React Native expo project error with geolocation or MapView on android

Question

So:

I have React Native project made trough Expo. It has couple of views, airbnb mapView and stuff like that. It was previously pure react native project (Made before create-react-native-app was even a thing) and I lately moved it to expo. Almost everything works fine. The transformation to expo was perfectly fine for iOS and everything works as expected on that side. BUT i get really weird error when trying to launch the app on android phone.

Attempt to invoke interface method 'boolean abi20_0_0.com.facebook.react.bridge.ReadableMap.hasKey(java.lang.String)' on a null object reference

I think it has something to do with the actual process of finding the location not really the mapView, but the only thing i changed was:

import MapView from 'react-native-maps'; to import { MapView } from 'expo';

This is the actual code used to find location:

componentDidMount() {
    navigator.geolocation.getCurrentPosition(
            (position) => {
            this.setState({
                    region: {
                        latitude: position.coords.latitude,
                        longitude: position.coords.longitude,
                        latitudeDelta: LATITUDE_DELTA,
                        longitudeDelta: LONGITUDE_DELTA
                    },
                    lat : position.coords.latitude,
                    lon : position.coords.longitude,
                    cords : {
                          latitude: position.coords.latitude,
                        longitude: position.coords.longitude,
                }
                });
            },
            (error) => alert(error.message),
        {enableHighAccuracy: true, timeout: 20000, maximumAge: 1000}
    );

    this.watchID = navigator.geolocation.watchPosition(
        (position) => {
            this.setState({
                    cords : {
                        latitude: position.coords.latitude,
                        longitude: position.coords.longitude,
                    },
                    lat : position.coords.latitude,
                    lon : position.coords.longitude,
                });
        });
 }

It still works normally on the old android version without expo and it works on the new iOS version made with expo.

package.json depencies

"dependencies": {
    "expo": "^20.0.0",
    "firebase": "^4.3.0",
    "react": "16.0.0-alpha.12",
    "react-native": "https://github.com/expo/react-native/archive/sdk-20.0.0.tar.gz",
    "react-navigation": "^1.0.0-beta.11"
  }

I founded one other question on this exactly same problem: watchPosition fails with react native expo He had ended up to the same conclusion as I but had very little info on his question and no answers/comments so I decided to make my own question.

I tried with 2 real devices and emulator. On iOS only real device. Both Standalone and the expo version on every device/emulator. The older version without expo worked on every single one of them — Nipatiitti

zino zino · Accepted Answer · 2018-03-07T14:09:33

Pass an empty options object as the 3rd argument to watchPosition on Android.

https://github.com/facebook/react-native/issues/14580

React Native expo project error with geolocation or MapView on android

1 Answers