App.js

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
import Camera from 'react-native-camera';

export default class App extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Camera
          ref={(cam) =>{ this.camera = cam}}
          style={styles.view}
          aspect={Camera.constraint.Aspect.fill}>
          <Text
          style={styles.capture}
          onPress={this.takePicture.bind(this)}>
          [CAPTURE_IMAGE] </Text>
          </Camera>
      </View>
    );
  }
  takePicture(){
    const options = {}
    this.camera.capture({metadata: options}).then((data)=>{
      console.log(data)
    }).catch((error)=>{
      console.log(error)
    })
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    flexDirection: 'row'
  },
  view: {
    flex: 1,
    justifyContent: 'flex-end',
    alignItems: 'center'
  },
  capture: {
    flex: 0,
    backgroundColor: 'steelblue',
    borderRadius: 10,
    color: 'red',
    padding: 15,
    margin: 45
  }
});