This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 57).

Expo Magnetometer

A library that provides access to the device's magnetometer sensor.

Android

iOS

Included in Expo Go

Magnetometer from expo-sensors provides access to the device magnetometer sensor(s) to respond to and measure the changes in the magnetic field measured in microtesla (μT).

You can access the calibrated values with Magnetometer and uncalibrated raw values with MagnetometerUncalibrated.

Installation

Terminal

- npx expo install expo-sensors

- yarn expo install expo-sensors

- pnpm expo install expo-sensors

- bun expo install expo-sensors

If you are installing this in an existing React Native app, make sure to install expo in your project.

Usage

Magnetometer

import { useState, useEffect } from 'react';
import { StyleSheet, Text, TouchableOpacity, View } from 'react-native';
import { Magnetometer } from 'expo-sensors';

export default function Compass() {
  const [{ x, y, z }, setData] = useState({
    x: 0,
    y: 0,
    z: 0,
  });
  const [subscription, setSubscription] = useState(null);

  const _slow = () => Magnetometer.setUpdateInterval(1000);
  const _fast = () => Magnetometer.setUpdateInterval(16);

  const _subscribe = () => {
    setSubscription(
      Magnetometer.addListener(result => {
        setData(result);
      })
    );
  };

  const _unsubscribe = () => {
    subscription && subscription.remove();
    setSubscription(null);
  };

  useEffect(() => {
    _subscribe();
    return () => _unsubscribe();
  }, []);

  return (
    <View style={styles.container}>
      <Text style={styles.text}>Magnetometer:</Text>
      <Text style={styles.text}>x: {x}</Text>
      <Text style={styles.text}>y: {y}</Text>
      <Text style={styles.text}>z: {z}</Text>
      <View style={styles.buttonContainer}>
        <TouchableOpacity onPress={subscription ? _unsubscribe : _subscribe} style={styles.button}>
          <Text>{subscription ? 'On' : 'Off'}</Text>
        </TouchableOpacity>
        <TouchableOpacity onPress={_slow} style={[styles.button, styles.middleButton]}>
          <Text>Slow</Text>
        </TouchableOpacity>
        <TouchableOpacity onPress={_fast} style={styles.button}>
          <Text>Fast</Text>
        </TouchableOpacity>
      </View>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    paddingHorizontal: 10,
  },
  text: {
    textAlign: 'center',
  },
  buttonContainer: {
    flexDirection: 'row',
    alignItems: 'stretch',
    marginTop: 15,
  },
  button: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#eee',
    padding: 10,
  },
  middleButton: {
    borderLeftWidth: 1,
    borderRightWidth: 1,
    borderColor: '#ccc',
  },
});

API

import { Magnetometer, MagnetometerUncalibrated } from 'expo-sensors';

No API data file found, sorry!