在我尝试在scanner.js中实现它之后

import React, { useState, useEffect,Component,onMount} from 'react';
import { Text,TextInput, View, StyleSheet, Button } from 'react-native';
import { BarCodeScanner } from 'expo-barcode-scanner';
import {useNavigation} from'@react-navigation/native';
import {StatusBar} from 'expo-status-bar';

  export default function Scanner () {

  const [hasPermission, setHasPermission] = useState(null);
  const [scanned, setScanned] = useState(false);
  const [userid, setText] = useState('Not yet scanned')
  const [currentDate, setCurrentDate] = useState('');
  const navigation = useNavigation();

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

  // Request Camera Permission
  useEffect(() => {
    askForCameraPermission();
  }, []);

  useEffect(() => {
    var date = new Date().getDate(); //Current Date
    var month = new Date().getMonth() + 1; //Current Month
    var year = new Date().getFullYear(); //Current Year
    var hours = new Date().getHours(); //Current Hours
    var min = new Date().getMinutes(); //Current Minutes
    var sec = new Date().getSeconds(); //Current Seconds
    setCurrentDate(
      date + '/' + month + '/' + year 
      + ' ' + hours + ':' + min + ':' + sec
    );
  }, []);
  // What happens when we scan the bar code

  const handleBarCodeScanned = ({ type, data }) => {

    setScanned(true);

     setText(data )

  };
  Register = () => {
    this.state={
        userid:''
    };
    let userid = this.state.userid;

      let InsertAPIURL = "https://127.0.0.1/api/insert.php";

      let headers = {
        'Accept': 'application/json',
        'Content-Type': 'application/json'
      };

      let Data = {
        userid: userid,

      };

      fetch(InsertAPIURL, {
        method: 'POST',
        headers: headers,
        body: JSON.stringify(Data)
      })
      .then((response) =>response.json())
      .then((response)=>{
        alert(response[0].Message);
      })
      .catch((error) => {
        alert("Eror"+error);
      })

  }

  // Check permissions and return the screens
  if (hasPermission === null) {
    return (
      <View style={styles.container}>
        <Text>Requesting for camera permission</Text>
      </View>)
  }
  if (hasPermission === false) {
    return (
      <View style={styles.container}>
        <Text style={{ margin: 10 }}>No access to camera</Text>
        <Button title={'Allow Camera'} onPress={() => askForCameraPermission()} />
      </View>)
  }

  // Return the View
  return (

    <View style={styles.container}>
      <View style={styles.barcodebox}>
        <BarCodeScanner
          onBarCodeScanned={scanned ? undefined : handleBarCodeScanned}
          style={{ height: 400, width: 400 }} />
      </View>

      <Text style={styles.maintext}>{userid + '\n'+currentDate}

      </Text>

      {
        scanned && <Button title={'Scan again?'} onPress={() => setScanned(false)} color='tomato' />

      }

      {
        scanned && <Button title={'OK'} onPress={Register} /> 

      }
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  maintext: {
    fontSize: 16,
    margin: 20,
  },
  barcodebox: {
    alignItems: 'center',
    justifyContent: 'center',
    height: 300,
    width: 300,
    overflow: 'hidden',
    borderRadius: 30,
    backgroundColor: 'tomato'
  }
});

insert.php

<?php
    $CN = mysqli_connect('127.0.0.1', 'root', '');
    $DB = mysqli_select_db($CN, 'iostest');

    $EncodedData = file_get_contents('php://input');
    $DecodedData = json_decode($EncodedData, true);

    $userid = $DecodedData['userid'];

    $insertMemberData = "insert into scan(user) values ('$userid')";

    $register = mysqli_query($CN, $insertMemberData);

    if ($register) 
        $Message = "Member has been registered successfully";
    else 
        $Message = "Server Error... please try latter";

    $Response[] = array("Message" => $Message);
    echo json_encode($Response);
?>

在我扫描条形码并单击“确定”按钮后显示错误typeError：网络请求失败