我尝试在iOS上使用由create-react-native-app创建的React Native应用程序录制音频。我正在使用expo-av库进行录制。但是，当我按下“开始录制”时，它立即崩溃。通过一些console.log语句，我发现它发生在“请求权限”之后，但在“开始录制”之前。这在Android上运行良好。附件是我的代码。为什么会发生这种情况？

import React, {useEffect, useState, setState} from 'react';
import {AsyncStorage, FlatList} from 'react-native';
import { Button, Layout, Text, Card } from '@ui-kitten/components';
import styles from './../../util/styles';
import {Audio} from 'expo-av';
import RNFS from 'react-native-fs';

export default function Record({navigation}) {
    const [recording, setRecording] = useState();

    const REC_OPT = {
        isMeteringEnabled: true,
        android: {
          extension: '.m4a',
          outputFormat: Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_MPEG_4,
          audioEncoder: Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AAC,
          sampleRate: 16000,
          numberOfChannels: 1,
          bitRate: 128000,
        },
        ios: {
          extension: '.wav',
          audioQuality: Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_MAX,
          sampleRate: 16000,
          numberOfChannels: 1
        },
    };
  
    async function startRecording() {
        try {
            console.log('Requesting permissions... ');
            await Audio.requestPermissionsAsync();
            await Audio.setAudioModeAsync({
                allowsRecordingIOS: true,
                playsInSilentModeIOS: true,
            }); 
            console.log('Starting recording..');
            const recording = new Audio.Recording();
            await recording.prepareToRecordAsync(REC_OPT);
            await recording.startAsync(); 
            setRecording(recording);
            console.log('Recording started');
        } catch (err) {
            console.error('Failed to start recording', err);
        }
    }
  
    async function stopRecording() {
        console.log('Stopping recording..');
        setRecording(undefined);
        await recording.stopAndUnloadAsync();
        const uri = recording.getURI(); 
        console.log('Recording stopped and stored at', uri);

        const fileArray = uri.split("/");
        const filename = fileArray[fileArray.length - 1];

        const newFilepath = RNFS.DocumentDirectoryPath + "/" + filename;
        console.log("old filepath: ", uri, " new filepath: ", filename, " document directory ", RNFS.DocumentDirectoryPath, " file array ", fileArray, " file array length ", fileArray.length, " fullFilepath ", newFilepath);

        await RNFS.copyFile(uri, newFilepath);

        try {
            var value = await AsyncStorage.getItem('FILES');
            if(value !== null){
                console.log("existing data");
            } else {
                value = "{}";
            }

            var rString = randomString(32, '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ');

            var json = JSON.parse(value);

            json[rString] = {"file_path": newFilepath, "name": rString, "id": rString, "analyzed": false, "analysis": {}};

            var jsonString = JSON.stringify(json);

            // console.log("update file: FILES " + jsonString);

            await AsyncStorage.setItem("FILES", jsonString);


            navigation.navigate('Home', {refresh: true});
        } catch (error) {
        console.error("failed to start recording", error);
        }
    }

    randomString = (length, chars) => {
        var result = '';
        for (var i = length; i > 0; --i) result += chars[Math.floor(Math.random() * chars.length)];
        return result;
    }
  
    return (
        <Layout style={styles.container}>
            <Button
            onPress={recording ? stopRecording : startRecording}
            >
                {recording ? 'Stop Recording' : 'Start Recording'}
            </Button>
        </Layout>
    );
}