Source: https://docs.expo.dev/versions/v54.0.0/sdk/barometer

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Expo Barometer

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A library that provides access to device's barometer sensor.

GitHub Changelog npm

Android

iOS (device only)

Bundled version:

~15.0.7

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Barometer from expo-sensors provides access to the device barometer sensor to respond to changes in air pressure, which is measured in hectopascals (hPa).

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 Barometer usage

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Open in Snack

import { useState } from 'react'; import { StyleSheet, Text, TouchableOpacity, View, Platform } from 'react-native'; import { Barometer } from 'expo-sensors'; export default function App() { const [{ pressure, relativeAltitude }, setData] = useState({ pressure: 0, relativeAltitude: 0 }); const [subscription, setSubscription] = useState(null); const toggleListener = () => { subscription ? unsubscribe() : subscribe(); }; const subscribe = () => { setSubscription(Barometer.addListener(setData)); }; const unsubscribe = () => { subscription && subscription.remove(); setSubscription(null); }; return ( <View style={styles.wrapper}> <Text>Barometer: Listener {subscription ? 'ACTIVE' : 'INACTIVE'}</Text> <Text>Pressure: {pressure} hPa</Text> <Text> Relative Altitude:{' '} {Platform.OS === 'ios' ? `${relativeAltitude} m` : `Only available on iOS`} </Text> <TouchableOpacity onPress={toggleListener} style={styles.button}> <Text>Toggle listener</Text> </TouchableOpacity> </View> ); } const styles = StyleSheet.create({ button: { justifyContent: 'center', alignItems: 'center', backgroundColor: '#eee', padding: 10, marginTop: 15, }, wrapper: { flex: 1, alignItems: 'stretch', justifyContent: 'center', paddingHorizontal: 20, }, });

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API

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import { Barometer } from 'expo-sensors';

Classes

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Barometer

Only for: 

Android

iOS

Type: Class extends [DeviceSensor](https://docs.expo.dev/versions/latest/sdk/sensors) <[BarometerMeasurement](https://docs.expo.dev/versions/v54.0.0/sdk/barometer#barometermeasurement) >

Barometer Methods

addListener(listener)

| Parameter | Type | Description | | --- | --- | --- | | listener | Listener<[BarometerMeasurement](https://docs.expo.dev/versions/v54.0.0/sdk/barometer#barometermeasurement) > | A callback that is invoked when a barometer update is available. When invoked, the listener is provided with a single argument that is BarometerMeasurement. |

Subscribe for updates to the barometer.

Returns:

EventSubscription

A subscription that you can call remove() on when you would like to unsubscribe the listener.

Example

const subscription = Barometer.addListener(({ pressure, relativeAltitude }) => { console.log({ pressure, relativeAltitude }); });

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.

Check the availability of the device barometer. Requires at least Android 2.3 (API Level 9) and iOS 8.

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 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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BarometerMeasurement

The altitude data returned from the native sensors.

| Property | Type | Description | | --- | --- | --- | | pressure | number | Measurement in hectopascals (hPa). | | relativeAltitude(optional) | number | Only for: <br><br>iOS<br><br> <br><br>Measurement in meters (m). | | 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/barometer#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/barometer#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.

Units and providers

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| OS | Units | Provider | Description | | --- | --- | --- | --- | | iOS | hPa | CMAltimeter | Altitude events reflect the change in the current altitude, not the absolute altitude. | | Android | hPa | Sensor.TYPE_PRESSURE | Monitoring air pressure changes. | | Web | | | This sensor is not available on the web and cannot be accessed. An UnavailabilityError will be thrown if you attempt to get data. |