would not learn the QR codes on my smartphones. how can I do?

import React, { useState, useEffect } from 'react';
import { View, StyleSheet, Button, Textual content, Alert } from 'react-native';
import { Digicam } from 'expo-camera';

const types = StyleSheet.create({
  container: {
    flex: 1,
    flexDirection: 'column',
    justifyContent: 'flex-end',
  },
  preview: {
    flex: 1,
    justifyContent: 'middle',
    alignItems: 'middle',
  },
  scanText: {
    fontSize: 20,
    textAlign: 'middle',
    margin: 10,
  },
  qrFrame: {
    width: 150,  // Riduci ulteriormente le dimensioni del riquadro
    peak: 150,
    borderRadius: 10,
    borderColor: '#FFF',
    borderWidth: 2,
    place: 'absolute',
    justifyContent: 'middle',
    alignItems: 'middle',
  },
  qrCodeText: {
    fontSize: 16,  // Riduci la dimensione del testo
    textAlign: 'middle',
    coloration: '#FFF',
  },
});

export default operate App() {
  const [hasCameraPermission, setHasCameraPermission] = useState(null);
  const [scanned, setScanned] = useState(false);
  const [scannedData, setScannedData] = useState('');
  const [serverResponse, setServerResponse] = useState('');

  useEffect(() => {
    (async () => {
      const { standing } = await Digicam.requestCameraPermissionsAsync();
      setHasCameraPermission(standing === 'granted');
    })();
  }, []);

  const handleBarCodeScanned = async ({ knowledge }) => {
    setScanned(true);
    setScannedData(`Dati: ${knowledge}`);

    // Ship knowledge to PHP server
    strive {
      const response = await fetch('https://www.chesifastasera.com/handleQR.php', {
        methodology: 'POST',
        headers: {
          Settle for: 'software/json',
          'Content material-Kind': 'software/json',
        },
        physique: JSON.stringify({ qrData: knowledge }), // Ship knowledge as JSON
      });

      if (!response.okay) {
        throw new Error(`HTTP Error! Code: ${response.standing}`);
      }

      const responseData = await response.textual content();
      setServerResponse(responseData); // Set server response in state

      // Show the response in an alert or different means
      Alert.alert('Server Response', responseData);

      // Different actions based mostly on server response right here

    } catch (error) {
      console.error('Error throughout server request:', error.message);
      // Error dealing with if wanted
    }
  };

  const resetScanner = () => {
    setScanned(false);
    setScannedData('');
    setServerResponse('');
  };

  if (hasCameraPermission === null) {
    return <View />;
  }
  if (hasCameraPermission === false) {
    return <Textual content>Digicam permission denied</Textual content>;
  }

  return (
    <View type={types.container}>
      <Digicam
        onBarCodeScanned={scanned ? undefined : handleBarCodeScanned}
        type={types.preview}
      >
        {/* Body the QR code right here */}
        <View type={types.qrFrame}>
          <Textual content type={types.qrCodeText}>{scannedData}</Textual content>
        </View>
      </Digicam>
      {scanned && (
        <View>
          <Textual content type={types.scanText}>{`Risposta del server: ${serverResponse}`}</Textual content>
          <Button title="Scansiona di nuovo" onPress={resetScanner} />
        </View>
      )}
    </View>
  );
}