Expo DeviceMotion

一个提供设备运动和方向传感器访问权限的库

Android

iOS

Web

Included in Expo Go

GitHub

npm

更新日志

Recommended version:

~58.0.0

expo-sensors 中的 DeviceMotion 提供对设备运动和方向传感器的访问。所有数据均以穿过设备的三个轴为基准。以纵向为准：X 轴从左向右，Y 轴从底部向顶部，Z 轴垂直穿过屏幕，从背面指向正面。

安装

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.

在应用配置中配置

如果项目使用配置插件（持续原生生成（CNG）），则可以使用内置的配置插件来配置来自 expo-sensor 的 DeviceMotion。该插件允许配置各种无法在运行时设置、且必须重新构建应用二进制文件才能生效的属性。如果应用不使用 CNG，则需要手动配置该库。

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 用于设置 `NSMotionUsageDescription` 权限提示的字符串。

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

如果未使用持续原生生成（CNG），或者手动使用原生 ios 项目，则需要在原生项目中配置 NSMotionUsageDescription 键，才能访问 DeviceMotion 数据：

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.

权限

iOS

此库使用以下使用说明键：

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