonly property string webMapId: "acc027394bc84c2fb04d1ed317aac674"

    MapView {
        id: mapView
        anchors.fill: parent

        // Create a Map from a Portal Item
        Map {
            id: map

            PortalItem {
                id: mapPortalItem

                itemId: webMapId
                Portal {
                    loginRequired: false
                }
            }
        }

        // Create a button and anchor it to the attribution top
        DownloadButton {
            id: downloadButton
            anchors {
                horizontalCenter: parent.horizontalCenter
                bottom: mapView.attributionTop
                margins: 5
            }
            visible: map.loadStatus === Enums.LoadStatusLoaded

            onButtonClicked: extentRectangle.getRectangleEnvelope();
        }
    }

    // Create an extent rectangle for selecting the offline area
    Rectangle {
        id: extentRectangle
        anchors.centerIn: parent
        width: parent.width - 50
        height: parent.height - 125
        color: "transparent"
        visible: map.loadStatus === Enums.LoadStatusLoaded
        border {
            color: "red"
            width: 3
        }

        function getRectangleEnvelope() {
            const corner1 = mapView.screenToLocation(extentRectangle.x, extentRectangle.y);
            const corner2 = mapView.screenToLocation((extentRectangle.x + extentRectangle.width), (extentRectangle.y + extentRectangle.height));
            const envBuilder = ArcGISRuntimeEnvironment.createObject("EnvelopeBuilder");
            envBuilder.setCorners(corner1, corner2);
            const mapExtent = GeometryEngine.project(envBuilder.geometry, Factory.SpatialReference.createWebMercator());
            offlineMapTask.createDefaultGenerateOfflineMapParameters(mapExtent);
        }
    }


    // Create Offline Map Task
    OfflineMapTask {
        id: offlineMapTask
        portalItem: mapPortalItem
        property var generateJob

        onErrorChanged: console.log("error:", error.message, error.additionalMessage);

        onCreateDefaultGenerateOfflineMapParametersStatusChanged: {
            if (createDefaultGenerateOfflineMapParametersStatus !== Enums.TaskStatusCompleted)
                return;

            // Take the map offline once the parameters are generated
            takeMapOffline(offlineMapTask.createDefaultGenerateOfflineMapParametersResult);
        }


        function takeMapOffline(parameters) {
            // create the job
            generateJob = offlineMapTask.generateOfflineMap(parameters, outputMapPackage);

            // check if job is valid
            if (generateJob) {
                // show the export window
                generateWindow.visible = true;

                // connect to the job's status changed signal to know once it is done
                generateJob.jobStatusChanged.connect(updateJobStatus);
                // connect to the job's progress changed signal
                generateJob.progressChanged.connect(updateProgress);

                generateJob.start();
            } else {
                generateWindow.visible = true;
                generateWindow.statusText = "Task failed";
                generateWindow.hideWindow(5000);
            }
        }

        function updateJobStatus() {
            switch(generateJob.jobStatus) {
            case Enums.JobStatusFailed:
                generateWindow.statusText = "Task failed";
                generateWindow.hideWindow(5000);
                break;
            case Enums.JobStatusNotStarted:
                generateWindow.statusText = "Job not started";
                break;
            case Enums.JobStatusPaused:
                generateWindow.statusText = "Job paused";
                break;
            case Enums.JobStatusStarted:
                generateWindow.statusText = "In progress";
                break;
            case Enums.JobStatusSucceeded:
                // show any layer errors
                if (generateJob.result.hasErrors) {
                    const layerErrors = generateJob.result.layerErrors;
                    let errorText = "";
                    for (let i = 0; i < layerErrors.length; i++) {
                        const errorPair = layerErrors[i];
                        errorText += errorPair.layer.name + ": " + errorPair.error.message + "\n";
                    }
                    msgDialog.detailedText = errorText;
                    msgDialog.open();
                }

                // show the map
                generateWindow.statusText = "Complete";
                generateWindow.hideWindow(1500);
                displayOfflineMap(generateJob.result);
                break;
            default:
                console.log("default");
                break;
            }
        }

        function updateProgress() {
            generateWindow.progressText = generateJob.progress;
        }

        function displayOfflineMap(result) {
            // Set the offline map to the MapView
            mapView.map = result.offlineMap;
            downloadButton.visible = false;
            extentRectangle.visible = false;
        }

        Component.onDestruction: {
            if (generateJob) {
                generateJob.jobStatusChanged.disconnect(updateJobStatus);
                generateJob.progressChanged.disconnect(updateProgress);
            }
        }
    }

    GenerateWindow {
        id: generateWindow
        anchors.fill: parent
    }

    Dialog {
        id: msgDialog
        modal: true
        x: Math.round(parent.width - width) / 2
        y: Math.round(parent.height - height) / 2
        standardButtons: Dialog.Ok
        title: "Layer Errors"
        property alias text : textLabel.text
        property alias detailedText : detailsLabel.text
        ColumnLayout {
            Text {
                id: textLabel
                text: "Some layers could not be taken offline."
            }
            Text {
                id: detailsLabel
            }
        }
    }
}

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