SwiftUI - Create geofence zone around user's location
This example shows the usage of the Mapbox Maps SDK for iOS Geofencing API to create a geofence zone for a radius around the user's location, updating its color based on events such as entering, dwelling, or leaving the geofence zone.
iOS Examples App Available
This example code is part of the Maps SDK for iOS Examples App, a working iOS project available on Github. iOS developers are encouraged to run the examples app locally to interact with this example in an emulator and explore other features of the Maps SDK.
See our Run the Maps SDK for iOS Examples App tutorial for step-by-step instructions.
GeofencingUserLocation.swift
import Foundation
import SwiftUI
@_spi(Experimental) import MapboxMaps
@_spi(Experimental) import MapboxCommon
/// This is an Example for Experimental API that is subject to change.
struct GeofencingUserLocation: View {
@State private var initialLocation: CLLocationCoordinate2D?
@ObservedObject private var geofencing = Geofencing()
private let initialLocationProvider = InitialLocationProvider()
var body: some View {
MapReader { proxy in
Map(initialViewport: .followPuck(zoom: 16)) {
Puck2D(bearing: .heading)
if let initialLocation = initialLocation {
GeofenceCircle(id: "circle", location: initialLocation, event: geofencing.lastEvent)
}
}
.onMapLoaded { _ in startGeofencing(proxy.location) }
}
.ignoresSafeArea()
}
func startGeofencing(_ locationManager: LocationManager?) {
geofencing.start {
initialLocationProvider.start(locationManager: locationManager) { initialLocation in
var feature = Feature(geometry: .geofenceCircle(initialLocation))
feature.identifier = .string("geofence-source-circle")
feature = feature.properties([GeofencingPropertiesKeys.dwellTimeKey: 1])
geofencing.add(feature: feature, onSuccess: { _initialLocation.wrappedValue = initialLocation })
}
}
}
}
private struct GeofenceCircle: MapStyleContent {
var id: String
var location: CLLocationCoordinate2D
var event: GeofenceEvent?
var body: some MapStyleContent {
GeoJSONSource(id: "geofence-source-\(id)")
.data(.geofenceCircle(location))
FillLayer(id: "geofence-layer-\(id)", source: "geofence-source-\(id)")
.fillColor(color(for: event))
.fillOpacity(0.5)
}
private func color(for event: GeofenceEvent?) -> UIColor {
switch event?.type {
case .none:
return .yellow
case .entry:
return .blue
case .exit:
return .red
case .dwell:
return .green
}
}
}
private final class InitialLocationProvider {
private var cancellables = Set<AnyCancelable>()
func start(locationManager: LocationManager?, _ onIntialLocation: @escaping (CLLocationCoordinate2D) -> Void) {
locationManager?.onLocationChange
.debounce(for: .seconds(0.5), scheduler: RunLoop.main)
.sink { [weak self] locations in
guard let location = locations.first else { return print("No locations received") }
onIntialLocation(location.coordinate)
self?.cancellables.removeAll()
}
.store(in: &cancellables)
}
}
private final class Geofencing: ObservableObject {
@Published var lastEvent: GeofenceEvent?
func start(_ completion: @escaping () -> Void) {
let geofencing = GeofencingFactory.getOrCreate()
geofencing.configure(options: GeofencingOptions()) { [weak self] result in
guard let self else { return }
/// Geofences are store in database on disk.
/// To make example isolated and synchronised with UI we try to delete existing feature from database.
geofencing.clearFeatures { result in
print("Clear features: \(result)")
geofencing.addObserver(observer: self) { result in print("Add observer: \(result)") }
completion()
}
}
}
func add(feature: Turf.Feature, onSuccess: @escaping () -> Void) {
let geofencing = GeofencingFactory.getOrCreate()
geofencing.addFeature(feature: feature) { result in
print("Add feature result: \(result)")
if case .success = result { onSuccess() }
}
}
func remove(featureId: String, completion: @escaping () -> Void) {
let geofencing = GeofencingFactory.getOrCreate()
geofencing.removeFeature(identifier: featureId) { result in
print("Remove feature result: \(result)")
completion()
}
}
}
extension Geofencing: GeofencingObserver {
func onEntry(event: GeofencingEvent) {
DispatchQueue.main.async { self.lastEvent = GeofenceEvent(type: .entry, feature: event.feature) }
}
func onDwell(event: GeofencingEvent) {
DispatchQueue.main.async { self.lastEvent = GeofenceEvent(type: .dwell, feature: event.feature) }
}
func onExit(event: GeofencingEvent) {
DispatchQueue.main.async { self.lastEvent = GeofenceEvent(type: .exit, feature: event.feature) }
}
func onError(error: GeofencingError) {}
func onUserConsentChanged(isConsentGiven: Bool) {}
}
private struct GeofenceEvent {
enum GeofenceEventType {
case entry
case dwell
case exit
}
var type: GeofenceEventType
var feature: Turf.Feature
}
private extension GeoJSONSourceData {
static func geofenceCircle(_ center: LocationCoordinate2D) -> GeoJSONSourceData {
.geometry(.geofenceCircle(center))
}
}
private extension Turf.Geometry {
static func geofenceCircle(_ center: LocationCoordinate2D) -> Turf.Geometry {
.polygon(Polygon(center: center, radius: 30, vertices: 64))
}
}
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