Expo gists

location-background-update

import React from "react";
import { StyleSheet, Text, View, Button } from "react-native";
import { Location, Permissions, TaskManager } from "expo";

const MY_LOCATION_TASK = "MY_LOCATION_TASK";

export default class App extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      positions: []
    };
  }

  async startTracking() {
    let { status } = await Permissions.askAsync(Permissions.LOCATION);
    if (status !== "granted") {
      this.setState({
        errorMessage: "Permission to access location was denied"
      });
    }

    const options = {
      accuracy: Location.Accuracy.High,
      timeInterval: 1000 * 5,
      distanceInterval: 5,
      showsBackgroundLocationIndicator: true
    };
    Location.startLocationUpdatesAsync(MY_LOCATION_TASK, options).then(
      locations => {
        // console.debug("locations", JSON.stringify(locations));
      },
      error => {
        alert("startLocationUpdatesAsync failed");
        console.error("locations", error);
      }
    );
  }

  render() {
    return (
      <View style={styles.container}>
        <Button title="Track Me" onPress={() => this.startTracking()} />
      </View>
    );
  }
}

TaskManager.defineTask(MY_LOCATION_TASK, ({ data: { locations }, error }) => {
  if (error) {
    // check `error.message` for more details.
    console.error("Location task error", error);
    return;
  }
  //console.log("Received new locations", JSON.stringify(locations));
  let { coords } = locations[0];
  console.log("location detected", coords.longitude + " " + coords.longitude);

  //send data to firebase
});

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#fff",
    alignItems: "center",
    justifyContent: "center"
  }
});