Expo DeviceMotion

A library that provides access to a device's motion and orientation sensors.

Android

iOS

Web

Included in Expo Go

GitHub

npm

Changelog

Recommended version:

~55.0.19

DeviceMotion from expo-sensors provides access to the device motion and orientation sensors. All data is presented in terms of three axes that run through a device. According to portrait orientation: X runs from left to right, Y from bottom to top and Z perpendicularly through the screen from back to front.

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.

Configuration in app config

You can configure DeviceMotion from expo-sensor using its built-in config plugin if you use config plugins in your project (Continuous Native Generation (CNG)). The plugin allows you to configure various properties that cannot be set at runtime and require building a new app binary to take effect. If your app does not use CNG, then you'll need to manually configure the library.

Example app.json with config plugin

app.json

{
  "expo": {
    "plugins": [
      [
        "expo-sensors",
        {
          "motionPermission": "Allow $(PRODUCT_NAME) to access your device motion."
        }
      ]
    ]
  }
}

Configurable properties

Name	Default	Description
`motionPermission`	`"Allow $(PRODUCT_NAME) to access your device motion"`	Only for: iOS A string to set the `NSMotionUsageDescription` permission message.

Are you using this library in an existing React Native app?

If you're not using Continuous Native Generation (CNG) or you're using native ios project manually, then you need to configure NSMotionUsageDescription key in your native project to access DeviceMotion stats:

ios/[app]/Info.plist

<key>NSMotionUsageDescription</key>
<string>Allow $(PRODUCT_NAME) to access your device motion</string>

API

import { DeviceMotion } from 'expo-sensors';

Constants

`Gravity`

Android

iOS

Web

Type: number

Constant value representing standard gravitational acceleration for Earth (9.80665 m/s^2).

Classes

`DeviceMotion`

Android

iOS

Web

Type: Class extends DeviceSensor<DeviceMotionMeasurement>

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

DeviceMotion Properties

`Gravity`

Android

iOS

Web

Type: number • Default: ExponentDeviceMotion.Gravity

Constant value representing standard gravitational acceleration for Earth (9.80665 m/s^2).

DeviceMotion Methods

`addListener(listener)`

Android

iOS

Web

Parameter	Type	Description
listener	`Listener<DeviceMotionMeasurement>`	A callback that is invoked when a device motion sensor update is available. When invoked, the listener is provided a single argument that is a `DeviceMotionMeasurement` object.

Subscribe for updates to the device motion sensor.

Returns:

EventSubscription

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

`getListenerCount()`

Android

iOS

Web

Returns the registered listeners count.

Returns:

number

`getPermissionsAsync()`

Android

iOS

Web

Checks user's permissions for accessing sensor.

Returns:

Promise<PermissionResponse>

`hasListeners()`

Android

iOS

Web

Returns boolean which signifies if sensor has any listeners registered.

Returns:

boolean

`isAvailableAsync()`

Android

iOS

Web

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 DeviceMotion.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.

Returns:

Promise<boolean>

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

`removeAllListeners()`

Android

iOS

Web

Removes all registered listeners.

Returns:

void

Deprecated: use subscription.remove() instead.

`removeSubscription(subscription)`

Android

iOS

Web

Parameter	Type
subscription	`EventSubscription`

Returns:

void

`requestPermissionsAsync()`

Android

iOS

Web

Asks the user to grant permissions for accessing sensor.

Returns:

Promise<PermissionResponse>

`setUpdateInterval(intervalMs)`

Android

iOS

Web

Parameter	Type	Description
intervalMs	`number`	Desired interval in milliseconds between sensor updates. Starting from Android 12 (API level 31), the system has a 200Hz limit for each sensor updates. If you need an update interval of greater than 200Hz, you should add `android.permission.HIGH_SAMPLING_RATE_SENSORS` to app.json `permissions` field or if you are using an existing React Native project, add `<uses-permission android:name="android.permission.HIGH_SAMPLING_RATE_SENSORS"/>` to AndroidManifest.xml.

Set the sensor update interval.

Returns:

void

Interfaces

`Subscription`

Android

iOS

Web

A subscription object that allows to conveniently remove an event listener from the emitter.

Subscription Methods

`remove()`

Android

iOS

Web

Removes an event listener for which the subscription has been created. After calling this function, the listener will no longer receive any events from the emitter.

Returns:

void

Types

`DeviceMotionMeasurement`

Android

iOS

Web

Property	Type	Description
acceleration	`null \| { timestamp: number, x: number, y: number, z: number }`	Device acceleration on the three axis as an object with `x`, `y`, `z` keys. Expressed in meters per second squared (m/s^2).
accelerationIncludingGravity	`{ timestamp: number, x: number, y: number, z: number }`	Device acceleration with the effect of gravity on the three axis as an object with `x`, `y`, `z` keys. Expressed in meters per second squared (m/s^2).
interval	`number`	Interval at which data is obtained from the native platform. Expressed in milliseconds (ms).
orientation	`DeviceMotionOrientation`	Device orientation based on screen rotation. Value is one of: `0` (portrait), `90` (right landscape), `180` (upside down), `-90` (left landscape).
rotation	`{ alpha: number, beta: number, gamma: number, timestamp: number }`	Device's orientation in space as an object with alpha, beta, gamma keys where alpha is for rotation around Z axis, beta for X axis rotation and gamma for Y axis rotation.
rotationRate	`null \| { alpha: number, beta: number, gamma: number, timestamp: number }`	Device's rate of rotation in space expressed in degrees per second (deg/s).

`PermissionExpiration`

Android

iOS

Web

Literal type: union

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

Acceptable values are: 'never' | number

`PermissionResponse`

Android

iOS

Web

An object obtained by permissions get and request functions.

Property	Type	Description
canAskAgain	`boolean`	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.
expires	`PermissionExpiration`	Determines time when the permission expires.
granted	`boolean`	A convenience boolean that indicates if the permission is granted.
status	`PermissionStatus`	Determines the status of the permission.

Enums

`DeviceMotionOrientation`

Android

iOS

Web

`LeftLandscape`

DeviceMotionOrientation.LeftLandscape ＝ -90

`Portrait`

DeviceMotionOrientation.Portrait ＝ 0

`RightLandscape`

DeviceMotionOrientation.RightLandscape ＝ 90

`UpsideDown`

DeviceMotionOrientation.UpsideDown ＝ 180

`PermissionStatus`

Android

iOS

Web

`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.

Permissions

iOS

The following usage description keys are used by this library:

Info.plist key	Description
`NSMotionUsageDescription`	A message that tells the user why the app is requesting access to the device’s motion data.