Source: https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion

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Expo DeviceMotion

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

GitHub Changelog npm

Android

iOS

Web

Bundled version:

~14.1.4

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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

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Terminal

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- npx 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

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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

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{ "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: <br><br>iOS<br><br> <br><br>A string to set the NSMotionUsageDescription<br> 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

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

API

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import { DeviceMotion } from 'expo-sensors';

Constants

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Gravity

Type: number

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

Classes

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DeviceMotion

Type: Class extends [DeviceSensor](https://docs.expo.dev/versions/latest/sdk/sensors) <[DeviceMotionMeasurement](https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion#devicemotionmeasurement) >

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

DeviceMotion Properties

Gravity

Type: number • Default: ExponentDeviceMotion.Gravity

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

DeviceMotion Methods

addListener(listener)

| Parameter | Type | Description | | --- | --- | --- | | listener | Listener<[DeviceMotionMeasurement](https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion#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()

Returns the registered listeners count.

Returns:

number

getPermissionsAsync()

Checks user's permissions for accessing sensor.

Returns:

[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) <PermissionResponse>

hasListeners()

Returns boolean which signifies if sensor has any listeners registered.

Returns:

boolean

isAvailableAsync()

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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) <boolean>

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

removeAllListeners()

Removes all registered listeners.

Returns:

void

removeSubscription(subscription)

| Parameter | Type | Description | | --- | --- | --- | | subscription | EventSubscription | A subscription to remove. |

Removes the given subscription.

Returns:

void

requestPermissionsAsync()

Asks the user to grant permissions for accessing sensor.

Returns:

[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) <PermissionResponse>

setUpdateInterval(intervalMs)

| Parameter | Type | Description | | --- | --- | --- | | intervalMs | number | Desired interval in milliseconds between sensor updates.<br><br>> Starting from Android 12 (API level 31), the system has a 200ms limit for each sensor updates.<br>> <br>> If you need an update interval less than 200ms, you should:<br>> <br>> * add android.permission.HIGH_SAMPLING_RATE_SENSORS to app.json permissions field<br>> <br>> * 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.

Returns:

void

Interfaces

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Subscription

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

Subscription Methods

remove()

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

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DeviceMotionMeasurement

| 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](https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion#devicemotionorientation) | Device orientation based on screen rotation. Value is one of:<br><br>* 0 (portrait),<br>* 90 (right landscape),<br>* 180 (upside down),<br>* -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

Literal Type: union

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

Acceptable values are: 'never' | number

PermissionResponse

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](https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion#permissionexpiration) | Determines time when the permission expires. | | granted | boolean | A convenience boolean that indicates if the permission is granted. | | status | [PermissionStatus](https://docs.expo.dev/versions/v53.0.0/sdk/devicemotion#permissionstatus) | Determines the status of the permission. |

Enums

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DeviceMotionOrientation

LeftLandscape

DeviceMotionOrientation.LeftLandscape ＝ -90

Portrait

DeviceMotionOrientation.Portrait ＝ 0

RightLandscape

DeviceMotionOrientation.RightLandscape ＝ 90

UpsideDown

DeviceMotionOrientation.UpsideDown ＝ 180

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.

Permissions

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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. |