Magnetometer Magnetometer
from expo-sensors
provides access to the device magnetometer sensor(s) to respond to and measure the changes in the magnetic field. You can access the calibrated values with Magnetometer.
and uncalibrated raw values with MagnetometerUncalibrated
.
Platform Compatibility Android Device Android Emulator iOS Device iOS Simulator Web
import { Magnetometer } from 'expo-sensors' ;
You should always check the sensor availability before attempting to use it.
Returns whether the magnetometer is enabled on the device.
OS Availability iOS iOS 8+ Android Android 2.3+ (API Level 9+) Web N/A
A promise that resolves to a boolean
denoting the availability of the sensor. Subscribe for updates to the Magnetometer.
listener (function ) -- A callback that is invoked when an
Magnetometer update is available. When invoked, the listener is
provided a single argumument that is an object containing keys x, y,
z.A subscription that you can call remove()
on when you
would like to unsubscribe the listener. Remove all listeners.
Subscribe for updates to the Magnetometer.
intervalMs (number ) Desired interval in milliseconds between
Magnetometer updates.import React from 'react' ;
import { Magnetometer } from 'expo-sensors' ;
import { StyleSheet , Text , TouchableOpacity , View } from 'react-native' ;
export default class MagnetometerSensor extends React. Component {
state = {
MagnetometerData : { } ,
} ;
componentDidMount ( ) {
this . _toggle ( ) ;
}
componentWillUnmount ( ) {
this . _unsubscribe ( ) ;
}
_toggle = ( ) => {
if ( this . _subscription ) {
this . _unsubscribe ( ) ;
} else {
this . _subscribe ( ) ;
}
} ;
_slow = ( ) => {
Magnetometer . setUpdateInterval ( 1000 ) ;
} ;
_fast = ( ) => {
Magnetometer . setUpdateInterval ( 16 ) ;
} ;
_subscribe = ( ) => {
this . _subscription = Magnetometer . addListener ( result => {
this . setState ( { MagnetometerData : result } ) ;
} ) ;
} ;
_unsubscribe = ( ) => {
this . _subscription && this . _subscription . remove ( ) ;
this . _subscription = null ;
} ;
render ( ) {
let { x, y, z } = this . state . MagnetometerData ;
return (
< View style= { styles. sensor } >
< Text > Magnetometer : < / Text >
< Text >
x: { round ( x) } y: { round ( y) } z: { round ( z) }
< / Text >
< View style= { styles. buttonContainer } >
< TouchableOpacity onPress= { this . _toggle } style= { styles. button } >
< Text > Toggle < / Text >
< / TouchableOpacity >
< TouchableOpacity onPress= { this . _slow } style= { [ styles. button , styles. middleButton ] } >
< Text > Slow < / Text >
< / TouchableOpacity >
< TouchableOpacity onPress= { this . _fast } style= { styles. button } >
< Text > Fast < / Text >
< / TouchableOpacity >
< / View >
< / View >
) ;
}
}
function round ( n ) {
if ( ! n) {
return 0 ;
}
return Math . floor ( n * 100 ) / 100 ;
}
const styles = StyleSheet . create ( {
container: {
flex: 1 ,
} ,
buttonContainer: {
flexDirection: 'row' ,
alignItems: 'stretch' ,
marginTop: 15 ,
} ,
button: {
flex: 1 ,
justifyContent: 'center' ,
alignItems: 'center' ,
backgroundColor: '#eee' ,
padding: 10 ,
} ,
middleButton: {
borderLeftWidth: 1 ,
borderRightWidth: 1 ,
borderColor: '#ccc' ,
} ,
sensor: {
marginTop: 15 ,
paddingHorizontal: 10 ,
} ,
} ) ;