Expo

Documentation

Accelerometer

Accelerometer from expo-sensors provides access to the device accelerometer sensor(s) and associated listeners to respond to changes in acceleration in 3d space, meaning any movement or vibration.

Platform Compatibility

Android DeviceAndroid EmulatoriOS DeviceiOS SimulatorWeb
✅✅✅❌✅

Installation

expo install expo-sensors

To use this in a bare React Native app, follow the installation instructions.

Example Usage

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

export default function App() {
  const [data, setData] = useState({});

  useEffect(() => {
    _toggle();
  }, []);

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

  const _toggle = () => {
    if (this._subscription) {
      _unsubscribe();
    } else {
      _subscribe();
    }
  };

  const _slow = () => {
    Accelerometer.setUpdateInterval(1000);
  };

  const _fast = () => {
    Accelerometer.setUpdateInterval(16);
  };

  const _subscribe = () => {
    this._subscription = Accelerometer.addListener(accelerometerData => {
      setData(accelerometerData);
    });
  };

  const _unsubscribe = () => {
    this._subscription && this._subscription.remove();
    this._subscription = null;
  };

  let { x, y, z } = data;
  return (
    <View style={styles.sensor}>
      <Text style={styles.text}>Accelerometer: (in Gs where 1 G = 9.81 m s^-2)</Text>
      <Text style={styles.text}>
        x: {round(x)} y: {round(y)} z: {round(z)}
      </Text>
      <View style={styles.buttonContainer}>
        <TouchableOpacity onPress={_toggle} style={styles.button}>
          <Text>Toggle</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>
  );
}

function round(n) {
  if (!n) {
    return 0;
  }

  return Math.floor(n * 100) / 100;
}

API

import { Accelerometer } from 'expo-sensors';

Methods

Accelerometer.isAvailableAsync()

You should always check the sensor availability before attempting to use it.
Returns whether the accelerometer is enabled on the device.
On web this starts a timer and waits to see if an event is fired. This should predict if the iOS device has the device orientation API disabled in Settings > Safari > Motion & Orientation Access. Some devices will also not fire if the site isn't hosted with HTTPS as DeviceMotion is now considered a secure API. There is no formal API for detecting the status of DeviceMotion so this API can sometimes be unreliable on web.

Returns

  • A promise that resolves to a boolean denoting the availability of the sensor.

Accelerometer.addListener(listener)

Subscribe for updates to the accelerometer.

Arguments

  • listener (function) -- A callback that is invoked when an accelerometer update is available. When invoked, the listener is provided a single argument that is an object containing keys x, y, z. Each of these keys represents the acceleration along that particular axis in Gs (A G is a unit of gravitational force equal to that exerted by the earth’s gravitational field (9.81 m s-2).

Returns

  • A subscription that you can call remove() on when you would like to unsubscribe the listener.

Accelerometer.removeAllListeners()

Remove all listeners.

Accelerometer.setUpdateInterval(intervalMs)

Subscribe for updates to the accelerometer.

Arguments

  • intervalMs (number) Desired interval in milliseconds between accelerometer updates.