Export tiles

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Sample viewer app

Download tiles to a local tile cache file stored on the device.

screenshot

Use case

Field workers with limited network connectivity can use exported tiles as a basemap for use offline.

How to use the sample

Pan and zoom into the desired area, making sure the area is within the red boundary. Click the 'Export tiles' button to start the process. On successful completion you will see a preview of the downloaded tile package.

How it works

  1. Create and load a Map with a basemap style that includes a raster base layer.
  2. Create an ExportTileCacheTask with a URL from a raster base layer of a basemap.
  3. Create default ExportTileCacheParameters for the task, specifying extent, minimum scale and maximum scale. Limiting the difference between the minimum and maximum scales will decrease the size of the resulting tile package and the time it takes to create.
  4. Use the parameters and a path to create an ExportTileCacheJob from the task.
  5. Start the job, and when it completes successfully, get the resulting TileCache.
  6. Use the tile cache to create an ArcGISTiledLayer, and display it in the map.

Relevant API

  • ArcGISTiledLayer
  • ExportTileCacheJob
  • ExportTileCacheParameters
  • ExportTileCacheTask
  • TileCache

Additional information

ArcGIS tiled layers do not support reprojection, query, select, identify, or editing. See the Layer types discussion in the developers guide to learn more about the characteristics of ArcGIS tiled layers.

Tags

cache, download, offline

Sample Code

ExportTiles.qml
                                                                                                                                                                                                                                                                                                               
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// [WriteFile Name=ExportTiles, Category=Layers]
// [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 QtGraphicalEffects 1.0
import Esri.ArcGISRuntime 100.12
import Esri.ArcGISExtras 1.1

Rectangle {
    width: 800
    height: 600

    readonly property url outputTileCache: System.temporaryFolder.url + "/TileCacheQml_%1.tpkx".arg(new Date().getTime().toString())
    property Envelope tileCacheExtent: null
    property string statusText: ""
    property ExportTileCacheParameters params
    property var exportTileCacheProgress: 0

    // Create MapView that contains a Map
    MapView {
        id: mapView
        anchors.fill: parent
        Map {
            id: map
            // Add an imagery basemap to the map and get the url of the raster baselayer once it has loaded
            Basemap {
                initStyle: Enums.BasemapStyleArcGISImagery

                onLoadStatusChanged: {
                    if (loadStatus !== Enums.LoadStatusLoaded)
                        return;

                    exportTask.url = baseLayers.get(0).url;
                }
            }

            initialViewpoint: ViewpointCenter {
                center: Point {
                    x: -117
                    y: 35
                    spatialReference: SpatialReference { wkid: 4326 }
                }
                targetScale: 1e7
            }
        }
    }

    // Create ExportTileCacheTask
    //! [ExportTiles ExportTileCacheTask]

    ExportTileCacheTask {
        id: exportTask
        property var exportJob

        onCreateDefaultExportTileCacheParametersStatusChanged: {
            if (createDefaultExportTileCacheParametersStatus === Enums.TaskStatusCompleted) {
                params = defaultExportTileCacheParameters;

                // export the cache with the parameters
                executeExportTileCacheTask(params);
            }
        }

        function generateDefaultParameters() {
            // generate the default parameters with the extent and map scales specified
            exportTask.createDefaultExportTileCacheParameters(tileCacheExtent, mapView.mapScale, mapView.mapScale/10);
        }

        function executeExportTileCacheTask(params) {
            // execute the asynchronous task and obtain the job
            exportJob = exportTask.exportTileCache(params, outputTileCache);

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

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

                exportJob.start();
            } else {
                exportWindow.visible = true;
                statusText = "Export failed";
                exportWindow.hideWindow(5000);
            }
        }

        function updateJobStatus() {
            switch(exportJob.jobStatus) {
            case Enums.JobStatusFailed:
                statusText = "Export failed";
                exportWindow.hideWindow(5000);
                break;
            case Enums.JobStatusNotStarted:
                statusText = "Job not started";
                break;
            case Enums.JobStatusPaused:
                statusText = "Job paused";
                break;
            case Enums.JobStatusStarted:
                statusText = "In progress...";
                break;
            case Enums.JobStatusSucceeded:
                statusText = "Adding TPKX...";
                exportWindow.hideWindow(1500);
                displayOutputTileCache(exportJob.result);
                break;
            default:
                break;
            }
        }

        function updateExportProgress() {
            exportTileCacheProgress = exportJob.progress;
        }

        function displayOutputTileCache(tileCache) {
            // create a new tiled layer from the output tile cache
            const tiledLayer = ArcGISRuntimeEnvironment.createObject("ArcGISTiledLayer", { tileCache: tileCache } );

            // create a new basemap with the tiled layer
            const basemap = ArcGISRuntimeEnvironment.createObject("Basemap");
            basemap.baseLayers.append(tiledLayer);

            // set the new basemap on the map
            map.basemap = basemap;

            // zoom to the new layer and hide window once loaded
            tiledLayer.loadStatusChanged.connect(()=> {
                 if (tiledLayer.loadStatus === Enums.LoadStatusLoaded) {
                     extentRectangle.visible = false;
                     downloadButton.visible = false;

                     const prevMapScale = mapView.mapScale;
                     mapView.setViewpointScale(prevMapScale * .5);
                     map.minScale = prevMapScale;
                     map.maxScale = prevMapScale / 10;
                 }
             });
        }

        Component.onDestruction: {
            if (exportJob) {
                exportJob.jobStatusChanged.disconnect(updateJobStatus);
                exportJob.progressChanged.disconnect(updateExportProgress);
            }
        }
    }
    //! [ExportTiles ExportTileCacheTask]

    Rectangle {
        id: extentRectangle
        anchors.centerIn: parent
        width: parent.width - (50)
        height: parent.height - (125)
        color: "transparent"
        border {
            color: "red"
            width: 3
        }
    }

    // Create the download button to export the tile cache
    Rectangle {
        id: downloadButton
        property bool pressed: false
        anchors {
            horizontalCenter: parent.horizontalCenter
            bottom: parent.bottom
            bottomMargin: 23
        }

        width: 130
        height: 35
        color: pressed ? "#959595" : "#D6D6D6"
        radius: 5
        border {
            color: "#585858"
            width: 1
        }

        Row {
            anchors.fill: parent
            spacing: 5
            Image {
                width: 38
                height: width
                source: "qrc:/Samples/Layers/ExportTiles/download.png"
            }
            Text {
                anchors.verticalCenter: parent.verticalCenter
                text: "Export tiles"
                font.pixelSize: 14
                color: "#474747"
            }
        }

        MouseArea {
            anchors.fill: parent
            onPressed: downloadButton.pressed = true
            onReleased: downloadButton.pressed = false
            onClicked: {
                getRectangleEnvelope();
            }

            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);
                tileCacheExtent = GeometryEngine.project(envBuilder.geometry, Factory.SpatialReference.createWebMercator());
                exportTask.generateDefaultParameters();
            }
        }
    }

    // Create a window to display the export window
    Rectangle {
        id: exportWindow
        anchors.fill: parent
        color: "transparent"
        visible: false
        clip: true

        RadialGradient {
            anchors.fill: parent
            opacity: 0.7
            gradient: Gradient {
                GradientStop { position: 0.0; color: "lightgrey" }
                GradientStop { position: 0.7; color: "black" }
            }
        }

        MouseArea {
            anchors.fill: parent
            onClicked: mouse.accepted = true
            onWheel: wheel.accepted = true
        }

        Rectangle {
            anchors.centerIn: parent
            width: 140
            height: 145
            color: "lightgrey"
            opacity: 0.8
            radius: 5
            border {
                color: "#4D4D4D"
                width: 1
            }

            Column {
                anchors {
                    fill: parent
                    margins: 10
                }
                spacing: 10

                BusyIndicator {
                    anchors.horizontalCenter: parent.horizontalCenter
                }

                Text {
                    anchors.horizontalCenter: parent.horizontalCenter
                    text: statusText
                    font.pixelSize: 16
                }

                Text {
                    anchors.horizontalCenter: parent.horizontalCenter
                    text: exportTileCacheProgress + "% Completed"
                    font.pixelSize: 16
                }
            }
        }

        Timer {
            id: hideWindowTimer
            onTriggered: exportWindow.visible = false;
        }

        function hideWindow(time) {
            hideWindowTimer.interval = time;
            hideWindowTimer.restart();
        }
    }
}

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