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...ed/Samples/Download raster tiles to local cache/DownloadRasterTilesToLocalCacheView.swift
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| // Copyright 2026 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 | ||
| // | ||
| // https://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. | ||
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| import ArcGIS | ||
| import SwiftUI | ||
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| struct DownloadRasterTilesToLocalCacheView: View { | ||
| /// The view model for the sample. | ||
| @State private var model = Model() | ||
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| /// The current scale of the map view, used as the export's minimum scale. | ||
| @State private var mapViewScale = 0.0 | ||
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| /// A Boolean value indicating whether the exported tiles preview is showing. | ||
| @State private var isShowingPreview = false | ||
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| /// The error shown in the error alert. | ||
| @State private var error: Error? | ||
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| /// The insets that define the export extent within the map view. | ||
| private let extentInsets = EdgeInsets(top: 20, leading: 20, bottom: 44, trailing: 20) | ||
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| var body: some View { | ||
| MapViewReader { mapViewProxy in | ||
| GeometryReader { geometryProxy in | ||
| MapView(map: model.map) | ||
| .onScaleChanged { mapViewScale = $0 } | ||
| .overlay { | ||
| // Draws a red rectangle to emphasize the extent that | ||
| // will be exported. | ||
| Rectangle() | ||
| .stroke(.red, lineWidth: 2) | ||
| .padding(extentInsets) | ||
| } | ||
| .overlay(alignment: .center) { | ||
|
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| if let job = model.exportTileCacheJob { | ||
| exportProgressView(job: job) | ||
| } | ||
| } | ||
| .toolbar { | ||
| ToolbarItem(placement: .bottomBar) { | ||
| Button("Export Tiles") { | ||
| Task { | ||
| await exportTiles( | ||
| mapViewProxy: mapViewProxy, | ||
| size: geometryProxy.size | ||
| ) | ||
| } | ||
| } | ||
| .disabled(model.exportTileCacheJob != nil) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| .sheet(isPresented: $isShowingPreview, onDismiss: model.removePreview) { | ||
| previewSheet | ||
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| } | ||
| .errorAlert(presentingError: $error) | ||
| } | ||
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| /// A progress indicator and cancel button shown while tiles are exporting. | ||
| private func exportProgressView(job: ExportTileCacheJob) -> some View { | ||
| VStack(spacing: 16) { | ||
| Text("Exporting tiles…") | ||
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| // Observes the job's progress to update the bar automatically. | ||
| ProgressView(job.progress) | ||
| .progressViewStyle(.linear) | ||
| Button("Cancel", role: .destructive) { | ||
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| Task { await model.cancelExport() } | ||
| } | ||
| } | ||
| .padding() | ||
| .frame(maxWidth: 220) | ||
| .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 12)) | ||
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| } | ||
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| /// A sheet that previews the exported tile cache in its own map. | ||
| @ViewBuilder private var previewSheet: some View { | ||
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| NavigationStack { | ||
| if let previewMap = model.previewMap { | ||
| MapView(map: previewMap) | ||
| .navigationTitle("Exported Tiles") | ||
| .navigationBarTitleDisplayMode(.inline) | ||
| .toolbar { | ||
| ToolbarItem(placement: .confirmationAction) { | ||
| Button("Done") { isShowingPreview = false } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| /// Exports the tiles within the red rectangle and shows the preview sheet. | ||
| /// - Parameters: | ||
| /// - mapViewProxy: The proxy used to convert screen points to locations. | ||
| /// - size: The size of the map view, used to locate the export extent. | ||
| private func exportTiles(mapViewProxy: MapViewProxy, size: CGSize) async { | ||
| // Converts the red rectangle's corners to a geographic envelope. | ||
| let rect = CGRect( | ||
| x: extentInsets.leading, | ||
| y: extentInsets.top, | ||
| width: size.width - extentInsets.leading - extentInsets.trailing, | ||
| height: size.height - extentInsets.top - extentInsets.bottom | ||
| ) | ||
| guard | ||
| let min = mapViewProxy.location(fromScreenPoint: CGPoint(x: rect.minX, y: rect.maxY)), | ||
| let max = mapViewProxy.location(fromScreenPoint: CGPoint(x: rect.maxX, y: rect.minY)) | ||
| else { return } | ||
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| do { | ||
| try await model.exportTiles( | ||
| extent: Envelope(min: min, max: max), | ||
| currentScale: mapViewScale | ||
| ) | ||
| isShowingPreview = true | ||
| } catch { | ||
| self.error = error | ||
| } | ||
| } | ||
| } | ||
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| extension DownloadRasterTilesToLocalCacheView { | ||
| /// The model that stores the maps and runs the export task for this sample. | ||
| @MainActor | ||
| @Observable | ||
| final class Model { | ||
| /// A map of the world street map tiled layer. | ||
| let map: Map | ||
|
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| /// A map that previews the exported tile cache, if one exists. | ||
| private(set) var previewMap: Map? | ||
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| /// The export job currently downloading the tile package, if any. | ||
| private(set) var exportTileCacheJob: ExportTileCacheJob? | ||
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| /// The tiled layer that provides both the basemap and the export source. | ||
| private let tiledLayer = ArcGISTiledLayer(url: .worldOceanBase) | ||
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| /// The task that exports tiles from the tiled layer's service. | ||
| private let exportTask = ExportTileCacheTask(url: .worldOceanBase) | ||
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| /// A URL to the temporary directory storing the exported tile package. | ||
| private let temporaryDirectory = FileManager.createTemporaryDirectory() | ||
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| init() { | ||
| // Creates a map with a basemap made from the tiled layer, and limits | ||
| // its minimum scale to avoid requesting a huge download. | ||
| map = Map(basemap: Basemap(baseLayer: tiledLayer)) | ||
| map.minScale = 1e7 | ||
| map.initialViewpoint = Viewpoint( | ||
| center: Point(x: -117, y: 34, spatialReference: .wgs84), | ||
| scale: 1e7 | ||
| ) | ||
| } | ||
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| deinit { | ||
| // Removes the temporary directory and all of its content. | ||
| try? FileManager.default.removeItem(at: temporaryDirectory) | ||
| } | ||
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| /// Exports the tiles within an extent to a local tile package and builds | ||
| /// a preview map from the result. | ||
| /// - Parameters: | ||
| /// - extent: The geographic area of interest to export. | ||
| /// - currentScale: The map's current scale, used as the minimum scale. | ||
| func exportTiles(extent: Envelope, currentScale: Double) async throws { | ||
| // Loads the task to access its service metadata. | ||
| try await exportTask.load() | ||
| guard | ||
| let mapServiceInfo = exportTask.mapServiceInfo, | ||
| mapServiceInfo.allowsExportTiles | ||
| else { | ||
| throw ExportError.notSupported | ||
| } | ||
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| // Uses the current scale as the min scale and the tiled layer's max | ||
| // scale as the max scale. | ||
| let maxScale = tiledLayer.maxScale ?? 0 | ||
| let minScale = Swift.max(currentScale, maxScale) | ||
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| // Builds the default parameters for the extent and scale range. | ||
| let parameters = try await exportTask.makeDefaultExportTileCacheParameters( | ||
| areaOfInterest: extent, | ||
| minScale: minScale, | ||
| maxScale: maxScale | ||
| ) | ||
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| // Uses the compact V2 format (.tpkx) when supported, otherwise the | ||
| // legacy compact format (.tpk). | ||
| let fileExtension = mapServiceInfo.allowsExportTileCacheCompactV2 ? "tpkx" : "tpk" | ||
| let downloadURL = temporaryDirectory | ||
| .appendingPathComponent("myTileCache", isDirectory: false) | ||
| .appendingPathExtension(fileExtension) | ||
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| // Creates and starts the export job. | ||
| let job = exportTask.makeExportTileCacheJob( | ||
| parameters: parameters, | ||
| downloadFileURL: downloadURL | ||
| ) | ||
| exportTileCacheJob = job | ||
| job.start() | ||
| defer { exportTileCacheJob = nil } | ||
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| // Awaits the resulting tile cache and builds a preview map from it. | ||
| let tileCache = try await job.output | ||
| let previewLayer = ArcGISTiledLayer(tileCache: tileCache) | ||
| let previewMap = Map(basemap: Basemap(baseLayer: previewLayer)) | ||
| previewMap.initialViewpoint = Viewpoint(boundingGeometry: extent) | ||
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| self.previewMap = previewMap | ||
| } | ||
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| /// Cancels the running export job, if one exists. | ||
| func cancelExport() async { | ||
| await exportTileCacheJob?.cancel() | ||
| exportTileCacheJob = nil | ||
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| } | ||
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| /// Releases the preview map and removes the exported tile package. | ||
| func removePreview() { | ||
| previewMap = nil | ||
| try? FileManager.default.removeItem(at: temporaryDirectory) | ||
| } | ||
| } | ||
| } | ||
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| private extension DownloadRasterTilesToLocalCacheView.Model { | ||
| /// An error indicating the service does not support exporting tiles. | ||
| enum ExportError: LocalizedError { | ||
| case notSupported | ||
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| var errorDescription: String? { | ||
| switch self { | ||
| case .notSupported: | ||
| return "Exporting tiles is not supported for the service." | ||
| } | ||
| } | ||
| } | ||
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| } | ||
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| private extension FileManager { | ||
| /// Creates a uniquely named temporary directory and returns its URL. | ||
| static func createTemporaryDirectory() -> URL { | ||
| let url = FileManager.default.temporaryDirectory | ||
| .appendingPathComponent(ProcessInfo().globallyUniqueString) | ||
| try? FileManager.default.createDirectory(at: url, withIntermediateDirectories: true) | ||
| return url | ||
| } | ||
| } | ||
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| private extension URL { | ||
| /// The URL of the World Ocean Base (for Export) tile service. | ||
| static var worldOceanBase: URL { | ||
| URL(string: "https://tiledbasemaps.arcgis.com/arcgis/rest/services/Ocean/World_Ocean_Base/MapServer")! | ||
| } | ||
| } | ||
42 changes: 42 additions & 0 deletions
42
Shared/Samples/Download raster tiles to local cache/README.md
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| # Download raster tiles to local cache | ||
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| Download tiles to a local tile cache file stored on the device. | ||
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|  | ||
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| ## Use case | ||
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| Field workers with limited network connectivity can use exported tiles as a basemap for use offline. | ||
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| ## How to use the sample | ||
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| 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. | ||
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| ## How it works | ||
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| 1. Create a map and set its `minScale` to 10,000,000. Limiting the scale in this sample limits the potential size of the selection area, thereby keeping the exported tile package to a reasonable size. | ||
| 2. Create an `ExportTileCacheTask`, passing in the URI of the tiled layer. | ||
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| 3. Create default `ExportTileCacheParameters` for the task, specifying extent, minimum scale and maximum scale. | ||
| 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. | ||
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| ## Relevant API | ||
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| * ArcGISTiledLayer | ||
| * ExportTileCacheJob | ||
| * ExportTileCacheParameters | ||
| * ExportTileCacheTask | ||
| * TileCache | ||
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| ## About the data | ||
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| The sample uses a [World Ocean Base (for Export)](https://www.arcgis.com/home/item.html?id=5d85d897aee241f884158aa514954443) map service that features marine bathymetry. The service supports "estimate export tiles size" and "export tiles" operations. | ||
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| ## Additional information | ||
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| ArcGIS tiled layers do not support reprojection, query, select, identify, or editing. See the [Layer types](https://developers.arcgis.com/net/layers/#layer-types) discussion in the developers guide to learn more about the characteristics of ArcGIS tiled layers. The map service behind a tiled layer may support [Export Tiles](https://developers.arcgis.com/rest/services-reference/enterprise/export-tiles-map-service/) operation. You can also specify the maximum tiles clients will be allowed to download for the service. | ||
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| ## Tags | ||
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| cache, download, offline | ||
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