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Expo LightSensor iconExpo LightSensor

GitHub

npm

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

Android

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

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 Light Sensor usage
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,
  },
});

API

import { LightSensor } from 'expo-sensors';

Classes

Only for:
Android

LightSensor

Type: Class extends default<LightSensorMeasurement>

LightSensor Methods

getListenerCount()

Returns the registered listeners count.

Returns:

number

getPermissionsAsync()

Checks user's permissions for accessing sensor.

hasListeners()

Returns boolean which signifies if sensor has any listeners registered.

Returns:

boolean

removeAllListeners()

Removes all registered listeners.

Returns:

void

removeSubscription(subscription)

NameTypeDescription
subscriptionSubscription

A subscription to remove.


Removes the given subscription.

Returns:

void

requestPermissionsAsync()

Asks the user to grant permissions for accessing sensor.

setUpdateInterval(intervalMs)

NameTypeDescription
intervalMsnumber

Desired interval in milliseconds between sensor updates.

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.

Returns:

void

Interfaces

PermissionResponse

An object obtained by permissions get and request functions.

PermissionResponse Properties

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

LightSensorMeasurement

NameTypeDescription
illuminancenumber

Ambient light level registered by the device measured in lux (lx).

timestampnumber

Timestamp of the measurement in seconds.

PermissionExpiration

Literal Type: multiple types

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

Acceptable values are: 'never' | number

Subscription

NameTypeDescription
remove() => void

A method to unsubscribe the listener.

Enums

PermissionStatus

PermissionStatus Values

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.