Geofence¶

class Geofence

A geofence definition for monitoring circular or polygon regions.

The SDK implements the native iOS and Android Geofencing APIs, extended with polygon support and a proximity-based infinite-geofencing system that overcomes the platform limits of 20 (iOS) and 100 (Android) simultaneous geofences.

Overview¶

Field	Required	Description
`identifier`	✅	Unique name for this geofence.
`latitude`	✅*	Center latitude (*omit for polygon geofences).
`longitude`	✅*	Center longitude (*omit for polygon geofences).
`radius`	✅*	Radius in meters (*omit for polygon geofences).
`notifyOnEntry`	—	Fire event on entry.
`notifyOnExit`	—	Fire event on exit.
`notifyOnDwell`	—	Fire event after loitering for `loiteringDelay` ms.
`vertices`	—	Polygon geofence vertices (replaces lat/lng/radius).
`extras`	—	Arbitrary key-value metadata posted with each event.

Warning

Both platforms require GeoConfig.locationAuthorizationRequest to be "Always". Geofencing does not work with "WhenInUse" only.

Adding geofences¶

Use BackgroundGeolocation.addGeofence for a single geofence, or BackgroundGeolocation.addGeofences for bulk inserts (approximately 10× faster than inserting individually).

If a geofence with the same identifier already exists in the database, it is replaced.

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "Home",
  radius: 200,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
  notifyOnExit: true,
  extras: { route_id: 1234 }
));

await BackgroundGeolocation.addGeofences([Geofence(
  identifier: "Home",
  radius: 200,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
), Geofence(
  identifier: "Work",
  radius: 200,
  latitude: 45.61921927,
  longitude: -73.71678582,
  notifyOnEntry: true
)]);

Listening for events¶

Subscribe to geofence transitions with BackgroundGeolocation.onGeofence. Subscribe to changes in the actively monitored set with BackgroundGeolocation.onGeofencesChange.

BackgroundGeolocation.onGeofence((GeofenceEvent event) {
  print('[onGeofence] ${event.identifier} ${event.action}');
});

BackgroundGeolocation.onGeofencesChange((GeofencesChangeEvent event) {
  final on = event.on;   // newly activated geofences
  final off = event.off; // deactivated geofence identifiers

  for (final geofence in on) {
    print('[geofencesChange] activated: ${geofence.identifier}');
  }
  for (final identifier in off) {
    print('[geofencesChange] deactivated: ${identifier}');
  }
});

Note

When all geofences are removed, BackgroundGeolocation.onGeofencesChange fires with empty arrays for both on and off.

Polygon geofencing¶

The SDK supports polygon geofences of any shape via the vertices field. Polygon geofencing is sold as a separate add-on but is fully functional in DEBUG builds.

When defining a polygon geofence, omit latitude, longitude, and radius — the SDK calculates the minimum enclosing circle automatically from the polygon geometry.

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "Park",
  notifyOnEntry: true,
  notifyOnExit: true,
  vertices: [
    [45.518947279987714, -73.6049889209514],
    [45.5182711292279,   -73.60338649600598],
    [45.517082240237634, -73.60432670908212],
    [45.51774871402813,  -73.60604928622278]
  ]
));

Infinite geofencing¶

The SDK stores all geofences in its database and uses a geospatial query to activate only the nearest geofences within GeoConfig.geofenceProximityRadius, staying within the platform limit. As the device moves, the active set is periodically refreshed.

The minimum GeoConfig.geofenceProximityRadius is enforced at 1000 meters.
Geofences within the radius (green in the diagram below) are actively monitored.
Geofences outside the radius (grey) remain in the database but are dormant.

Removing geofences¶

Geofences persist in the SDK's database until explicitly removed. If AppConfig.stopOnTerminate is false and AppConfig.startOnBoot is true, geofences continue to be monitored across app termination and device reboots.

await BackgroundGeolocation.removeGeofence("Home");

await BackgroundGeolocation.removeGeofences();

final geofences = await BackgroundGeolocation.geofences;
print('[getGeofences] ${geofences}');

Geofences-only mode¶

Call BackgroundGeolocation.startGeofences instead of BackgroundGeolocation.start to monitor geofences without continuous location tracking. Use GeoConfig.geofenceModeHighAccuracy to improve event responsiveness at the cost of higher power usage.

The SDK can switch between full tracking and geofences-only mode at any time by calling the corresponding start method.

BackgroundGeolocation.onGeofence((GeofenceEvent event) {
  print('[onGeofence] ${event}');
});

await BackgroundGeolocation.ready(Config(
  http: HttpConfig( url: "https://your.server.com/geofences", autoSync: true ),
  geolocation: GeoConfig( geofenceModeHighAccuracy: true )
));
BackgroundGeolocation.startGeofences();

Examples¶

BackgroundGeolocation.onGeofence((GeofenceEvent event) {
  if (event.identifier == "DANGER_ZONE") {
    if (event.action == "ENTER") {
      // Entering the zone — switch to full location tracking.
      BackgroundGeolocation.start();
    } else if (event.action == "EXIT") {
      // Exiting the zone — return to geofences-only mode.
      BackgroundGeolocation.startGeofences();
    }
  }
});

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "DANGER_ZONE",
  radius: 1000,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
  notifyOnExit: true,
));

await BackgroundGeolocation.ready(Config(
  geolocation: GeoConfig(
    desiredAccuracy: DesiredAccuracy.high,
    distanceFilter: 10.0,
  ),
  http: HttpConfig( url: "https://your.server.com/locations", autoSync: true )
));
BackgroundGeolocation.startGeofences();

Single geofence¶

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "Home",
  radius: 200,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
  notifyOnExit: true,
  extras: { route_id: 1234 }
));

Multiple geofences¶

await BackgroundGeolocation.addGeofences([Geofence(
  identifier: "Home",
  radius: 200,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
), Geofence(
  identifier: "Work",
  radius: 200,
  latitude: 45.61921927,
  longitude: -73.71678582,
  notifyOnEntry: true
)]);

Polygon geofence¶

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "Park",
  notifyOnEntry: true,
  notifyOnExit: true,
  vertices: [
    [45.518947279987714, -73.6049889209514],
    [45.5182711292279,   -73.60338649600598],
    [45.517082240237634, -73.60432670908212],
    [45.51774871402813,  -73.60604928622278]
  ]
));

Remove a single geofence¶

await BackgroundGeolocation.removeGeofence("Home");

Remove all geofences¶

await BackgroundGeolocation.removeGeofences();

Fetch all stored geofences¶

final geofences = await BackgroundGeolocation.geofences;
print('[getGeofences] ${geofences}');

Geofences-only mode¶

BackgroundGeolocation.onGeofence((GeofenceEvent event) {
  print('[onGeofence] ${event}');
});

await BackgroundGeolocation.ready(Config(
  http: HttpConfig( url: "https://your.server.com/geofences", autoSync: true ),
  geolocation: GeoConfig( geofenceModeHighAccuracy: true )
));
BackgroundGeolocation.startGeofences();

Toggle between location tracking and geofences-only mode¶

BackgroundGeolocation.onGeofence((GeofenceEvent event) {
  if (event.identifier == "DANGER_ZONE") {
    if (event.action == "ENTER") {
      // Entering the zone — switch to full location tracking.
      BackgroundGeolocation.start();
    } else if (event.action == "EXIT") {
      // Exiting the zone — return to geofences-only mode.
      BackgroundGeolocation.startGeofences();
    }
  }
});

BackgroundGeolocation.addGeofence(Geofence(
  identifier: "DANGER_ZONE",
  radius: 1000,
  latitude: 45.51921926,
  longitude: -73.61678581,
  notifyOnEntry: true,
  notifyOnExit: true,
));

await BackgroundGeolocation.ready(Config(
  geolocation: GeoConfig(
    desiredAccuracy: DesiredAccuracy.high,
    distanceFilter: 10.0,
  ),
  http: HttpConfig( url: "https://your.server.com/locations", autoSync: true )
));
BackgroundGeolocation.startGeofences();

Members¶

entryState¶

int? entryState

Current entry state of the geofence.

Value	State
`0`	Outside
`1`	Inside

extras¶

Map<String, dynamic>? extras

Arbitrary key-value metadata attached to each geofence event and included in the payload posted to HttpConfig.url.

hits¶

int? hits

Number of times this geofence has been triggered since it was added.

identifier¶

String identifier

Unique identifier for this geofence.

Used to reference the geofence in events and removal calls. Adding a geofence with an identifier that already exists replaces the existing one.

latitude¶

double? latitude

Latitude of the circular geofence center.

Omit when defining a polygon geofence via vertices — the SDK calculates the center automatically.

loiteringDelay¶

int? loiteringDelay

Minimum time in milliseconds the device must remain inside the geofence before a notifyOnDwell event fires. Default 0.

longitude¶

double? longitude

Longitude of the circular geofence center.

Omit when defining a polygon geofence via vertices — the SDK calculates the center automatically.

notifyOnDwell¶

bool? notifyOnDwell

Fire a GeofenceEvent when the device has remained inside this geofence for loiteringDelay milliseconds.

notifyOnEntry¶

bool? notifyOnEntry

Fire a GeofenceEvent when the device enters this geofence.

notifyOnExit¶

bool? notifyOnExit

Fire a GeofenceEvent when the device exits this geofence.

radius¶

double? radius

Radius of the circular geofence in meters.

Omit when defining a polygon geofence via vertices — the SDK calculates the enclosing radius automatically.

Warning

The minimum reliable radius is 200 meters. Below this threshold, geofences may not trigger reliably on either platform.

Apple documents this explicitly:

"For testing purposes, you can assume that the minimum distance is approximately 200 meters."

stateUpdatedAt¶

double? stateUpdatedAt

Epoch timestamp in seconds of the last geofence transition.

vertices¶

List<List<double>>? vertices

Polygon geofence vertices as [[lat, lng], ...] pairs.

When provided, the geofence is treated as a polygon rather than a circle. Omit latitude, longitude, and radius — the SDK solves the minimum enclosing circle from the vertex geometry and registers that as the native circular geofence.

When the device enters the enclosing circle, the SDK begins C++ hit-testing against the polygon at high frequency. When it exits the circle, polygon monitoring ceases.

Note

Polygon geofencing is sold as a separate add-on but is fully functional in DEBUG builds.

BackgroundGeolocation.addGeofence(Geofence(
  identifier: 'Home',
  notifyOnEntry: true,
  notifyOnExit: true,
  vertices: [
    [45.518947279987714, -73.6049889209514],  // <-- [lat, lng]
    [45.5182711292279, -73.60338649600598],
    [45.517082240237634, -73.60432670908212],
    [45.51774871402813, -73.60604928622278]
  ]
));