Native Geofence

Battery efficient Flutter geofencing plugin that uses native iOS and Android APIs.

What is geofencing?

A way for your app to be alerted when the user enters or exits a geographical region. You might use geofences to perform location-related tasks. For example, to setup reminders when the user leaves their house.

What are the plugin requirements?

iOS 14+ and Android API 29+. You will also need to obtain background location permission from the user.

Features

• Uses CLLocationManager on iOS and GeofencingClient on Android
• Create geofences
• Be notified of enter/exit/dwell events
• Works when the application is:
  • In the foreground
  • In the background
  • Terminated
• Geofences are re-registered after device reboot
• Fetch currently registered geofences
• Android Run foreground service to handle geofence event

Setup

<!-- Used by plugin: native_geofence -->
<receiver android:name="com.chunkytofustudios.native_geofence.receivers.NativeGeofenceBroadcastReceiver"
          android:exported="true"/>
<receiver android:name="com.chunkytofustudios.native_geofence.receivers.NativeGeofenceRebootBroadcastReceiver"
          android:exported="true">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"></action>
    </intent-filter>
</receiver>
<service android:name="com.chunkytofustudios.native_geofence.NativeGeofenceForegroundService"
          android:permission="android.permission.BIND_JOB_SERVICE" android:exported="true"/>

<!-- Used by plugin: native_geofence -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<uses-permission android:name="android.permission.WAKE_LOCK"/>

<key>NSLocationWhenInUseUsageDescription</key>
<string>USER_VISIBLE_STRING__DESCRIBE_HOW_YOUR_APP_USES_LOCATION.</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>USER_VISIBLE_STRING__DESCRIBE_HOW_YOUR_APP_USES_BACKGROUND_LOCATION.</string>
<key>UIBackgroundModes</key>
<array>
  <string>location</string>
</array>

import native_geofence

// Used by plugin: native_geofence
NativeGeofencePlugin.setPluginRegistrantCallback { registry in
    GeneratedPluginRegistrant.register(with: registry)
}

#import <native_geofence/NativeGofencePlugin.h>

void registerPlugins(NSObject<FlutterPluginRegistry>* registry) {
  [GeneratedPluginRegistrant registerWithRegistry:registry];
}

// Used by plugin: native_geofence
[NativeGofencePlugin setPluginRegistrantCallback:registerPlugins];

Usage

Initialize the plugin

Before accesing any methods ensure you initialize the plugin:

await NativeGeofenceManager.instance.initialize();

Obtain permissions

This plugin does not deal with obtaining permissions from the user. Please use a 3rd party plugin, such as permission_handler for that.

As noted in the setup section you will need to obtain the following permissions:

• Permission.location
• Permission.locationAlways: if you want to be notified of geofence events when your app isn't running

Create geofence

First, define your geofence parameters using the Geofence class, for example:

Note: The ID must be unqiue. Please see the API reference for details.

final zone1 = Geofence(
  id: 'zone1',
  location: Location(latitude: 40.75798, longitude: -73.98554), // Times Square
  radiusMeters: 500,
  triggers: {
    GeofenceEvent.enter,
    GeofenceEvent.exit,
    GeofenceEvent.dwell,
  },
  iosSettings: IosGeofenceSettings(
    initialTrigger: true,
  ),
  androidSettings: AndroidGeofenceSettings(
    initialTriggers: {GeofenceEvent.enter},
    expiration: const Duration(days: 7),
    loiteringDelay: const Duration(minutes: 5),
    notificationResponsiveness: const Duration(minutes: 5),
  ),
);

Next, create a top-level function that has the @pragma('vm:entry-point') annotation; this will act as your geofence callback/handler:

Note: You can (optional) specify a unique callback function for each geofence.

@pragma('vm:entry-point')
Future<void> geofenceTriggered(GeofenceCallbackParams params) async {
  debugPrint('Geofence triggered with params: $params');
}

Finally, create the geofence:

await NativeGeofenceManager.instance.createGeofence(zone1, geofenceTriggered);

Android only Foreground work

If you need to access certain APIs or run a long job in your geofence callback you can promote the runner to a foreground service. You have access to the following functions when running within a geofence callback:

NativeGeofenceBackgroundManager.instance.promoteToForeground();
// Do a lot of work or access live location?
NativeGeofenceBackgroundManager.instance.demoteToBackground();

Note: Most tasks that complete in a few seconds, such as sending a notification, don't require your callback to run in a foreground service.

Warning: This functionality is not well tested. Please report any bugs you find.

Get registered geofences

You can see which geofences are currently active using:

final List<ActiveGeofence> myGeofences = await NativeGeofenceManager.instance.getRegisteredGeofences();
print('There are ${myGeofences.length} active geofences.')

Remove geofence

You have multiple options to stop listenning for geofence events:

// Remove a single geofence:
await NativeGeofenceManager.instance.removeGeofenceById('zone1');
// Remove all geofences:
await NativeGeofenceManager.instance.removeAllGeofences();

Error handling

All errors thrown by this plugin are wrapped in NativeGeofenceException.

Each exception will contain an error code, please see the API reference a description of each of them.

Ensure you catch this exception and take the neccesary action. For example you might:

try {
  await NativeGeofenceManager.instance.createGeofence(zone1, geofenceTriggered);
} on NativeGeofenceException catch (e) {
  if (e.code == NativeGeofenceErrorCode.missingLocationPermission) {
    print('Did the user grant us the location permission yet?')
    return
  }
  if (e.code == NativeGeofenceErrorCode.pluginInternal) {
    print('Some internal error occured: message=${e.message}, detail=${e.details}, stackTrace=${e.stacktrace}')
    return
  }
  // Handle other cases.
}

Example

The provided example app demonstrates how to request permissions, register geofences, and send notifications when geofence events occur.

Prior art

This plugin is based off of bkonyi/FlutterGeofencing and uses code snippets from flutter_workmanager. It was inspired by 525k.io's geofence_foreground_service plugin.

Contributing

Please file any issues, bugs, or feature requests at GitHub.

Pull requests are welcome.

Future work

• Android: Allow customizing the notification shown when a geofence callback upgrades to a foreground service.
• Android: Allow customizing the wake lock duration when foreground service is launched.
• Other ideas?

Known Issues

• iOS: After reboot, the first geofence event is triggered twice, one immediatly after the other. We recommend checking the last trigger time of a geofence in your app to discard duplicates.
• Android: The emulator does not trigger geofence events if there are no apps accessing the device location. This is an emulator issue. As a workaround you can open Google Maps to get a location fix which will in turn trigger the geofence.

Author

This plugin is developed by Chunky Tofu Studios.

You can support us by checking out our apps!

For commercial support please reach out to hello@chunkytofustudios.com.