Source: https://developers.woosmap.com/products/geofencing-sdk/flutter-plugin/guides/monitor-pois/

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# Monitor POIs with Geofence



## Create and monitor Geofences

Use region monitoring to determine when the user enters or leaves a geographic region.

Region monitoring (also known as Geofencing) combines awareness of the user's current location with awareness of the
user's proximity to locations that may be of interest. This region alerts your app when the user
enters or exits a geographical region. To mark a location of interest, you specify its latitude and longitude. To adjust
the proximity for the location, you add a radius. The latitude, longitude, and radius define a Geofence, creating a
circular area, or fence, around the location of interest. Find more details about Geofences in
[Geofence documentation](/products/geofencing-sdk/geofencing/)

## Adding and removing regions

Call `addRegion` method to add a region you want to monitor. Region type can be `circle` or `isochrone` only. This method will accept an object with following attributes:

* **regionId** - Id of the region
* **lat** - Latitude
* **lng** - Longitude
* **radius** - Radius in meters
* **type** - type of region

Create a custom circle region

``` dart
GeofenceRegion geofenceRegion = GeofenceRegion(
                                '7F91369E-467C-4CBD-8D41-6509815C4780', 
                                51.50998, 
                                -0.1337, 
                                180, 
                                RegionType.circle
                            );

Future<String?> returnVal = geofencingFlutterPlugin.addRegion(geofenceRegion);

returnVal.then((value){
    debugPrint(value!);
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});
```

Create a custom isochrone region

``` dart
GeofenceRegion geofenceRegion = GeofenceRegion(
                                '7F91369E-467C-4CBD-8D41-6509815C4780', 
                                51.50998, 
                                -0.1337, 
                                180, 
                                RegionType.isochrone
                            );

Future<String?> returnVal = geofencingFlutterPlugin.addRegion(geofenceRegion);

returnVal.then((value){
    debugPrint(value!);
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});
```

### Remove regions

Call `removeRegions` method to remove a region that you are monitoring. This method will accept the following parameter, and passing a null value will remove all regions.

* **regionId** - Id of the region
* **lat** - Latitude
* **lng** - Longitude
* **radius** - Radius in meters

``` dart
Future<String?> returnVal = geofencingFlutterPlugin.removeRegions('7F91369E-467C-4CBD-8D41-6509815C4780');

returnVal.then((value){
    debugPrint(value!);
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});
```

or

``` dart
Future<String?> returnVal = geofencingFlutterPlugin.removeRegions();

returnVal.then((value){
    debugPrint(value!);
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});
```

Whenever user crosses boundary of one of your app's registered regions, the system notifies your app.

On object `Region`, there is a boolean `didEnter` that indicates if you enter or exit region. You have
another boolean `fromPositionDetection` to know if the detection was launched by the position detection or by the system
detection.

Regions have an associated identifier, which this method uses to look up information related to region and perform
associated action.

### Get regions from the local database

Call `getRegions` method to get an array of Regions from local db.

``` dart
//Get a single region
Future<List<Region>?> returnVal = geofencingFlutterPlugin.getRegions(regionId);

returnVal.then((regions){
    if (regions != null){
        debugPrint('Regions: ${regions.length}');
    }else{
        debugPrint('Regions is null');
    }
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});

//Get all regions
Future<List<Region>?> returnVal = geofencingFlutterPlugin.getRegions();

returnVal.then((regions){
    if (regions != null){
        debugPrint('Regions: ${regions.length}');
    }else{
        debugPrint('Regions is null');
    }
}).catchError((error) {
    debugPrint('An error occurred: ${error.message}');
});
```

### Watch Region to track the region's events

Call `watchRegions` method to track Regions. This method will invoke a callback with the Region object.

``` dart
Future<String?> returnVal = geofencingFlutterPlugin.watchRegion();

returnVal.then((value){
    //Get the region stream    
    watchRegionStream = geofencingFlutterPlugin.getWatchRegionStream();
    //Listen to the stream
    watchRegionStream.listen((region){
        //Region updates will be received here.
        if (location != null) {
            debugPrint(region.eventName);
        } else {
            debugPrint("Region is null");
        }
    });
}).catchError((error) {
    debugPrint('An error occurred: $error');
});
```

To remove watch:

``` dart
Future<String?> returnVal = geofencingFlutterPlugin.clearRegionWatch();

returnVal.then((value){
    debugPrint(value!);
}).catchError((error) {
    debugPrint('An error occurred: $error');
});
```

## Create regions from Woosmap Search API assets

Region monitoring is a natural complement to Search requests performed on collected locations. Indeed, Search requests
help monitor approach to some assets you want to monitor. On every collected location you are aware of
surrounding assets (distance to them and even time if using Distance API request). You can then decide to monitor some
surrounding assets (e.g. the closest ones). Region monitoring is designed to do so.

To create a region around nearest result of the Search API request, choose a tracking profile with the tracking
properties `searchAPICreationRegionEnable` enable.

**Pre-requisites**  
You must define a Woosmap private API key to request the Woosmap Search API. How to set an Woosmap private key is explained
in
the [Initializing the plugin section.](/products/geofencing-sdk/flutter-plugin/guides/setup/#initializing-the-plugin)