Expo Docs MCP Server

--- title: Barometer description: A library that provides access to device's barometer sensor. sourceCodeUrl: https://github.com/expo/expo/tree/main/packages/expo-sensors packageName: expo-sensors iconUrl: /static/images/packages/expo-sensors.png platforms: ["android", "ios*"] --- `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 ## Usage ```jsx 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, }, }); ``` ## API ```js ``` ## Units and providers | OS | Units | Provider | Description | | ------- | ---------- | ------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | | iOS | _`hPa`_ | [`CMAltimeter`](https://developer.apple.com/documentation/coremotion/cmaltimeter) | Altitude events reflect the change in the current altitude, not the absolute altitude. | | Android | _`hPa`_ | [`Sensor.TYPE_PRESSURE`](https://developer.android.com/reference/android/hardware/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. |