App.js

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

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

import Camera from 'react-native-openalpr';

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  textContainer: {
    position: 'absolute',
    top: 100,
    left: 50,
  },
  text: {
    textAlign: 'center',
    fontSize: 20,
  },
  preview:{
    flex:1,

  }
});
type Props = {};
export default class App extends Component<Props> {
    constructor(props) {
    super(props);

    this.camera = null;
    this.state = {
      camera: {
        aspect: Camera.constants.Aspect.fill,
      },
      plate: 'Scan a plate',
    };
  }


  onPlateRecognized = ({ plate, confidence }) => {
    if (confidence > 90) {
      this.setState({
        plate,
      })
    }
  }
   render() {
    return (
      <View style={styles.container}>
        <Camera
          ref={(cam) => {
            this.camera = cam;
          }}
          style={styles.preview}
          aspect={this.state.camera.aspect}
          captureQuality={Camera.constants.CaptureQuality.medium}
          country="us"
          onPlateRecognized={this.onPlateRecognized}
          plateOutlineColor="#ff0000"
          showPlateOutline
          torchMode={Camera.constants.TorchMode.off}
          touchToFocus
        />
        <View style={styles.textContainer}>
          <Text style={styles.text}>{this.state.plate}</Text>
        </View>
      </View>

    );
  }
}