Source: https://docs.expo.dev/versions/v54.0.0/sdk/light-sensor

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Expo LightSensor

GitHub Changelog npm

A library that provides access to the device's light sensor.

GitHub Changelog npm

Android

Bundled version:

~15.0.7

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LightSensor from expo-sensors provides access to the device's light sensor to respond to illuminance changes.

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.

Usage

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Basic Light Sensor usage

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Open in Snack

import { useState, useEffect } from 'react'; import { StyleSheet, Text, TouchableOpacity, View, Platform } from 'react-native'; import { LightSensor } from 'expo-sensors'; export default function App() { const [{ illuminance }, setData] = useState({ illuminance: 0 }); const [subscription, setSubscription] = useState(null); const toggle = () => { if (subscription) { unsubscribe(); } else { subscribe(); } }; const subscribe = () => { setSubscription( LightSensor.addListener(sensorData => { setData(sensorData); }) ); }; const unsubscribe = () => { subscription && subscription.remove(); setSubscription(null); }; useEffect(() => { subscribe(); return () => unsubscribe(); }, []); return ( <View style={styles.sensor}> <Text>Light Sensor:</Text> <Text> Illuminance: {Platform.OS === 'android' ? `${illuminance} lx` : `Only available on Android`} </Text> <View style={styles.buttonContainer}> <TouchableOpacity onPress={toggle} style={styles.button}> <Text>Toggle</Text> </TouchableOpacity> </View> </View> ); } const styles = StyleSheet.create({ sensor: { flex: 1, justifyContent: 'center', alignItems: 'center', paddingHorizontal: 10, }, buttonContainer: { flexDirection: 'row', alignItems: 'stretch', marginTop: 15, }, button: { flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#eee', padding: 10, }, });

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API

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import { LightSensor } from 'expo-sensors';

Classes

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LightSensor

Only for: 

Android

Type: Class extends [DeviceSensor](https://docs.expo.dev/versions/latest/sdk/sensors) <[LightSensorMeasurement](https://docs.expo.dev/versions/v54.0.0/sdk/light-sensor#lightsensormeasurement) >

LightSensor Methods

addListener(listener)

| Parameter | Type | Description | | --- | --- | --- | | listener | Listener<[LightSensorMeasurement](https://docs.expo.dev/versions/v54.0.0/sdk/light-sensor#lightsensormeasurement) > | A callback that is invoked when a LightSensor update is available. When invoked, the listener is provided a single argument that is the illuminance value. |

Subscribe for updates to the light 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 light sensor is available and enabled on the device. Requires at least Android 2.3 (API Level 9).

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 the light 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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LightSensorMeasurement

| Property | Type | Description | | --- | --- | --- | | illuminance | number | Ambient light level registered by the device measured in lux (lx). | | timestamp | number | Timestamp of the measurement in seconds. |

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/v54.0.0/sdk/light-sensor#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/v54.0.0/sdk/light-sensor#permissionstatus) | Determines the status of the permission. |

Enums

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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.