Download an offline map

import Mapbox
 
class ViewController: UIViewController, MGLMapViewDelegate {
var mapView: MGLMapView!
var progressView: UIProgressView!
 
override func viewDidLoad() {
super.viewDidLoad()
 
mapView = MGLMapView(frame: view.bounds, styleURL: MGLStyle.darkStyleURL)
mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
mapView.tintColor = .gray
mapView.delegate = self
view.addSubview(mapView)
 
mapView.setCenter(CLLocationCoordinate2D(latitude: 22.27933, longitude: 114.16281),
zoomLevel: 13, animated: false)
 
// Setup offline pack notification handlers.
NotificationCenter.default.addObserver(self, selector: #selector(offlinePackProgressDidChange), name: NSNotification.Name.MGLOfflinePackProgressChanged, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(offlinePackDidReceiveError), name: NSNotification.Name.MGLOfflinePackError, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(offlinePackDidReceiveMaximumAllowedMapboxTiles), name: NSNotification.Name.MGLOfflinePackMaximumMapboxTilesReached, object: nil)
}
 
func mapViewDidFinishLoadingMap(_ mapView: MGLMapView) {
// Start downloading tiles and resources for z13-14.
startOfflinePackDownload()
}
 
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
 
// When leaving this view controller, suspend offline downloads.
guard let packs = MGLOfflineStorage.shared.packs else { return }
for pack in packs {
if let userInfo = NSKeyedUnarchiver.unarchiveObject(with: pack.context) as? [String: String] {
print("Suspending download of offline pack: “\(userInfo["name"] ?? "unknown")”")
}
pack.suspend()
}
}
 
deinit {
// Remove offline pack observers.
print("Removing offline pack notification observers")
NotificationCenter.default.removeObserver(self)
}
 
func startOfflinePackDownload() {
// Create a region that includes the current viewport and any tiles needed to view it when zoomed further in.
// Because tile count grows exponentially with the maximum zoom level, you should be conservative with your `toZoomLevel` setting.
let region = MGLTilePyramidOfflineRegion(styleURL: mapView.styleURL, bounds: mapView.visibleCoordinateBounds, fromZoomLevel: mapView.zoomLevel, toZoomLevel: 14)
 
// Store some data for identification purposes alongside the downloaded resources.
let userInfo = ["name": "My Offline Pack"]
let context = NSKeyedArchiver.archivedData(withRootObject: userInfo)
 
// Create and register an offline pack with the shared offline storage object.
 
MGLOfflineStorage.shared.addPack(for: region, withContext: context) { (pack, error) in
guard error == nil else {
// The pack couldn’t be created for some reason.
print("Error: \(error?.localizedDescription ?? "unknown error")")
return
}
 
// Start downloading.
pack!.resume()
}
 
}
 
// MARK: - MGLOfflinePack notification handlers
 
@objc func offlinePackProgressDidChange(notification: NSNotification) {
// Get the offline pack this notification is regarding,
// and the associated user info for the pack; in this case, `name = My Offline Pack`
if let pack = notification.object as? MGLOfflinePack,
let userInfo = NSKeyedUnarchiver.unarchiveObject(with: pack.context) as? [String: String] {
let progress = pack.progress
// or notification.userInfo![MGLOfflinePackProgressUserInfoKey]!.MGLOfflinePackProgressValue
let completedResources = progress.countOfResourcesCompleted
let expectedResources = progress.countOfResourcesExpected
 
// Calculate current progress percentage.
let progressPercentage = Float(completedResources) / Float(expectedResources)
 
// Setup the progress bar.
if progressView == nil {
progressView = UIProgressView(progressViewStyle: .default)
let frame = view.bounds.size
progressView.frame = CGRect(x: frame.width / 4, y: frame.height * 0.75, width: frame.width / 2, height: 10)
view.addSubview(progressView)
}
 
progressView.progress = progressPercentage
 
// If this pack has finished, print its size and resource count.
if completedResources == expectedResources {
let byteCount = ByteCountFormatter.string(fromByteCount: Int64(pack.progress.countOfBytesCompleted), countStyle: ByteCountFormatter.CountStyle.memory)
print("Offline pack “\(userInfo["name"] ?? "unknown")” completed: \(byteCount), \(completedResources) resources")
} else {
// Otherwise, print download/verification progress.
print("Offline pack “\(userInfo["name"] ?? "unknown")” has \(completedResources) of \(expectedResources) resources — \(String(format: "%.2f", progressPercentage * 100))%.")
}
}
}
 
@objc func offlinePackDidReceiveError(notification: NSNotification) {
if let pack = notification.object as? MGLOfflinePack,
let userInfo = NSKeyedUnarchiver.unarchiveObject(with: pack.context) as? [String: String],
let error = notification.userInfo?[MGLOfflinePackUserInfoKey.error] as? NSError {
print("Offline pack “\(userInfo["name"] ?? "unknown")” received error: \(error.localizedFailureReason ?? "unknown error")")
}
}
 
@objc func offlinePackDidReceiveMaximumAllowedMapboxTiles(notification: NSNotification) {
if let pack = notification.object as? MGLOfflinePack,
let userInfo = NSKeyedUnarchiver.unarchiveObject(with: pack.context) as? [String: String],
let maximumCount = (notification.userInfo?[MGLOfflinePackUserInfoKey.maximumCount] as AnyObject).uint64Value {
print("Offline pack “\(userInfo["name"] ?? "unknown")” reached limit of \(maximumCount) tiles.")
}
}
 
}