How to scan one barcode per time? [react-native-camera]

Actually i'm new to React and i'm trying to make a simple barcode scanner which show the scanned barcode in an alert and after pressing "OK" in the alert the user should be able to scan another barcode.

The issue is that the barcode is continuously scanned and when the alert is up it's hiding and showing every second the alert.

I was trying to do something like this to show the alert only once and if OK is pressed to be able to show again the alert but only in case the OK is pressed but that had no effect..

  onBarCodeRead = (e) => {
    if(!this.alertPresent){
      this.alertPresent = true;
          Alert.alert(
            "Barcode type is " + e.type,
            "Barcode value is " + e.data,
            [
                 {text: 'OK', onPress: () => this.alertPresent = false;},
            ],
              {cancelable: false},
          );
      }
  }

Here is full code of Barcode.JS

import React, { Component } from 'react';
import { Button, Text, View,Alert } from 'react-native';
import { RNCamera } from 'react-native-camera';
import BarcodeMask from 'react-native-barcode-mask';
class ProductScanRNCamera extends Component {

  constructor(props) {
    super(props);
    this.camera = null;
    this.barcodeCodes = [];
    this.alertPresent = false;
    this.state = {
      camera: {
        flashMode: RNCamera.Constants.FlashMode.auto,
      }
    };
  }

  onBarCodeRead = (e) => {
    if(!this.alertPresent){
      this.alertPresent = true;
          Alert.alert(
            "Barcode type is " + e.type,
            "Barcode value is " + e.data,
            [
                 {text: 'OK', onPress: () => this.alertPresent = false;},
            ],
              {cancelable: false},
          );
      }
  }


  pendingView() {
    return (
      <View
      style={{
        flex: 1,
        backgroundColor: 'lightgreen',
        justifyContent: 'center',
        alignItems: 'center',
      }}
      >
      <Text>Waiting</Text>
      </View>
    );
  }

  render() {


    return (
      <View style={styles.container}>
      <RNCamera
      ref={ref => {
        this.camera = ref;
      }}
      defaultTouchToFocus
      flashMode={this.state.camera.flashMode}
      mirrorImage={false}
      onBarCodeRead={this.onBarCodeRead.bind(this)}
      onFocusChanged={() => {}}
      onZoomChanged={() => {}}
      style={styles.preview}
      >
      <BarcodeMask/>
      </RNCamera>
      </View>
    );
  }
}