A library that provides access to the device's light sensor.
GitHub
npm
LightSensor
from expo-sensors
provides access to the device's light sensor to respond to illuminance changes.
-
npx expo install expo-sensors
If you are installing this in an existing React Native app (bare workflow), start by installing expo
in your project. Then, follow the additional instructions as mentioned by library's README under "Installation in bare React Native projects" section.
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,
},
});
import { LightSensor } from 'expo-sensors';
LightSensor
Type: Class extends default<LightSensorMeasurement>
LightSensor Methods
hasListeners()
Returns boolean which signifies if sensor has any listeners registered.
boolean
removeSubscription(subscription)
Name | Type | Description |
---|---|---|
subscription | Subscription | A subscription to remove. |
Removes the given subscription.
void
setUpdateInterval(intervalMs)
Name | Type | Description |
---|---|---|
intervalMs | number | Desired interval in milliseconds between sensor updates.
|
Set the sensor update interval.
void
PermissionResponse
An object obtained by permissions get and request functions.
PermissionResponse Properties
Name | 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. |
LightSensorMeasurement
Name | 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: multiple types
Permission expiration time. Currently, all permissions are granted permanently.
Acceptable values are: 'never'
| number
Subscription
Name | Type | Description |
---|---|---|
remove | () => void | A method to unsubscribe the listener. |
PermissionStatus
PermissionStatus Values
UNDETERMINED
PermissionStatus.UNDETERMINED = "undetermined"
User hasn't granted or denied the permission yet.