Limit amount of tile requests based on quota

YuriReis

I'm attempting to restrict the number of fired requests that we make to our remote tile provider.

Currently, we're using a AGSArcGISTiledLayer, inited with the URL of the provider. This works fine and I can see all the tiles appearing in the layer. I noticed that after the initial configuration, the SDK requests tiles automatically, based on the map's view port. How should I go about restricting these tile requests for this specific layer? 

Here is the code we have so far:

let map = AGSMap(basemapType: .navigationVector, 
                 latitude: latitude, 
                 longitude: longitude, 
                 levelOfDetail: 18)
mapView.map = map
let tiledLayer = AGSArcGISTiledLayer(url: URL(string: urlPath)!)
tiledLayer.minScale = 8000
mapView.map?.operationalLayers.add(tiledLayer)

I tried including a tileRequestHandler to maybe cancel the tile request before it begins, but it isn't called at all.

Using ArcGIS-Runtime-SDK-iOS (100.7.1).

Any ideas? Thank you!

Nicholas-Furness

Out of interest, what do you want the behavior to be when you hit your limiting criteria?

But you should be creating an AGSImageTiledLayer with an AGSTileInfo and a full extent. See AGSImageTiledLayer(CustomImageTiledLayer). Since you're working with an ArcGIS service for the layer, you can just lift that directly from the service. This code works well (you should probably modify the tileCount code - I've put no effort into making it thread safe and am relying on the tileRequestHandler being called on the main queue to force sequential access to tileCount) :

 

 

import UIKit
import ArcGIS

class ViewController: UIViewController {

    @IBOutlet weak var mapView: AGSMapView!
    
    let layerURL = URL(string: "https://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer")!
    
    var tileCount = 0
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        let metadataLayer = AGSArcGISTiledLayer(url: layerURL)
        
        metadataLayer.load { [weak self] (error) in
            guard let self = self else { return }
            
            if let error = error {
                print("Error loading layer: \(error.localizedDescription)")
                return
            }

            if let tileInfo = metadataLayer.tileInfo,
               let fullExtent = metadataLayer.fullExtent {
                
                let customLayer = AGSImageTiledLayer(tileInfo: tileInfo, fullExtent: fullExtent)

                // This highlights how tiles are not retrieved
                customLayer.noDataTileBehavior = .blank
                
                customLayer.tileRequestHandler = { [weak self, layerURL = self.layerURL] tileKey in
                    guard let self = self else { return }
                    
                    guard self.tileCount < 4 else {
                        // Note, the first tile (global tile at zoom 0) might not be displayed as it
                        // is superceded by tiles at zoom level 1.
                        customLayer.respondWithNoDataTile(for: tileKey)
                        return
                    }

                    self.tileCount += 1
                    
                    let tileUrl = layerURL
                        .appendingPathComponent("tile")
                        .appendingPathComponent("\(tileKey.level)")
                        .appendingPathComponent("\(tileKey.row)")
                        .appendingPathComponent("\(tileKey.column)")
                    
//                    print("\(self.tileCount) \(tileUrl.path)")
                    
                    // Piggy back on ArcGIS Authentication with AGSRequestOperation
                    let tileOp = AGSRequestOperation(url: tileUrl)
                    tileOp.registerListener(customLayer) { [weak customLayer] (tileData, error) in
                        guard let customLayer = customLayer else { return }
                        guard let tileData = tileData as? Data else {
                            customLayer.respondWithNoDataTile(for: tileKey)
                            return
                        }
                        customLayer.respond(with: tileKey, data: tileData, error: error)
                    }
                    AGSOperationQueue.shared().addOperation(tileOp)
                }
                
                let basemap = AGSBasemap(baseLayer: customLayer)
                self.mapView.map = AGSMap(basemap: basemap)
            }
        }
    }
}