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Expo Application Services
API Reference

Accelerometer


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

Platform Compatibility

Android DeviceAndroid EmulatoriOS DeviceiOS SimulatorWeb
Status-success-iconStatus-success-iconStatus-success-iconStatus-failed-iconStatus-success-icon

Installation

Terminal
npx expo install expo-sensors

If you're installing this in a bare React Native app, you should also follow these additional installation instructions.

Usage

Basic Accelerometer 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 [{ x, y, z }, setData] = useState({
    x: 0,
    y: 0,
    z: 0,
  });
  const [subscription, setSubscription] = useState(null);

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

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

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

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

  return (
    <View style={styles.container}>
      <Text style={styles.text}>Accelerometer: (in gs where 1g = 9.81 m/s^2)</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>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    paddingHorizontal: 20,
  },
  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 { Accelerometer } from 'expo-sensors';

Classes

Accelerometer

Type: Class extends DeviceSensor<AccelerometerMeasurement>

A base class for subscribable sensors. The events emitted by this class are measurements specified by the parameter type M.

addListener(listener)

NameTypeDescription
listenerListener<AccelerometerMeasurement>

A callback that is invoked when an accelerometer update is available. When invoked, the listener is provided a single argument that is an AccelerometerMeasurement object.


Subscribe for updates to the accelerometer.

  • Undo-iconSubscription

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

getListenerCount()

Returns the registered listeners count.

  • Undo-iconnumber

getPermissionsAsync()

Checks user's permissions for accessing sensor.


hasListeners()

Returns boolean which signifies if sensor has any listeners registered.

  • Undo-iconboolean

isAvailableAsync()

Info-icon
You should always check the sensor availability before attempting to use it.

Returns whether the accelerometer is enabled on the device.

On mobile web, you must first invoke Accelerometer.requestPermissionsAsync() in a user interaction (i.e. touch event) before you can use this module. If the status is not equal to granted then you should inform the end user that they may have to open settings.

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.


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

removeAllListeners()

Removes all registered listeners.

  • Undo-iconvoid

removeSubscription(subscription)

NameTypeDescription
subscriptionSubscription

A subscription to remove.


Removes the given subscription.

  • Undo-iconvoid

requestPermissionsAsync()

Asks the user to grant permissions for accessing sensor.


setUpdateInterval(intervalMs)

NameTypeDescription
intervalMsnumber

Desired interval in milliseconds between sensor updates.

Info-icon

Starting from Android 12 (API level 31), the system has a 200ms limit for each sensor updates.

If you need an update interval less than 200ms, you should:

  • add android.permission.HIGH_SAMPLING_RATE_SENSORS to app.json permissions field
  • or if you are using bare workflow, add <uses-permission android:name="android.permission.HIGH_SAMPLING_RATE_SENSORS"/> to AndroidManifest.xml.

Set the sensor update interval.

  • Undo-iconvoid

Interfaces

PermissionResponse

An object obtained by permissions get and request functions.

NameTypeDescription
canAskAgainboolean

Indicates if user can be asked again for specific permission. If not, one should be directed to the Settings app in order to enable/disable the permission.

expiresPermissionExpiration

Determines time when the permission expires.

grantedboolean

A convenience boolean that indicates if the permission is granted.

statusPermissionStatus

Determines the status of the permission.


Types

AccelerometerMeasurement

Each of these keys represents the acceleration along that particular axis in g-force (measured 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).

NameTypeDescription
xnumber

Value of gs device reported in X axis.

ynumber

Value of gs device reported in Y axis.

znumber

Value of gs device reported in Z axis.

PermissionExpiration

Permission expiration time. Currently, all permissions are granted permanently.

Acceptable values are: 'never', number.

Subscription

NameTypeDescription
remove() => void-

Enums

PermissionStatus

DENIED

PermissionStatus.DENIED = "denied"

User has denied the permission.

GRANTED

PermissionStatus.GRANTED = "granted"

User has granted the permission.

UNDETERMINED

PermissionStatus.UNDETERMINED = "undetermined"

User hasn't granted or denied the permission yet.

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