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Geofence 1.1.0: Enter, Exit, and Dwell Inside Twenty Circular Regions

#dotnet #maui #geofence #nuvyntralabs

A depot app does not need a new GPS fix every few seconds. It needs to know when the device crosses a circle drawn around the yard.

Plugin.Maui.Geofence is that monitor. Version 1.1.0 is on nuget.org. You register named circular regions. The operating system reports enter, exit, and dwell. The list is written to app-private storage and registered again after the process dies.

This post is the walkthrough: how to register the plugin, add a region, read a transition, and which permissions the host still has to request.

What Geofence is

Geofence is a circular-region monitor for .NET MAUI on Android and iOS. MIT licensed. It targets net10.0, net10.0-android (API 21+), and net10.0-ios (15+). Mac Catalyst and Windows are not primary targets.

It does one job: answer when the user enters, exits, or dwells in up to 20 named regions.
Package Plugin.Maui.Geofence 1.1.0
Registration UseGeofence
Client IGeofence, or Geofence.Current
Platforms Android GeofencingClient, iOS CLCircularRegion
Source github.com/nuvyntralabs/Plugin.Maui.Geofence
Docs nuvyntralabs.github.io/packages/plugin-maui-geofence/

A current position, a tracking session, and reverse geocoding stay on Plugin.Maui.GeoLocator. Geofence does not draw a map.

Install and register 

dotnet add package Plugin.Maui.Geofence --version 1.1.0
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using Plugin.Maui.Geofence;

builder
    .UseMauiApp<App>()
    .UseGeofence(options =>
    {
        options.MaxRegions = 20;
        options.MinimumRadiusMeters = 50;
    });
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UseGeofence loads plugin.maui.geofence.regions.tsv from app data and re-registers those regions with the OS. Resolve IGeofence from dependency injection, or use Geofence.Current after registration. Calling Current before UseGeofence throws.

A radius of zero is replaced with DefaultRadiusMeters (100). A radius below MinimumRadiusMeters is rejected. Replacing a region that already has the same id does not consume another slot.

Add a region 

var result = await Geofence.Current.AddAsync(new GeofenceRegion
{
    Id = "depot",
    Latitude = 12.97,
    Longitude = 77.59,
    RadiusMeters = 150,
    NotifyOnEntry = true,
    NotifyOnExit = true,
    NotifyOnDwell = true,
    Dwell = TimeSpan.FromMinutes(5)
});

if (!result.Succeeded)
{
    // result.Status: Denied, LimitReached, InvalidRadius, InvalidId, NotSupported
}
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AddAsync returns a typed result. A missing location permission is Denied. Missing Play services is NotSupported. The 21st distinct id is LimitReached. An empty id is InvalidId. The call does not throw because the user said no.

Read a transition 

Geofence.Current.Transition += (_, args) =>
{
    // args.RegionId, args.Kind: Enter, Exit, or Dwell
};
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OS events queue until something subscribes to Transition. Attach the handler before you expect the first crossing, including crossings that happened while the process was down.

Android dwell uses GEOFENCE_TRANSITION_DWELL and a loitering delay of at least 60 seconds. iOS has no loitering delay. After enter, the plugin starts a timer and cancels it on exit.

Samples and tests can fire the same event without moving the device:

Geofence.Current.Raise(GeofenceTransitionKind.Enter, "depot");
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GetMonitoredAsync lists the regions still stored. RemoveAsync and RemoveAllAsync drop them from the store and from the OS.

Permissions the host still requests

The plugin does not prompt. Declare the usage strings, then request location yourself.

Android, in Platforms/Android/AndroidManifest.xml:

<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" />
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AddAsync needs fine location while the app is in use. Background transitions on Android 10+ also need ACCESS_BACKGROUND_LOCATION and the Play disclosure your listing already requires.

iOS, in Platforms/iOS/Info.plist:

<key>NSLocationWhenInUseUsageDescription</key>
<string>This app monitors geofences while you use it.</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>This app monitors geofences when the app is in the background.</string>
<key>UIBackgroundModes</key>
<array>
    <string>location</string>
</array>
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Background enter and exit on CLCircularRegion need Always authorization. Denied or Restricted comes back as Denied.

When something looks wrong

What you see What to do
InvalidId Id is blank. Every region needs a stable name.
InvalidRadius Radius is below MinimumRadiusMeters (50 by default).
LimitReached Twenty distinct ids are already monitored. Replace an id or remove one.
Denied Location permission is missing, or iOS authorization is Denied or Restricted.
NotSupported Play services are missing on Android.
No event after a crossing Nothing is subscribed to Transition yet, or background location was never granted.
Regions vanish after a kill UseGeofence was not called on the next launch, so the TSV was never re-registered.

Where Geofence sits next to the other tools

Need Tool
Enter, exit, and dwell for up to 20 circles Geofence — Plugin.Maui.Geofence
A current fix, a tracking session, reverse geocoding Plugin.Maui.GeoLocator
A measured offline trip against a vehicle meter GPSSensorTrackingService

Play GeofencingClient, CLCircularRegion, and Shiny are the usual native and community choices when the app already speaks one of those APIs. Geofence is the client when the same IGeofence has to run on Android and iOS, cap the list at 20, and reload it after process death.

Try it 

dotnet add package Plugin.Maui.Geofence --version 1.1.0
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Register UseGeofence, add one region with a radius of at least 50 meters, and subscribe to Transition before you leave the yard. samples/Plugin.Maui.Geofence.Sample requests location, adds a region, lists the persisted set, and simulates enter, exit, and dwell with Raise().

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