[[oktatas:telefon:react_native|< React Native]]

====== BarCodeScanner ======

  * **Szerző:** Sallai András
  * Copyright (c) Sallai András, 2023
  * Licenc: [[https://creativecommons.org/licenses/by-sa/4.0/|CC Attribution-Share Alike 4.0 International]]
  * Web: https://szit.hu

===== Telepítés =====

A BarCodeScanner telepítése:

  npx expo install expo-barcode-scanner


===== Alap példa =====

A következő példa egy másolat a következő oldalról, magyar nyelvre átírva:
  * https://docs.expo.dev/versions/v48.0.0/sdk/bar-code-scanner/

<code javascript App.js>
import { BarCodeScanner } from 'expo-barcode-scanner';
import { StatusBar } from 'expo-status-bar';
import { useEffect, useState } from 'react';
import { Button, StyleSheet, Text, View } from 'react-native';

export default function App() {

  const [hasPermission, setHasPermission] = useState(null);
  const [scanned, setScanned] = useState(false);
  
  useEffect(() => {
    const getBarCodeScannerPermissions = async () => {
      const { status } = await BarCodeScanner.requestPermissionsAsync();
      setHasPermission(status === 'granted');
    };
    getBarCodeScannerPermissions();
  }, []);

  const handleBarCodeScanned = ({ type, data }) => {
    setScanned(true);
    alert(`A vonalkód típusa ${type}\nAz olvasott adat: ${data}`);
  };

  if (hasPermission === null) {
    return <Text>Szükséges a kamerához hozzáférés</Text>;
  }
  if (hasPermission === false) {
    return <Text>A kamera nem elérhető</Text>;
  }  
  
  return (
    <View style={styles.container}>
      <BarCodeScanner
        onBarCodeScanned={scanned ? undefined : handleBarCodeScanned}
        style={StyleSheet.absoluteFillObject}
      />

      {scanned && <Button title={'Koppints az újabb szkenneléshez'} onPress={() => setScanned(false)} />}
      

      <StatusBar style="auto" />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

</code>

===== Bővített példa =====

A kamera-olvasó nem jelenik meg azonnal. Gombnyomásra indul.

<code javascript App.js>
import { BarCodeScanner } from 'expo-barcode-scanner';
import { StatusBar } from 'expo-status-bar';
import { useEffect, useState } from 'react';
import { Button, StyleSheet, Text, View } from 'react-native';

export default function App() {

  const [hasPermission, setHasPermission] = useState(null);
  const [scanned, setScanned] = useState(false);
  const [scanning, setScanning] = useState(false);

  useEffect(() => {
    const getBarCodeScannerPermissions = async () => {
      const { status } = await BarCodeScanner.requestPermissionsAsync();
      setHasPermission(status === 'granted');
    };

    getBarCodeScannerPermissions();
  }, []);

  const handleBarCodeScanned = ({ type, data }) => {
    setScanned(true);
    alert(`A vonalkód típusa ${type}\nAz olvasott adat: ${data}`);
  };

  if (hasPermission === null) {
    return <Text>Szükséges a kamerához hozzáférés</Text>;
  }
  if (hasPermission === false) {
    return <Text>A kamera nem elérhető</Text>;
  }  
  
  return (
    <View style={styles.container}>
      <Text>A "Szkennelés" gombra kattintva elindual a QR-kód szkenner.</Text>
      <Button title={'Szkennelés'} onPress={() => setScanning(true)}/>
      {
        scanning &&
        <BarCodeScanner
          onBarCodeScanned={scanned ? undefined : handleBarCodeScanned}
          style={StyleSheet.absoluteFillObject}
        />
      }
      {(scanned && scanning) && <Button title={'Tap to Scan Again'} onPress={() => setScanned(false)} />}
      {scanning && <Button title={'Bezár'} onPress={() => setScanning(false)} />}

      <StatusBar style="auto" />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

</code>

===== Linkek =====

  * https://www.qrcode.com/en/ (2023)