Expo

Documentation

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Gyroscope

Access the device gyroscope sensor to respond to changes in rotation in 3d space.

Expo.Gyroscope.addListener(listener)

Subscribe for updates to the gyroscope.

Arguments

  • listener (function) -- A callback that is invoked when an gyroscope update is available. When invoked, the listener is provided a single argumument that is an object containing keys x, y, z.

Returns

An EventSubscription object that you can call remove() on when you would like to unsubscribe the listener.

Expo.Gyroscope.removeAllListeners()

Remove all listeners.

Expo.Gyroscope.setUpdateInterval(intervalMs)

Subscribe for updates to the gyroscope.

Arguments

  • intervalMs (number) -- Desired interval in milliseconds between gyroscope updates.

Example: basic subscription

import React from 'react';
import {
  Gyroscope,
} from 'expo';
import {
  StyleSheet,
  Text,
  TouchableOpacity,
  View
} from 'react-native';

export default class GyroscopeSensor extends React.Component {
  state = {
    gyroscopeData: {},
  }

  componentDidMount() {
    this._toggle();
  }

  componentWillUnmount() {
    this._unsubscribe();
  }

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

  _slow = () => {
    Gyroscope.setUpdateInterval(1000);
  }

  _fast = () => {
    Gyroscope.setUpdateInterval(16);
  }

  _subscribe = () => {
    this._subscription = Gyroscope.addListener((result) => {
      this.setState({gyroscopeData: result});
    });
  }

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

  render() {
    let { x, y, z } = this.state.gyroscopeData;

    return (
      <View style={styles.sensor}>
        <Text>Gyroscope:</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,
  },
});