feat: 添加 Android 文件选择器支持，更新 H5ShellPage 以集成文件选择功能

lib/main.dart

@@ -6,6 +6,7 @@ import 'package:flutter/services.dart';
 import 'package:permission_handler/permission_handler.dart';
 import 'package:url_launcher/url_launcher.dart';
 import 'package:webview_flutter/webview_flutter.dart';
+import 'package:webview_flutter_android/webview_flutter_android.dart';
 
 import 'config/app_config.dart';
 
@@ -14,6 +15,8 @@ const _shellAccent = Color(0xFF0089FF);
 const _shellSubText = Color(0xFF8E9AB0);
 const _shellBrandingChannel =
     MethodChannel('io.openim.flutter.im_webview_app/shell_branding');
+const _androidFilePickerChannel =
+    MethodChannel('io.openim.flutter.openim/file_picker');
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -120,7 +123,7 @@ class _H5ShellPageState extends State<H5ShellPage> {
   }
 
   WebViewController _buildController(int lineIndex) {
-    return WebViewController(
+    final controller = WebViewController(
       onPermissionRequest: (request) {
         unawaited(_handleWebViewPermissionRequest(request));
       },
@@ -176,6 +179,39 @@ class _H5ShellPageState extends State<H5ShellPage> {
           onNavigationRequest: _handleNavigationRequest,
         ),
       );
+
+    _configurePlatformController(controller);
+    return controller;
+  }
+
+  void _configurePlatformController(WebViewController controller) {
+    final platformController = controller.platform;
+    if (platformController is AndroidWebViewController) {
+      unawaited(
+        platformController.setOnShowFileSelector(_handleAndroidFileSelection),
+      );
+    }
+  }
+
+  Future<List<String>> _handleAndroidFileSelection(
+    FileSelectorParams params,
+  ) async {
+    if (params.mode == FileSelectorMode.save) {
+      return <String>[];
+    }
+
+    try {
+      final result = await _androidFilePickerChannel.invokeListMethod<String>(
+        'pickFiles',
+        {
+          'acceptTypes': params.acceptTypes,
+          'allowMultiple': params.mode == FileSelectorMode.openMultiple,
+        },
+      );
+      return result ?? <String>[];
+    } catch (_) {
+      return <String>[];
+    }
   }
 
   @override