A library that provides access to the device's accelerometer sensor.
Accelerometer
from expo-sensors
provides access to the device accelerometer sensor(s) and associated listeners to respond to changes in acceleration in three-dimensional space, meaning any movement or vibration.
-
npx expo install expo-sensors
If you are installing this in an existing React Native app, start by installing expo
in your project. Then, follow the additional instructions as mentioned by the library's README under "Installation in bare React Native projects" section.
import { useState, useEffect } from 'react';
import { StyleSheet, Text, TouchableOpacity, View } from 'react-native';
import { Accelerometer } from 'expo-sensors';
export default function App() {
const [{ x, y, z }, setData] = useState({
x: 0,
y: 0,
z: 0,
});
const [subscription, setSubscription] = useState(null);
const _slow = () => Accelerometer.setUpdateInterval(1000);
const _fast = () => Accelerometer.setUpdateInterval(16);
const _subscribe = () => {
setSubscription(Accelerometer.addListener(setData));
};
const _unsubscribe = () => {
subscription && subscription.remove();
setSubscription(null);
};
useEffect(() => {
_subscribe();
return () => _unsubscribe();
}, []);
return (
<View style={styles.container}>
<Text style={styles.text}>Accelerometer: (in gs where 1g = 9.81 m/s^2)</Text>
<Text style={styles.text}>x: {x}</Text>
<Text style={styles.text}>y: {y}</Text>
<Text style={styles.text}>z: {z}</Text>
<View style={styles.buttonContainer}>
<TouchableOpacity onPress={subscription ? _unsubscribe : _subscribe} style={styles.button}>
<Text>{subscription ? 'On' : 'Off'}</Text>
</TouchableOpacity>
<TouchableOpacity onPress={_slow} style={[styles.button, styles.middleButton]}>
<Text>Slow</Text>
</TouchableOpacity>
<TouchableOpacity onPress={_fast} style={styles.button}>
<Text>Fast</Text>
</TouchableOpacity>
</View>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
paddingHorizontal: 20,
},
text: {
textAlign: 'center',
},
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',
},
});
import { Accelerometer } from 'expo-sensors';
Accelerometer
Type: Class extends DeviceSensor<AccelerometerMeasurement>
A base class for subscribable sensors. The events emitted by this class are measurements
specified by the parameter type Measurement
.
Accelerometer Methods
addListener(listener)
Parameter | Type | Description |
---|---|---|
listener | Listener<AccelerometerMeasurement> | A callback that is invoked when an accelerometer update is available. When invoked,
the listener is provided a single argument that is an |
Subscribe for updates to the accelerometer.
A subscription that you can call remove()
on when you would like to unsubscribe the listener.
hasListeners()
Returns boolean which signifies if sensor has any listeners registered.
boolean
isAvailableAsync()
You should always check the sensor availability before attempting to use it.
Returns whether the accelerometer is enabled on the device.
On mobile web, you must first invoke Accelerometer.requestPermissionsAsync()
in a user interaction (i.e. touch event) before you can use this module.
If the status
is not equal to granted
then you should inform the end user that they may have to open settings.
On web this starts a timer and waits to see if an event is fired. This should predict if the iOS device has the device orientation API disabled in
Settings > Safari > Motion & Orientation Access. Some devices will also not fire if the site isn't hosted with HTTPS as DeviceMotion
is now considered a secure API.
There is no formal API for detecting the status of DeviceMotion
so this API can sometimes be unreliable on web.
Promise<boolean>
A promise that resolves to a boolean
denoting the availability of the accelerometer.
removeSubscription(subscription)
Parameter | Type | Description |
---|---|---|
subscription | Subscription | A subscription to remove. |
Removes the given subscription.
void
setUpdateInterval(intervalMs)
Parameter | 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. |
AccelerometerMeasurement
Each of these keys represents the acceleration along that particular axis in g-force (measured in g
s).
A g
is a unit of gravitational force equal to that exerted by the earth’s gravitational field (9.81 m/s^2
).
Name | Type | Description |
---|---|---|
timestamp | number | Timestamp of the measurement in seconds. |
x | number | Value of |
y | number | Value of |
z | number | Value of |
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.