Is it possible in react-native to execute a background task with monitoring GPS position (without running the whole app in the background), even if the phone is locked? I want to show some information (notification) onscreen when the phone will be in some position.
I need to declare the subject of a project in my studies, but I don't know if it's possible to implement this functionality.
It most certainly is... if you have only one given position (Or fewer than 20 positions) what you'd be best using is CoreLocation's geofencing APIs!
You can set up a region like so:
if CLLocationManager.isMonitoringAvailable(for: CLCircularRegion.self) {
// Register the region.
let region = CLCircularRegion(
center: center,
radius: maxDistance, identifier: identifier
)
region.notifyOnEntry = true
locationManager.startMonitoring(for: region)
}
(Assuming you have already requested and checked the user's location permissions)!
Your app will then get launched in the background whenever a region monitoring event occurs, so you must make sure to setup a new CLLocationManager and give it a delegate to receive the updates in your application(_application:didFinishLaunchingWithOptions) function!
You can then use the delegate callbacks to trigger a local notification.
There is a slight caveat here, that this won't work if the user has disabled background app refresh for your app!
Luck, there's already a react-native library that allows you to setup these regions: https://github.com/martijndeh/react-native-region-monitor. Unfortunately I do think it will launch your JavaScript app fully (in the background of course) when a notification comes through, but that's not too big an issue.
There may also be info on the GitHub provided for how to implement this on Android too!