Expo React Native，将 PDF 文件保存到“下载”文件夹

以下代码适用于图像文件。但是当我尝试保存 PDF 文件或其他非媒体格式时，我得到无法创建资产 error.
我明白那个世博媒体库旨在处理媒体格式文件。 有没有什么替代方案世博媒体库保存其他文件格式？

import * as FileSystem from 'expo-file-system'
import * as Permissions from 'expo-permissions'
import * as MediaLibrary from 'expo-media-library'

const downloadFile = async (uri: string) => {
    const targetUri = FileSystem.documentDirectory + getFileName(uri)

    const downloadedFile = await FileSystem.downloadAsync(uri, targetUri)

    if (downloadedFile.status === 200) {
        if (Platform.OS === 'android') {
            const permission = await Permissions.askAsync(Permissions.MEDIA_LIBRARY)

            if (permission.status !== 'granted') {
                return
            }

            const asset = await MediaLibrary.createAssetAsync(downloadedFile.uri)
            const album = await MediaLibrary.getAlbumAsync('Download')

            await MediaLibrary.addAssetsToAlbumAsync([asset], album, false)
        }
    }
}

它适用于 Android 设备https://docs.expo.dev/versions/latest/sdk/filesystem/#storageaccessframeworkcreatefileasyncparenturi-string-filename-string-mimetype-string

import * as FileSystem from 'expo-file-system';
import { StorageAccessFramework } from 'expo-file-system';

const permissions = await StorageAccessFramework.requestDirectoryPermissionsAsync();
if (!permissions.granted) {
    return;
}

try {
    await StorageAccessFramework.createFileAsync(permissions.directoryUri, fileName, 'application/pdf')
    .then((r) => {
        console.log(r);
    })
    .catch((e) => {
        console.log(e);
    });
} catch((e) => {
    console.log(e);
});

我的pdf已经下载好了！

就我而言，我必须从 Base64 字符串生成文件。 我的代码：

import * as FileSystem from 'expo-file-system';
import { StorageAccessFramework } from 'expo-file-system';

const permissions = await StorageAccessFramework.requestDirectoryPermissionsAsync();
if (!permissions.granted) {
    return;
}

const base64Data = 'my base 64 data';

try {
    await StorageAccessFramework.createFileAsync(permissions.directoryUri, fileName, 'application/pdf')
        .then(async(uri) => {
            await FileSystem.writeAsStringAsync(uri, base64Data, { encoding: FileSystem.EncodingType.Base64 });
        })
        .catch((e) => {
            console.log(e);
        });
} catch (e) {
    throw new Error(e);
}