Multiple geofencing in ionic - ionic-framework

Question

In my ionic project, I used geofence.
when I open the app in the region the notification is showing.
How can I view the notification only when crossing the border of the geofence.
and I used 3 fences(12Km.300m,50m).when in the range of 50m the app shows the three notification(notifications of three fences).
How i can show the only one notification when i am in the range of the 50m range condition.
in app.component.ts
constructor(public platform: Platform,
public statusBar: StatusBar,
...........) {
this.addGeofence();
}
private addGeofence() {
let fence = [{
id: '69ca1b88-6fbe-4e80-add-sd-4d3748-far',
latitude: 8.556498,
longitude: 76.881820,
radius: 12000,
transitionType: 1,
notification: {
id: 111111111,
title: 'Welcome ',
text: '12km range.',
openAppOnClick: true
}
},
{
id: '69ca1b88-6fbe-4e80-add-sd-4d3748-closevicinity',
latitude: 8.556498,
longitude: 76.881820,
radius: 300,
transitionType: 1,
notification: {
id: 222222222,
title: 'Welcome',
text: '300m range',
openAppOnClick: true
}
},
{
id: '69ca1b88-6fbe-4e80-add-sd-4d3748-near',
latitude: 8.556498,
longitude: 76.881820,
radius: 50,
transitionType: 1,
notification: {
id: 333333333,
title: 'Welcome',
text: '50m range',
openAppOnClick: true
}
},]

Answer 1

My suggestion: You can use the geolocation plugin of ionic to get the current location. Either use this to maybe check location once a minute, or use the background geolocation plugin to do so in background mode. For every location update you get, check whether you are in one of the radii of your geofences. You can use a library like turf to do the mathematics.
If you just want to be notified once you cross the border, save the geofence you were last in into the storage and each time you start the app check, whether the geofence changed.
Be careful though with location subscriptions and background modes as it might cost lots of battery.