App.js.bak

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

export default function App() {
  const [{ illuminance }, setData] = useState({ illuminance: 0 });

  useEffect(() => {
    _toggle();

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

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

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

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

  return (
    <View style={styles.sensor}>
      <Text>Light Sensor:</Text>
      <Text>
        Illuminance: {Platform.OS === 'android' ? `${illuminance} lx` : `Only available on Android`}
      </Text>
      <View style={styles.buttonContainer}>
        <TouchableOpacity onPress={_toggle} style={styles.button}>
          <Text>Toggle</Text>
        </TouchableOpacity>
      </View>
    </View>
  );
}

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,
  },
});