react native GeoLocation null reference error

Question

I am using the below code to try to get my current location:

componentDidMount() {
    this.watchID = navigator.geolocation.watchPosition((position) => {
        let region = {
            latitude:       position.coords.latitude,
            longitude:      position.coords.longitude,
            latitudeDelta:  0.00922*1.5,
            longitudeDelta: 0.00421*1.5,
            enableHighAccuracy: true
        }
        this.onRegionChange(region, region.latitude, region.longitude);
    });
}

And I am getting:

Attempt to invoke interface method 'boolean abi26_0_0.com.facebook.react.bridge.ReadableMap.hasKey(java.lang.String)' on a null object reference

Which is triggering on this line:

this.watchID = navigator.geolocation.watchPosition((position) => {

Is there something I need to import for this to work maybe? I can't find anything online about this.

Answer 1

I finally nailed it after many hours of searching.

If you are using CRNA, like me (create-react-native-app was the way you built your app), you need to fulfill all parts of the function call. These are (success, error, options). The code below is how to fulfill all these parts and remove this error.

componentDidMount() {
this.watchId = navigator.geolocation.watchPosition(
  (position) => {
    this.setState({
      latitude: position.coords.latitude,
      longitude: position.coords.longitude,
      error: null,
    });
  },
  (error) => this.setState({ error: error.message }),
  { enableHighAccuracy: true, timeout: 20000, maximumAge: 1000, distanceFilter: 10 },
);
}