a8f4f70636
See https://github.com/pre-commit/pre-commit-hooks?tab=readme-ov-file#trailing-whitespace
151 lines
7.4 KiB
Markdown
151 lines
7.4 KiB
Markdown
# Download Offline Pack
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Download a region as an offline pack
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> Note: This example uses UIKit.
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This example shows how to download a region as an offline pack. This particular example kicks off the download as soon as the map finished loading. For more control when and how to manage offline regions, see <doc:ManageOfflineRegionsExample>.
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First, you need to define a ``MLNTilePyramidOfflineRegion``. Note that you should be conservative with your zoom level, because each individual tile in the tile pyramid will be individually downloaded. If you want to make a large area available offline, you should prepare a bundle, download this manually and use ``MLNOfflineStorage/addContentsOfURL:withCompletionHandler:``. However, this is outside of the scope of this example.
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You can pass along some user data / context with ``MLNOfflineStorage/addPackForRegion:withContext:completionHandler:``. This can be read in the notififications that are emitted. You should listen for these notifications using the names defined by
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- ``MLNOfflinePackProgressChangedNotification``
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- ``MLNOfflinePackErrorNotification``, and
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- ``MLNOfflinePackMaximumMapboxTilesReachedNotification``
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as is shown in the example. Note that this last notification is a historical artifact, your tile provider may not have a maximum number of tiles you are allowed to store.
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<!-- include-example(OfflinePackExample) -->
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```swift
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class OfflinePackExample: UIViewController, MLNMapViewDelegate {
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var mapView: MLNMapView!
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var progressView: UIProgressView!
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let jsonDecoder = JSONDecoder()
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struct UserData: Codable {
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var name: String
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}
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override func viewDidLoad() {
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super.viewDidLoad()
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mapView = MLNMapView(frame: view.bounds, styleURL: AMERICANA_STYLE)
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mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
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mapView.tintColor = .gray
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mapView.delegate = self
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view.addSubview(mapView)
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mapView.setCenter(CLLocationCoordinate2D(latitude: 22.27933, longitude: 114.16281),
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zoomLevel: 13, animated: false)
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// Setup offline pack notification handlers.
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NotificationCenter.default.addObserver(self, selector: #selector(offlinePackProgressDidChange), name: NSNotification.Name.MLNOfflinePackProgressChanged, object: nil)
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NotificationCenter.default.addObserver(self, selector: #selector(offlinePackDidReceiveError), name: NSNotification.Name.MLNOfflinePackError, object: nil)
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NotificationCenter.default.addObserver(self, selector: #selector(offlinePackDidReceiveMaximumAllowedMapboxTiles), name: NSNotification.Name.MLNOfflinePackMaximumMapboxTilesReached, object: nil)
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}
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func mapViewDidFinishLoadingMap(_: MLNMapView) {
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// Start downloading tiles and resources for z13-14.
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startOfflinePackDownload()
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}
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override func viewDidDisappear(_ animated: Bool) {
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super.viewDidDisappear(animated)
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// When leaving this view controller, suspend offline downloads.
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guard let packs = MLNOfflineStorage.shared.packs else { return }
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for pack in packs {
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if let userInfo = try? jsonDecoder.decode(UserData.self, from: pack.context) {
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print("Suspending download of offline pack: '\(userInfo.name)'")
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}
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pack.suspend()
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}
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}
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func startOfflinePackDownload() {
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// Create a region that includes the current viewport and any tiles needed to view it when zoomed further in.
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// Because tile count grows exponentially with the maximum zoom level, you should be conservative with your `toZoomLevel` setting.
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let region = MLNTilePyramidOfflineRegion(styleURL: mapView.styleURL, bounds: mapView.visibleCoordinateBounds, fromZoomLevel: mapView.zoomLevel, toZoomLevel: 14)
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// Store some data for identification purposes alongside the downloaded resources.
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let jsonEncoder = JSONEncoder()
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let userInfo = UserData(name: "My Offline Pack")
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let encodedUserInfo = try! jsonEncoder.encode(userInfo)
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print(encodedUserInfo)
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// Create and register an offline pack with the shared offline storage object.
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MLNOfflineStorage.shared.addPack(for: region, withContext: encodedUserInfo) { pack, error in
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guard error == nil else {
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// The pack couldn’t be created for some reason.
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print("Error: \(error?.localizedDescription ?? "unknown error")")
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return
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}
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// Start downloading.
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pack!.resume()
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}
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}
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// MARK: - MLNOfflinePack notification handlers
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@objc func offlinePackProgressDidChange(notification: NSNotification) {
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// Get the offline pack this notification is regarding,
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// and the associated user info for the pack; in this case, `name = My Offline Pack`
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if let pack = notification.object as? MLNOfflinePack,
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let userInfo = try? jsonDecoder.decode(UserData.self, from: pack.context)
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{
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let progress = pack.progress
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// or notification.userInfo![MLNOfflinePackProgressUserInfoKey]!.MLNOfflinePackProgressValue
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let completedResources = progress.countOfResourcesCompleted
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let expectedResources = progress.countOfResourcesExpected
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// Calculate current progress percentage.
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let progressPercentage = Float(completedResources) / Float(expectedResources)
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// Setup the progress bar.
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if progressView == nil {
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progressView = UIProgressView(progressViewStyle: .default)
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let frame = view.bounds.size
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progressView.frame = CGRect(x: frame.width / 4, y: frame.height * 0.75, width: frame.width / 2, height: 10)
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view.addSubview(progressView)
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}
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progressView.progress = progressPercentage
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// If this pack has finished, print its size and resource count.
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if completedResources == expectedResources {
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let byteCount = ByteCountFormatter.string(fromByteCount: Int64(pack.progress.countOfBytesCompleted), countStyle: ByteCountFormatter.CountStyle.memory)
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print("Offline pack “\(userInfo.name)” completed: \(byteCount), \(completedResources) resources")
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} else {
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// Otherwise, print download/verification progress.
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print("Offline pack “\(userInfo.name)” has \(completedResources) of \(expectedResources) resources — \(String(format: "%.2f", progressPercentage * 100))%.")
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}
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}
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}
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@objc func offlinePackDidReceiveError(notification: NSNotification) {
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if let pack = notification.object as? MLNOfflinePack,
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let userInfo = try? jsonDecoder.decode(UserData.self, from: pack.context),
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let error = notification.userInfo?[MLNOfflinePackUserInfoKey.error] as? NSError
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{
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print("Offline pack “\(userInfo.name)” received error: \(error.localizedFailureReason ?? "unknown error")")
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}
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}
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@objc func offlinePackDidReceiveMaximumAllowedMapboxTiles(notification: NSNotification) {
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if let pack = notification.object as? MLNOfflinePack,
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let userInfo = try? jsonDecoder.decode(UserData.self, from: pack.context),
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let maximumCount = (notification.userInfo?[MLNOfflinePackUserInfoKey.maximumCount] as AnyObject).uint64Value
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{
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print("Offline pack “\(userInfo.name)” reached limit of \(maximumCount) tiles.")
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}
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}
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}
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```
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