App.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React, { Component } from 'react';
import { Platform, StyleSheet, Text, View, Button } from 'react-native';
import { NativeModules, NativeEventEmitter } from 'react-native';

const { Captuvo, CaptuvoEventEmitter } = NativeModules;
const eventEmitter = new NativeEventEmitter(CaptuvoEventEmitter);

const instructions = Platform.select({
  ios: 'Press Cmd+R fdgdfgto reload,\n' + 'Cmd+D or shake for dev menu',
  android:
    'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});


type Props = {};
export default class App extends Component<Props> {
  constructor(props) {
    super(props);
    this.onBarCodeScan = this.onBarCodeScan.bind(this);
    this.state = { barcode: "----" };
  }
  launch = () => {
    Captuvo.startDecoderHardware();
    /* const subscription =  */eventEmitter.addListener('onBarCodeScan', this.onBarCodeScan);
    eventEmitter.addListener('onDecoderReady', this.justLog);
  }
  scan = () => {
    Captuvo.scan();
  }
  onBarCodeScan = e => {
    this.setState({ barcode: e.data });
  }
  justLog = e => {
    console.log(e)
  }
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>Welcome to React Native!</Text>
        <Text style={styles.instructions}>barcode: {this.state.barcode}</Text>
        <Button
          onPress={this.launch}
          title="Launch scanner"
          color="#FF6347" />
        <Button
          onPress={this.scan}
          title="Scan"
          color="#FF6347" />
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});