expo-easy-fs

A file utility for Expo to access the system Downloads folder, Android-only.

Android 权限与兼容性 (Permissions & Compatibility)

从 vX.X.X 版本开始(包含此修改)，expo-easy-fs 适配 Android 各版本存储策略：

Android 版本	存储模型	需要的权限 / 配置	说明
API < 29 (Android 9 及以下)	Legacy 外部存储	必须在 AndroidManifest.xml 中声明 READ_EXTERNAL_STORAGE 与 WRITE_EXTERNAL_STORAGE，并在运行时申请（WRITE 为必需）。	直接写入公共 Downloads 目录，需要用户授予权限。
API 29 (Android 10)	Scoped Storage (过渡)	无需 WRITE 权限；若要保持旧行为可加 requestLegacyExternalStorage=true（不推荐）。	本库使用 MediaStore 写入 Downloads 集合，无需额外权限。
API 30+ (Android 11 及以上)	Scoped Storage	无需 WRITE_EXTERNAL_STORAGE；普通下载不需要 MANAGE_EXTERNAL_STORAGE。	使用 MediaStore，系统自动管理。

需要在 Expo / React Native 项目中配置的 Manifest 权限

如果你仍需要兼容 Android 9 及以下，请在 app.json 或 app.config.js 中添加：

"android": {
  "permissions": [
    "READ_EXTERNAL_STORAGE",
    "WRITE_EXTERNAL_STORAGE"
  ]
}

并在运行时（仅 API <29）调用：

import { PermissionsAndroid, Platform } from 'react-native';

async function ensureLegacyStoragePermission() {
  if (Platform.OS === 'android' && Platform.Version < 29) {
    const granted = await PermissionsAndroid.request(
      PermissionsAndroid.PERMISSIONS.WRITE_EXTERNAL_STORAGE,
      {
        title: '存储权限',
        message: '需要存储权限以便保存文件到下载目录',
        buttonPositive: '确定'
      }
    );
    if (granted !== PermissionsAndroid.RESULTS.GRANTED) {
      throw new Error('WRITE_EXTERNAL_STORAGE denied');
    }
  }
}

提示：Android 13 (API 33) 引入了细化的媒体权限（如 READ_MEDIA_IMAGES 等），由于本库写入的是通用文件（可能是任意类型），通常无需这些媒体读取权限；下载后若你再读取/处理特定媒体类型，按需自行申请。

使用注意 (Notes)

1. 在 Android 10+ 上，本库通过 MediaStore 写入公共 Downloads，不需要手动申请写权限。
2. 旧方法 copyFileToDownload 现在接受 content://、file:// 或绝对路径，内部自动适配。
3. 如果你使用的是 Expo Managed Workflow，请确保构建时所需的权限都在配置里列出，否则旧设备上会失败。
4. 不要为仅保存普通下载文件去申请 MANAGE_EXTERNAL_STORAGE（All files access），那会触发应用上架审核风险。
5. 若你的源文件来自 expo-file-system，传入前可用本库的 fixPath 处理前缀。

新增/更新行为 (Changelog 摘要)

• 增强 copyFileToDownload：支持 Android 10+ Scoped Storage (MediaStore) 与旧版直写逻辑。
• 自动判断输入是 content://、file:// 还是普通路径。
• 根据文件扩展名推断 MIME Type，提升在系统文件管理器中的可见性。
• 对 API <29 若无写权限会直接抛出 ERR_PERMISSION_DENIED。

最低示例（含权限处理）

import * as ExpoEasyFs from 'expo-easy-fs';
import * as FileSystem from 'expo-file-system';

async function demo() {
  await ensureLegacyStoragePermission(); // 仅旧设备需要
  const filename = 'demo.txt';
  const localPath = FileSystem.documentDirectory + filename;
  await FileSystem.writeAsStringAsync(localPath, 'Hello');
  const { downloads } = await ExpoEasyFs.getPaths();
  await ExpoEasyFs.copyFile(localPath, `${downloads}/demo-folder/${filename}`);
}

---

Installation

npm install expo-easy-fs

API

/**
 * Retrieves system paths such as the downloads directory.
 * @returns {Promise<{ downloads: string }>} A promise resolving to an object containing the downloads path.
 */
export function getPaths(): Promise<{
  downloads: string;
}> {
  return ExpoEasyFsModule.getPaths();
}

/**
 * Creates a new directory.
 * @param {string} dirPath - The path of the directory to create.
 * @returns {Promise<string>} A promise resolving to the created directory's path.
 */
export function mkdir(dirPath: string): Promise<string> {
  return ExpoEasyFsModule.mkdir(fixPath(dirPath));
}

/**
 * Copies a file from the source path to the destination path.
 * @param {string} sourcePath - The source file path.
 * @param {string} destinationPath - The destination file path.
 * @returns {Promise<string>} A promise resolving to the destination file's path.
 */
export function copyFile(sourcePath: string, destinationPath: string): Promise<string> {
  return ExpoEasyFsModule.copyFile(fixPath(sourcePath), fixPath(destinationPath));
}

/**
 * Deletes a file or directory.
 * @param {string} targetPath - The path of the file or directory to delete.
 * @returns {Promise<string>} A promise resolving to the deleted target's path.
 */
export function remove(targetPath: string): Promise<string> {
  return ExpoEasyFsModule.remove(fixPath(targetPath));
}

/**
 * Checks if a path exists and returns its type.
 * @param {string} targetPath - The path to check.
 * @returns {Promise<{ exists: boolean, type: 'file' | 'directory' | 'unknown', path: string }>} 
 * A promise resolving to an object indicating existence, type, and the path.
 */
export function exists(targetPath: string): Promise<{
  exists: boolean;
  type: 'file' | 'directory' | 'unknown';
  path: string;
}> {
  return ExpoEasyFsModule.exists(fixPath(targetPath));
}

Example

import * as ExpoEasyFs from "expo-easy-fs";
import * as fileSystem from "expo-file-system";
import { StyleSheet, Text, View, StatusBar, Button } from "react-native";
import { useCallback } from "react";

export default function App() {
  const func = useCallback(async () => {
    try {
      const filename = `expo-easy-fs-${Date.now()}.txt`;
      const originFilePath = fileSystem.documentDirectory + filename;

      const { downloads: systemDownloadsDir } = await ExpoEasyFs.getPaths();

      const destinationDirPath = systemDownloadsDir + `/expo-easy-fs/`;
      const destinationFilePath = destinationDirPath + filename;

      await fileSystem.writeAsStringAsync(originFilePath, "Test");
      await ExpoEasyFs.mkdir(destinationDirPath);
      await ExpoEasyFs.copyFile(originFilePath.replace(/^file:\//, ""), destinationFilePath);
      await ExpoEasyFs.remove(originFilePath);
      alert(`Success! The test file has been created and moved to: ${destinationFilePath}`);
    } catch (err) {
      console.error(err);
      alert("An error occurred while processing the file. Please try again.");
    }
  }, []);

  return (
    <View style={styles.container}>
      <StatusBar barStyle="dark-content" />
      <Text>Welcome to the Expo Easy FS Demo</Text>
      <Button
        title="Create a file and move it to the system's Downloads folder"
        onPress={func}
      />
    </View>
  );
}

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