feat(APKUpdate): conditionally import native modules for APK updates on Android

- Implemented conditional imports for `expo-file-system` and `expo-intent-launcher` to ensure compatibility with non-Android environments.
- Added error handling to alert users when native modules are unavailable, directing them to download APKs via the browser.
- Enhanced the `installAPK` function to check for the availability of native modules before proceeding with installation.

src/services/apkUpdateService.ts

@@ -5,11 +5,22 @@
 
 import { Platform, Linking, Alert } from 'react-native';
 import Constants from 'expo-constants';
-import * as FileSystem from 'expo-file-system/legacy';
-import * as IntentLauncher from 'expo-intent-launcher';
 import AsyncStorage from '@react-native-async-storage/async-storage';
 import { showConfirm } from './dialogService';
 
+// 条件导入原生模块（仅在 Android 上可用）
+let FileSystem: typeof import('expo-file-system/legacy') | null = null;
+let IntentLauncher: typeof import('expo-intent-launcher') | null = null;
+
+if (Platform.OS === 'android') {
+  try {
+    FileSystem = require('expo-file-system/legacy');
+    IntentLauncher = require('expo-intent-launcher');
+  } catch (e) {
+    console.warn('Failed to load native modules for APK update:', e);
+  }
+}
+
 // 更新服务器地址
 const UPDATES_SERVER_URL = Constants.expoConfig?.extra?.updatesUrl
   ? Constants.expoConfig.extra.updatesUrl.replace('/api/manifest', '')
@@ -133,6 +144,12 @@ async function downloadAndInstallAPK(downloadUrl: string, version: string): Prom
     return;
   }
 
+  if (!FileSystem) {
+    Alert.alert('提示', '当前环境不支持 APK 更新，请在浏览器中下载');
+    Linking.openURL(downloadUrl);
+    return;
+  }
+
   try {
     const downloadPath = `${FileSystem.documentDirectory}carrot-bbs-${version}.apk`;
     
@@ -171,6 +188,10 @@ async function downloadAndInstallAPK(downloadUrl: string, version: string): Prom
  */
 async function installAPK(apkUri: string): Promise<void> {
   try {
+    if (!FileSystem || !IntentLauncher) {
+      throw new Error('Native modules not available');
+    }
+    
     // 获取文件的 content URI
     const contentUri = await FileSystem.getContentUriAsync(apkUri);
     
@@ -182,8 +203,7 @@ async function installAPK(apkUri: string): Promise<void> {
   } catch (error) {
     console.error('Install APK error:', error);
     // 尝试使用浏览器下载
-    const webUrl = apkUri.replace('file://', '');
-    Linking.openURL(webUrl);
+    Linking.openURL(apkUri.replace('file://', ''));
   }
 }