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

android/app/src/main/kotlin/io/openim/flutter/openim/MainActivity.kt

@@ -1,6 +1,7 @@
 package io.openim.flutter.openim
 
 import android.content.Intent
+import android.app.Activity
 import android.content.pm.PackageInfo
 import android.content.pm.PackageManager
 import android.graphics.Bitmap
@@ -23,8 +24,11 @@ import java.io.File
 class MainActivity : FlutterActivity() {
     private val CHANNEL = "io.openim.flutter.openim/apk_info"
     private val SHELL_BRANDING_CHANNEL = "io.openim.flutter.im_webview_app/shell_branding"
+    private val FILE_PICKER_CHANNEL = "io.openim.flutter.openim/file_picker"
     private val TAG = "MainActivity"
     private val MAX_BRANDING_ICON_SIZE = 192
+    private val FILE_PICKER_REQUEST_CODE = 4201
+    private var pendingFilePickerResult: MethodChannel.Result? = null
 
     override fun onCreate(savedInstanceState: android.os.Bundle?) {
         // 华为/荣耀/OPPO 等国产设备：在任意网络请求之前同步安装 Conscrypt，修复 SSL 握手失败（无 GMS 时系统 SSL 实现不完整）
@@ -107,6 +111,137 @@ class MainActivity : FlutterActivity() {
                 }
             }
         }
+        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, FILE_PICKER_CHANNEL).setMethodCallHandler { call, result ->
+            when (call.method) {
+                "pickFiles" -> {
+                    val acceptTypes = call.argument<List<String>>("acceptTypes") ?: emptyList()
+                    val allowMultiple = call.argument<Boolean>("allowMultiple") ?: false
+                    openNativeFilePicker(acceptTypes, allowMultiple, result)
+                }
+                else -> {
+                    result.notImplemented()
+                }
+            }
+        }
+    }
+
+    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
+        if (requestCode == FILE_PICKER_REQUEST_CODE) {
+            val result = pendingFilePickerResult
+            pendingFilePickerResult = null
+            if (result == null) {
+                super.onActivityResult(requestCode, resultCode, data)
+                return
+            }
+
+            if (resultCode != Activity.RESULT_OK || data == null) {
+                result.success(emptyList<String>())
+                return
+            }
+
+            val uris = mutableListOf<String>()
+            val clipData = data.clipData
+            if (clipData != null) {
+                for (index in 0 until clipData.itemCount) {
+                    clipData.getItemAt(index).uri?.let { uri ->
+                        grantPickedFileReadPermission(uri)
+                        uris.add(uri.toString())
+                    }
+                }
+            } else {
+                data.data?.let { uri ->
+                    grantPickedFileReadPermission(uri)
+                    uris.add(uri.toString())
+                }
+            }
+            result.success(uris)
+            return
+        }
+
+        super.onActivityResult(requestCode, resultCode, data)
+    }
+
+    private fun openNativeFilePicker(
+        acceptTypes: List<String>,
+        allowMultiple: Boolean,
+        result: MethodChannel.Result
+    ) {
+        if (pendingFilePickerResult != null) {
+            result.error("FILE_PICKER_BUSY", "A file picker request is already active", null)
+            return
+        }
+
+        val mimeTypes = normalizeMimeTypes(acceptTypes)
+        val intent = Intent(Intent.ACTION_OPEN_DOCUMENT).apply {
+            addCategory(Intent.CATEGORY_OPENABLE)
+            type = when (mimeTypes.size) {
+                0 -> "*/*"
+                1 -> mimeTypes.first()
+                else -> "*/*"
+            }
+            putExtra(Intent.EXTRA_ALLOW_MULTIPLE, allowMultiple)
+            if (mimeTypes.size > 1) {
+                putExtra(Intent.EXTRA_MIME_TYPES, mimeTypes.toTypedArray())
+            }
+            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            addFlags(Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION)
+        }
+
+        pendingFilePickerResult = result
+        try {
+            startActivityForResult(
+                Intent.createChooser(intent, "选择文件"),
+                FILE_PICKER_REQUEST_CODE
+            )
+        } catch (e: Exception) {
+            pendingFilePickerResult = null
+            result.error("FILE_PICKER_ERROR", e.message ?: "Unable to open file picker", null)
+        }
+    }
+
+    private fun normalizeMimeTypes(acceptTypes: List<String>): List<String> {
+        val mimeTypes = linkedSetOf<String>()
+        acceptTypes
+            .map { it.trim().lowercase() }
+            .filter { it.isNotEmpty() && it != "*/*" }
+            .forEach { type ->
+                when {
+                    type.startsWith(".") -> mimeTypes.addAll(mimeTypesForExtension(type))
+                    type.contains("/") -> mimeTypes.add(type)
+                }
+            }
+        return mimeTypes.toList()
+    }
+
+    private fun mimeTypesForExtension(extension: String): List<String> {
+        return when (extension) {
+            ".jpg", ".jpeg" -> listOf("image/jpeg")
+            ".png" -> listOf("image/png")
+            ".gif" -> listOf("image/gif")
+            ".webp" -> listOf("image/webp")
+            ".heic" -> listOf("image/heic")
+            ".heif" -> listOf("image/heif")
+            ".mp4", ".m4v" -> listOf("video/mp4")
+            ".mov" -> listOf("video/quicktime")
+            ".webm" -> listOf("video/webm")
+            ".mp3" -> listOf("audio/mpeg")
+            ".m4a" -> listOf("audio/mp4")
+            ".aac" -> listOf("audio/aac")
+            ".wav" -> listOf("audio/wav")
+            else -> emptyList()
+        }
+    }
+
+    private fun grantPickedFileReadPermission(uri: Uri) {
+        try {
+            contentResolver.takePersistableUriPermission(
+                uri,
+                Intent.FLAG_GRANT_READ_URI_PERMISSION
+            )
+        } catch (_: Exception) {
+            // Not all providers grant persistable permissions. The transient
+            // read grant is enough for WebView's file upload handoff.
+        }
     }
 
     private fun getCurrentAppName(): String {

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