Stop Offline MapBox Map re-downloading - ios

Question

I am using MapBox to download an offline map. So that my user has access to a specific area when they go travelling.
Using the MapBox Offline documentation, it appears that the MapBox Map always tries to download (re-download) whenever there is a connection.
How do I set up my MapBox so that it performs a check in storage to see if the map has been downloaded?
func startOfflinePackDownload() {
let region = MGLTilePyramidOfflineRegion(styleURL: mapView.styleURL, bounds: mapView.visibleCoordinateBounds, fromZoomLevel: mapView.zoomLevel, toZoomLevel: 13)
let userInfo = ["name": "My Offline Pack"]
let context = NSKeyedArchiver.archivedData(withRootObject: userInfo)
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()
}
}
I found the below code to check to see if the download already exists... So this would go at the start of my 'startOfflinePackDownload()' function above.
However, the newer version of MapBox doesn't recognise the code. Is someone able to help me on this please?
MGLOfflineStorage.sharedOfflineStorage().getPacksWithCompletionHandler { (packs, error) in guard error == nil else {
return
}
for pack in packs {
let userInfo = NSKeyedUnarchiver.unarchiveObjectWithData(pack.context) as! [String: String]
if userInfo["name"] == "My Offline Pack" {
// allready downloaded
return
}
}

Answer 1

See the mapbox Doc , MGLOfflinePackStateUnknown = 0 means the the tiles is already downloaded, so we can check the Offline pack state likewise :
Code is in Objective c , You can convert to swift
-(void)mapViewDidFinishLoadingMap:(MGLMapView *)mapView {
NSArray *arrTiles = MGLOfflineStorage.sharedOfflineStorage.packs;
if (arrTiles.count==0) {
[self startOfflinePackDownload];
}
for (MGLOfflinePack *downloadPack in arrTiles) {
NSLog(#"title: %#",downloadPack.region.description );
switch (downloadPack.state) {
case MGLOfflinePackStateUnknown:
[downloadPack requestProgress];
break;
case MGLOfflinePackStateComplete:
break;
case MGLOfflinePackStateInactive:
[downloadPack resume];
break;
case MGLOfflinePackStateActive:
[self startOfflinePackDownload];
break;
case MGLOfflinePackStateInvalid:
// NSAssert(NO, #"Invalid offline pack at index path %#", indexPath);
break;
}
}
}

Answer 2

You should use MGLOfflineStorage.shared().packs, note that use this method only after map is fully loaded. Implement MGLMapViewDelegate method:
func mapViewDidFinishLoadingMap(_ mapView: MGLMapView) {
print(MGLOfflineStorage.shared().packs)
}
This code snippet will print all your packs, that currently stored on device. Don't do that in viewDidLoad or viewWillAppear methods, MGLOfflineStorage.shared().packs will return nil.
After you receive your packs you can iterate through them and choose that pack what your need to resume downloading or deleting it from offline storage
UPDATE
Save somewhere in code your content pack name of your downloading region and Bool variable to determine if your pack is already downloaded
let packageName = "YourPackageName"
var isPackageNameAlreadyDownloaded = false
Func below checks if packageName is already downloaded:
func downloadPackage() {
if let packs = MGLOfflineStorage.shared().packs {
if packs.count > 0 {
// Filter all packs that only have name
let filteredPacks = packs.filter({
guard let context = NSKeyedUnarchiver.unarchiveObject(with: $0.context) as? [String:String] else {
print("Error retrieving offline pack context")
return false
}
let packTitle = context["name"]!
return packTitle.contains("(Data)") ? false : true
})
// Check if filtered packs contains your downloaded region
for pack in filteredPacks {
var packInfo = [String:String]()
guard let context = NSKeyedUnarchiver.unarchiveObject(with: pack.context) as? [String:String] else {
print("Error retrieving offline pack context")
return
}
// Recieving packageName
let packTitle = context["name"]!
if packTitle == packageName {
// Simply prints how download progress
print("Expected: \(pack.progress.countOfResourcesExpected); Completed: \(pack.progress.countOfBytesCompleted)")
print("Tile bytes completed: \(pack.progress.countOfTileBytesCompleted); Tiles Completed: \(pack.progress.countOfTilesCompleted)")
// If package isn't fully downloaded resume progress. If it downloaded - it'll check and won't redownload it
pack.resume()
isPackageNameAlreadyDownloaded = true
break
} else {
// This is another region
}
}
}
}
// If region is downloaded - return
if isPackageNameAlreadyDownloaded {
return
}
// if not - create region, map style url (which you recieve from MapBox Styler
let region = MGLTilePyramidOfflineRegion(styleURL: URL(string: YourMapStyleUrl)!, bounds: YourBoundaries, fromZoomLevel: 12, toZoomLevel: 16.5)
// Save packageName in Library and archive in package context.
let userInfo = ["name": packageName]
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()
print(MGLOfflineStorage.shared().packs)
// Shows the download progress in logs
print(pack!.progress)
}
}