Barometer

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

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web

Installation

expo install expo-sensors

If you're installing this in a bare React Native app, you should also follow these additional installation instructions.

Usage

import React, { useState, useEffect } from 'react';
import { StyleSheet, Text, TouchableOpacity, View, Platform } from 'react-native';
import { Barometer } from 'expo-sensors';

export default function App() {
  const [data, setData] = useState({});

  useEffect(() => {
    _toggle();
  }, []);

  useEffect(() => {
    return () => {
      _unsubscribe();
    };
  }, []);

  const _toggle = () => {
    if (this._subscription) {
      _unsubscribe();
    } else {
      _subscribe();
    }
  };

  const _subscribe = () => {
    this._subscription = Barometer.addListener(barometerData => {
      setData(barometerData);
    });
  };

  const _unsubscribe = () => {
    this._subscription && this._subscription.remove();
    this._subscription = null;
  };

  const { pressure = 0, relativeAltitude = 0 } = data;

  return (
    <View style={styles.sensor}>
      <Text>Barometer:</Text>
      <Text>Pressure: {pressure * 100} Pa</Text>
      <Text>
        Relative Altitude:{' '}
        {Platform.OS === 'ios' ? `${relativeAltitude} m` : `Only available on iOS`}
      </Text>
      <View style={styles.buttonContainer}>
        <TouchableOpacity onPress={_toggle} style={styles.button}>
          <Text>Toggle</Text>
        </TouchableOpacity>
      </View>
    </View>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  buttonContainer: {
    flexDirection: 'row',
    alignItems: 'stretch',
    marginTop: 15,
  },
  button: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#eee',
    padding: 10,
  },
  sensor: {
    marginTop: 45,
    paddingHorizontal: 10,
  },
});

API

import { Barometer } from 'expo-sensors';

Methods

`Barometer.isAvailableAsync()`

You should always check the sensor availability before attempting to use it.

Returns a promise which resolves into a boolean denoting the availability of the device barometer.

OS	Availability
iOS	iOS 8+
Android	Android 2.3+ (API Level 9+)
Web	`N/A`

Returns

A promise that resolves to a boolean denoting the availability of the sensor.

`Barometer.addListener((data: BarometerMeasurement) => void)`

Subscribe for updates to the barometer.

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

Arguments

listener (function) -- A callback that is invoked when an barometer update is available. When invoked, the listener is provided a single argument that is an object containing: pressure: number (hPa). On iOS the relativeAltitude: number (meters) value will also be available.

Returns

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

`Barometer.removeAllListeners()`

Removes all listeners.

Types

`BarometerMeasurement`

The altitude data returned from the native sensors.

type BarometerMeasurement = {
  pressure: number;
  /* iOS Only */
  relativeAltitude?: number;
};

Name	Type	Format	iOS	Android	Web
pressure	`number`	`hPa`	✅	✅	❌
relativeAltitude	`number \| undefined`	`meters`	✅	❌	❌

Units and Providers

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	`N/A`	`N/A`	This sensor is not available on the web and cannot be accessed. An `UnavailabilityError` will be thrown if you attempt to get data.