feat:调整了启动/首屏阶段的 WebView 和壳层 fallback 展示：

WebView 背景从白色改成透明。
WebView 不再无条件渲染，只有已发起初始加载或首屏已展示后才渲染。
首屏未 ready 时，用 shell cover/fallback 盖住 WebView，避免白屏或 WebView 空白层提前露出。
顶部安全区背景色跟随 shell 背景，减少状态栏区域闪白

android/app/build.gradle.kts

@@ -795,7 +795,7 @@ fun computeApplicationId(): String {
 
 android {
     namespace = "io.openim.flutter.openim"
-    compileSdk = flutter.compileSdkVersion
+    compileSdk = 36
     ndkVersion = "27.0.12077973" // 使用已存在的NDK版本，避免下载问题
 
     compileOptions {
@@ -948,7 +948,7 @@ android {
         
         // You can update the following values to match your application needs.
         // For more information, see: https://flutter.dev/to/review-gradle-config.
-        minSdk = flutter.minSdkVersion
+        minSdk = 23
         targetSdk = flutter.targetSdkVersion
         versionCode = flutter.versionCode
         versionName = flutter.versionName

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

@@ -16,6 +16,7 @@ import android.util.Base64
 import android.util.Log
 import android.view.View
 import android.view.ViewGroup
+import android.view.autofill.AutofillManager
 import android.webkit.CookieManager
 import android.webkit.WebStorage
 import android.webkit.WebView
@@ -59,6 +60,13 @@ class MainActivity : FlutterActivity() {
         disableAutofillForCurrentWindow()
     }
 
+    override fun onWindowFocusChanged(hasFocus: Boolean) {
+        super.onWindowFocusChanged(hasFocus)
+        if (hasFocus) {
+            disableAutofillForCurrentWindow()
+        }
+    }
+
     override fun onDestroy() {
         pendingCaptureConfirmationDialog?.dismiss()
         pendingCaptureConfirmationDialog = null
@@ -405,21 +413,18 @@ class MainActivity : FlutterActivity() {
     }
 
     private fun installAutofillBlocker() {
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
-            return
-        }
-
         disableAutofillForCurrentWindow()
         window.decorView.viewTreeObserver.addOnGlobalLayoutListener {
             disableAutofillForCurrentWindow()
         }
+        window.decorView.post {
+            disableAutofillForCurrentWindow()
+        }
     }
 
     private fun disableAutofillForCurrentWindow() {
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
-            return
-        }
         disableAutofill(window.decorView)
+        cancelAutofillSession()
     }
 
     private fun disableAutofill(view: View) {
@@ -427,6 +432,10 @@ class MainActivity : FlutterActivity() {
             view.importantForAutofill = View.IMPORTANT_FOR_AUTOFILL_NO_EXCLUDE_DESCENDANTS
         }
 
+        if (view is WebView) {
+            disableWebViewAutofill(view)
+        }
+
         if (view is ViewGroup) {
             for (index in 0 until view.childCount) {
                 disableAutofill(view.getChildAt(index))
@@ -434,6 +443,35 @@ class MainActivity : FlutterActivity() {
         }
     }
 
+    private fun disableWebViewAutofill(webView: WebView) {
+        webView.settings.setSaveFormData(false)
+        webView.clearFormData()
+        webView.isSaveEnabled = false
+        webView.setSaveFromParentEnabled(false)
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            webView.importantForAutofill =
+                View.IMPORTANT_FOR_AUTOFILL_NO_EXCLUDE_DESCENDANTS
+        }
+
+        webView.post {
+            webView.settings.setSaveFormData(false)
+            webView.clearFormData()
+            webView.isSaveEnabled = false
+            webView.setSaveFromParentEnabled(false)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                webView.importantForAutofill =
+                    View.IMPORTANT_FOR_AUTOFILL_NO_EXCLUDE_DESCENDANTS
+            }
+        }
+    }
+
+    private fun cancelAutofillSession() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            getSystemService(AutofillManager::class.java)?.cancel()
+        }
+    }
+
     private fun normalizeMimeTypes(acceptTypes: List<String>): List<String> {
         val mimeTypes = linkedSetOf<String>()
         acceptTypes

lib/config/app_config.dart

@@ -114,10 +114,11 @@ class AppConfig {
   }
 
   static String _randomWildcardLabel() {
-    final digits = StringBuffer(_random.nextInt(9) + 1);
+    const alphabet = 'abcdefghijklmnopqrstuvwxyz0123456789';
-    for (var index = 1; index < 16; index += 1) {
+    final label = StringBuffer();
-      digits.write(_random.nextInt(10));
+    for (var index = 0; index < 6; index += 1) {
+      label.write(alphabet[_random.nextInt(alphabet.length)]);
     }
-    return digits.toString();
+    return label.toString();
   }
 }

lib/main.dart

@@ -2,6 +2,8 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:flutter/foundation.dart';
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:permission_handler/permission_handler.dart';
@@ -17,28 +19,17 @@ const _shellAccent = Color(0xFF168CFF);
 const _shellAccentDeep = Color(0xFF0066D9);
 const _shellInk = Color(0xFF17233D);
 const _shellSubText = Color(0xFF7C8AA3);
-const _shellBrandingChannel =
+const _shellBrandingChannel = MethodChannel(
-    MethodChannel('io.openim.flutter.im_webview_app/shell_branding');
+  'io.openim.flutter.im_webview_app/shell_branding',
-const _androidFilePickerChannel =
+);
-    MethodChannel('io.openim.flutter.openim/file_picker');
+const _androidFilePickerChannel = MethodChannel(
-const _h5CacheChannel =
+  'io.openim.flutter.openim/file_picker',
-    MethodChannel('io.openim.flutter.im_webview_app/h5_cache');
+);
 const _keyboardAnimationDuration = Duration(milliseconds: 250);
-const _initialH5CacheClearedKey = 'initial_h5_cache_cleared_v1';
-const _h5DomainCacheDateKey = 'h5_random_domain_date_v1';
-const _h5DomainCacheSessionKey = 'h5_random_domain_session_v1';
 const _h5DomainCacheUrlKey = 'h5_random_domain_url_v1';
 const _lineProbeTimeout = Duration(seconds: 5);
 const _maxGeneratedLineAttempts = 6;
-final String _h5DomainProcessSession =
+const _longBackgroundRefreshThreshold = Duration(minutes: 20);
-    'session-${DateTime.now().microsecondsSinceEpoch}';
-
-String _domainDateKey(DateTime value) {
-  final year = value.year.toString().padLeft(4, '0');
-  final month = value.month.toString().padLeft(2, '0');
-  final day = value.day.toString().padLeft(2, '0');
-  return '$year-$month-$day';
-}
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -54,10 +45,7 @@ Future<void> main() async {
 }
 
 class ShellBranding {
-  const ShellBranding({
+  const ShellBranding({required this.appName, required this.appLogo});
-    required this.appName,
-    required this.appLogo,
-  });
 
   static const fallback = ShellBranding(
     appName: AppConfig.appName,
@@ -69,8 +57,9 @@ class ShellBranding {
 
   static Future<ShellBranding> load() async {
     try {
-      final data = await _shellBrandingChannel
+      final data = await _shellBrandingChannel.invokeMapMethod<String, String>(
-          .invokeMapMethod<String, String>('getShellBranding');
+        'getShellBranding',
+      );
       final appName = _trim(data?['appName']);
       final appLogo = _trim(data?['appLogo']);
 
@@ -86,17 +75,10 @@ class ShellBranding {
   static String _trim(String? value) => value?.trim() ?? '';
 }
 
-enum _LineAvailability {
+enum _LineAvailability { checking, available, unavailable }
-  checking,
-  available,
-  unavailable,
-}
 
 class ImWebViewApp extends StatelessWidget {
-  const ImWebViewApp({
+  const ImWebViewApp({super.key, this.shellBranding = ShellBranding.fallback});
-    super.key,
-    this.shellBranding = ShellBranding.fallback,
-  });
 
   final ShellBranding shellBranding;
 
@@ -125,6 +107,11 @@ class H5ShellPage extends StatefulWidget {
 }
 
 class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
+  static final Set<Factory<OneSequenceGestureRecognizer>>
+      _webViewGestureRecognizers = <Factory<OneSequenceGestureRecognizer>>{
+    Factory<EagerGestureRecognizer>(() => EagerGestureRecognizer()),
+  };
+
   late H5Line _h5Line;
   late _H5LineWebViewSlot _lineSlot;
 
@@ -136,10 +123,9 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
   int _keyboardSyncToken = 0;
   int _lineGeneration = 0;
   int _h5LineAttempt = 0;
+  int _resumeRecoveryToken = 0;
+  DateTime? _backgroundedAt;
   late ShellBranding _shellBranding;
-  Future<void>? _cacheClearTask;
-  Timer? _domainExpiryTimer;
-  String _activeDomainDateKey = '';
 
   _H5LineWebViewSlot get _currentSlot => _lineSlot;
 
@@ -150,7 +136,6 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     _h5Line = AppConfig.h5Line;
     _shellBranding = widget.initialShellBranding;
     _lineSlot = _createLineSlot(_h5Line);
-    _scheduleDomainExpiryTimer();
     unawaited(_initializeLines());
   }
 
@@ -171,19 +156,15 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
       ..setJavaScriptMode(JavaScriptMode.unrestricted)
       ..addJavaScriptChannel(
         'OpenIMShell',
-        onMessageReceived: (message) => _handleShellMessage(
+        onMessageReceived: (message) =>
-          generation,
+            _handleShellMessage(generation, message),
-          message,
-        ),
       )
       ..addJavaScriptChannel(
         'OpenIMFlutterShell',
-        onMessageReceived: (message) => _handleFlutterShellMessage(
+        onMessageReceived: (message) =>
-          generation,
+            _handleFlutterShellMessage(generation, message),
-          message,
-        ),
       )
-      ..setBackgroundColor(Colors.white)
+      ..setBackgroundColor(Colors.transparent)
       ..setNavigationDelegate(
         NavigationDelegate(
           onProgress: (progress) {
@@ -252,14 +233,12 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     }
 
     try {
-      final result = await _androidFilePickerChannel.invokeListMethod<String>(
+      final result = await _androidFilePickerChannel
-        'pickFiles',
+          .invokeListMethod<String>('pickFiles', {
-        {
         'acceptTypes': params.acceptTypes,
         'allowMultiple': params.mode == FileSelectorMode.openMultiple,
         'capture': params.isCaptureEnabled,
-        },
+      });
-      );
       return result ?? <String>[];
     } catch (_) {
       return <String>[];
@@ -269,20 +248,29 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
   @override
   void dispose() {
     WidgetsBinding.instance.removeObserver(this);
-    _domainExpiryTimer?.cancel();
     _lineSlot.dispose();
     super.dispose();
   }
 
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state == AppLifecycleState.paused ||
+        state == AppLifecycleState.inactive ||
+        state == AppLifecycleState.detached) {
+      _backgroundedAt ??= DateTime.now();
+      return;
+    }
+
     if (state == AppLifecycleState.resumed) {
-      unawaited(_refreshExpiredH5LinesIfNeeded());
+      final backgroundDuration = _backgroundedAt == null
+          ? Duration.zero
+          : DateTime.now().difference(_backgroundedAt!);
+      _backgroundedAt = null;
+      unawaited(_recoverWebViewAfterResume(backgroundDuration));
     }
   }
 
   Future<void> _initializeLines() async {
-    await _clearInitialH5CachesIfNeeded();
     await _prepareAndLoadH5Line(forceNew: false);
   }
 
@@ -307,7 +295,6 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
           _isPreparingInitialLine = false;
         });
         await _loadCurrentLine(forceReload: true);
-        _scheduleDomainExpiryTimer();
         return;
       }
 
@@ -323,40 +310,25 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
       _currentSlot.loadError = '当前线路暂不可用，请稍后重试';
       _currentSlot.showShellCover = false;
     });
-    _scheduleDomainExpiryTimer();
   }
 
-  Future<H5Line> _loadCachedOrCreateH5Line({
+  Future<H5Line> _loadCachedOrCreateH5Line({required bool forceNew}) async {
-    required bool forceNew,
-  }) async {
-    final today = _domainDateKey(DateTime.now());
-    _activeDomainDateKey = today;
-
     try {
       final preferences = await SharedPreferences.getInstance();
       final cachedUrl = preferences.getString(_h5DomainCacheUrlKey);
       final cachedLine =
           cachedUrl == null ? null : AppConfig.h5LineFromUrl(cachedUrl);
-      final canUseCachedLine = !forceNew &&
+      final canUseCachedLine = !forceNew && cachedLine != null;
-          preferences.getString(_h5DomainCacheDateKey) == today &&
-          preferences.getString(_h5DomainCacheSessionKey) ==
-              _h5DomainProcessSession &&
-          cachedLine != null;
 
       if (canUseCachedLine) {
-        _logH5Line('复用本进程当天随机线路', cachedLine);
+        _logH5Line('复用已保存 H5 线路', cachedLine);
         return cachedLine;
       }
 
       final line = AppConfig.createRandomH5Line(attempt: _h5LineAttempt);
       _h5LineAttempt += 1;
-      await preferences.setString(_h5DomainCacheDateKey, today);
-      await preferences.setString(
-        _h5DomainCacheSessionKey,
-        _h5DomainProcessSession,
-      );
       await preferences.setString(_h5DomainCacheUrlKey, line.url);
-      _logH5Line('生成当天随机线路', line);
+      _logH5Line('生成并保存 H5 线路', line);
       return line;
     } catch (_) {
       final line = AppConfig.createRandomH5Line(attempt: _h5LineAttempt);
@@ -366,132 +338,6 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     }
   }
 
-  Future<void> _refreshExpiredH5LinesIfNeeded() async {
-    final today = _domainDateKey(DateTime.now());
-    if (_isPreparingInitialLine || _activeDomainDateKey == today) {
-      _scheduleDomainExpiryTimer();
-      return;
-    }
-
-    if (mounted) {
-      setState(() {
-        _isPreparingInitialLine = true;
-      });
-    }
-
-    await _clearAllH5Caches();
-    await _prepareAndLoadH5Line(forceNew: true);
-  }
-
-  void _scheduleDomainExpiryTimer() {
-    _domainExpiryTimer?.cancel();
-
-    final now = DateTime.now();
-    final nextMidnight = DateTime(now.year, now.month, now.day + 1);
-    final delay = nextMidnight.difference(now) + const Duration(seconds: 1);
-    _domainExpiryTimer = Timer(
-      delay,
-      () => unawaited(_refreshExpiredH5LinesIfNeeded()),
-    );
-  }
-
-  Future<void> _clearInitialH5CachesIfNeeded() async {
-    try {
-      final preferences = await SharedPreferences.getInstance();
-      if (preferences.getBool(_initialH5CacheClearedKey) == true) {
-        return;
-      }
-
-      await _clearAllH5Caches();
-      await preferences.setBool(_initialH5CacheClearedKey, true);
-    } catch (_) {
-      await _clearAllH5Caches();
-    }
-  }
-
-  Future<void> _clearAllH5Caches() {
-    final runningTask = _cacheClearTask;
-    if (runningTask != null) {
-      return runningTask;
-    }
-
-    final task = _clearAllH5CachesInternal();
-    _cacheClearTask = task;
-    return task.whenComplete(() {
-      if (identical(_cacheClearTask, task)) {
-        _cacheClearTask = null;
-      }
-    });
-  }
-
-  Future<void> _clearAllH5CachesInternal() async {
-    await _clearNativeH5WebsiteData();
-    await _clearCookiesSafely();
-    await _clearPageStorage(_lineSlot.controller);
-    await _clearControllerStorage(_lineSlot.controller);
-  }
-
-  Future<void> _clearNativeH5WebsiteData() async {
-    try {
-      await _h5CacheChannel.invokeMethod<void>('clearAllWebsiteData');
-    } catch (_) {
-      // Older native shells may not expose the cache channel yet.
-    }
-  }
-
-  Future<void> _clearCookiesSafely() async {
-    try {
-      await WebViewCookieManager().clearCookies();
-    } catch (_) {
-      // Cookie clearing is best-effort across platform WebView implementations.
-    }
-  }
-
-  Future<void> _clearControllerStorage(WebViewController controller) async {
-    try {
-      await controller.clearCache();
-    } catch (_) {}
-
-    try {
-      await controller.clearLocalStorage();
-    } catch (_) {}
-  }
-
-  Future<void> _clearPageStorage(WebViewController controller) async {
-    const script = '''
-(() => {
-  try {
-    if ('caches' in window) {
-      caches.keys().then((keys) => Promise.all(keys.map((key) => caches.delete(key))));
-    }
-  } catch (_) {}
-  try {
-    if ('serviceWorker' in navigator) {
-      navigator.serviceWorker.getRegistrations()
-        .then((items) => Promise.all(items.map((item) => item.unregister())));
-    }
-  } catch (_) {}
-  try {
-    if (typeof indexedDB !== 'undefined' && indexedDB.databases) {
-      indexedDB.databases().then((databases) => {
-        databases.forEach((database) => {
-          if (database && database.name) {
-            indexedDB.deleteDatabase(database.name);
-          }
-        });
-      });
-    }
-  } catch (_) {}
-  try { window.localStorage.clear(); } catch (_) {}
-  try { window.sessionStorage.clear(); } catch (_) {}
-})();
-''';
-
-    try {
-      await controller.runJavaScript(script);
-    } catch (_) {}
-  }
-
   Future<bool> _probeCurrentLine() async {
     final generation = _lineGeneration;
     final line = _lineSlot.line;
@@ -629,6 +475,8 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
         _hideShellCover(generation);
       } else if (decoded is Map && decoded['type'] == 'keyboard-bridge-ready') {
         unawaited(_syncKeyboardState());
+      } else if (decoded is Map && decoded['type'] == 'openExternalUrl') {
+        unawaited(_openExternalUrl(decoded['url']?.toString()));
       }
     } catch (_) {
       if (message.message == 'first-screen-ready') {
@@ -666,6 +514,8 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
           unawaited(openAppSettings());
         case 'keyboard-bridge-ready':
           unawaited(_syncKeyboardState());
+        case 'openExternalUrl':
+          unawaited(_openExternalUrl(decoded['url']?.toString()));
       }
     } catch (_) {
       // Ignore malformed shell messages from web content.
@@ -802,6 +652,97 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     return _runJavaScriptSafely(script);
   }
 
+  Future<void> _notifyH5AppResumed(Duration backgroundDuration) {
+    final payload = jsonEncode({
+      'backgroundDurationMs': backgroundDuration.inMilliseconds,
+      'refreshedAt': DateTime.now().millisecondsSinceEpoch,
+    });
+    final script = '''
+(() => {
+  try {
+    const detail = $payload;
+    window.dispatchEvent(new CustomEvent('openim-shell-app-resumed', { detail }));
+  } catch (_) {}
+})();
+''';
+    return _runJavaScriptSafely(script);
+  }
+
+  Future<bool> _isH5RuntimeResponsive() async {
+    try {
+      final result = await _lineSlot.controller.runJavaScriptReturningResult(
+        '''
+(() => {
+  try {
+    return JSON.stringify({
+      marker: 'openim-h5-runtime-alive',
+      readyState: document.readyState,
+      href: window.location.href,
+      now: Date.now()
+    });
+  } catch (_) {
+    return 'openim-h5-runtime-error';
+  }
+})();
+''',
+      ).timeout(const Duration(seconds: 2));
+      return result.toString().contains('openim-h5-runtime-alive');
+    } catch (_) {
+      return false;
+    }
+  }
+
+  Future<Uri> _currentReloadUri({required bool cacheBust}) async {
+    String? currentUrl;
+    try {
+      currentUrl = await _lineSlot.controller.currentUrl();
+    } catch (_) {
+      currentUrl = null;
+    }
+
+    final parsedCurrentUrl =
+        currentUrl == null ? null : Uri.tryParse(currentUrl);
+    final uri = parsedCurrentUrl?.hasScheme == true
+        ? parsedCurrentUrl!
+        : Uri.parse(_lineSlot.line.url);
+
+    if (!cacheBust) {
+      return uri;
+    }
+
+    final queryParameters = Map<String, String>.from(uri.queryParameters)
+      ..['_shell_resume_ts'] = DateTime.now().millisecondsSinceEpoch.toString();
+    return uri.replace(queryParameters: queryParameters);
+  }
+
+  Future<void> _recoverWebViewAfterResume(Duration backgroundDuration) async {
+    final token = ++_resumeRecoveryToken;
+    final generation = _lineGeneration;
+    await _syncShellRequestUrl();
+    await _syncShellBranding();
+    await _syncKeyboardState();
+    await _notifyH5AppResumed(backgroundDuration);
+
+    if (!_isCurrentLineGeneration(generation) ||
+        token != _resumeRecoveryToken ||
+        backgroundDuration < _longBackgroundRefreshThreshold) {
+      return;
+    }
+
+    final responsive = await _isH5RuntimeResponsive();
+    if (!mounted ||
+        !_isCurrentLineGeneration(generation) ||
+        token != _resumeRecoveryToken) {
+      return;
+    }
+
+    _logH5LineDebug(
+      '后台 ${backgroundDuration.inMinutes} 分钟后恢复，'
+      '${responsive ? '刷新 WebView 以拉取最新 H5' : 'WebView JS 无响应，重载当前页'}',
+    );
+    await _reloadCurrentLine(forceRefresh: true);
+  }
+
   Future<void> _handleShellMediaPermissionRequest({
     required int generation,
     required String requestId,
@@ -907,7 +848,6 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
 
     _isReplacingUnavailableLine = true;
     try {
-      await _clearAllH5Caches();
       if (mounted) {
         setState(() {
           _isPreparingInitialLine = true;
@@ -943,7 +883,7 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     await _syncKeyboardState();
   }
 
-  Future<void> _reloadCurrentLine() async {
+  Future<void> _reloadCurrentLine({bool forceRefresh = false}) async {
     final slot = _currentSlot;
     if (slot.availability == _LineAvailability.unavailable ||
         slot.loadError != null) {
@@ -961,7 +901,11 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
       });
     }
 
-    if (slot.hasLoadedInitialRequest) {
+    if (forceRefresh) {
+      await slot.controller.loadRequest(
+        await _currentReloadUri(cacheBust: true),
+      );
+    } else if (slot.hasLoadedInitialRequest) {
       await slot.controller.reload();
     } else {
       await _loadCurrentLine();
@@ -972,6 +916,7 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     PlatformWebViewWidgetCreationParams params =
         PlatformWebViewWidgetCreationParams(
       controller: _lineSlot.controller.platform,
+      gestureRecognizers: _webViewGestureRecognizers,
     );
 
     if (_lineSlot.controller.platform is AndroidWebViewController) {
@@ -998,18 +943,52 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
       return NavigationDecision.prevent;
     }
 
-    const webSchemes = {'http', 'https', 'about', 'data'};
+    const inWebViewSchemes = {'about', 'data'};
-    if (webSchemes.contains(uri.scheme)) {
+    if (inWebViewSchemes.contains(uri.scheme) || _isCurrentH5Origin(uri)) {
       return NavigationDecision.navigate;
     }
 
+    if (uri.scheme == 'http' || uri.scheme == 'https') {
+      await _openExternalUri(uri);
+      return NavigationDecision.prevent;
+    }
+
+    await _openExternalUri(uri);
+    return NavigationDecision.prevent;
+  }
+
+  bool _isCurrentH5Origin(Uri uri) {
+    final currentUri = Uri.tryParse(_currentSlot.line.url);
+    if (currentUri == null) {
+      return false;
+    }
+
+    return uri.scheme == currentUri.scheme &&
+        uri.host == currentUri.host &&
+        uri.port == currentUri.port;
+  }
+
+  Future<void> _openExternalUrl(String? rawUrl) async {
+    final url = rawUrl?.trim();
+    if (url == null || url.isEmpty) {
+      return;
+    }
+
+    final uri = Uri.tryParse(url);
+    if (uri == null || !uri.hasScheme) {
+      return;
+    }
+
+    await _openExternalUri(uri);
+  }
+
+  Future<void> _openExternalUri(Uri uri) async {
     try {
       await launchUrl(uri, mode: LaunchMode.externalApplication);
     } catch (_) {
       // Ignore unsupported custom schemes so the WebView does not navigate to
       // an error page.
     }
-    return NavigationDecision.prevent;
   }
 
   Future<void> _handleBackNavigation() async {
@@ -1030,6 +1009,12 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
     final shouldPaintShellFallback =
         (_isPreparingInitialLine || currentSlot.isAwaitingFirstScreen) &&
             currentSlot.loadError == null;
+    final shouldPaintShellCover =
+        currentSlot.showShellCover && !currentSlot.hasPresentedFirstScreen;
+    final shouldPaintWebView = currentSlot.hasLoadedInitialRequest ||
+        currentSlot.hasPresentedFirstScreen;
+    final shellBackgroundColor =
+        shouldPaintShellFallback ? _shellBackground : Colors.white;
 
     return PopScope(
       canPop: false,
@@ -1039,22 +1024,20 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
         }
       },
       child: Scaffold(
-        backgroundColor: Colors.white,
+        backgroundColor: shellBackgroundColor,
         body: Stack(
           children: [
             SafeArea(
               bottom: false,
               child: Stack(
                 children: [
-                  if (shouldPaintShellFallback)
+                  if (shouldPaintShellFallback && !shouldPaintShellCover)
                     Positioned.fill(
                       child: _ShellFallback(progress: currentSlot.progress),
                     ),
-                  Positioned.fill(
+                  if (shouldPaintWebView)
-                    child: _buildWebViewWidget(),
+                    Positioned.fill(child: _buildWebViewWidget()),
-                  ),
+                  if (shouldPaintShellCover)
-                  if (currentSlot.showShellCover &&
-                      !currentSlot.hasPresentedFirstScreen)
                     Positioned.fill(
                       child: IgnorePointer(
                         child: _ShellFallback(progress: currentSlot.progress),
@@ -1083,8 +1066,7 @@ class _H5ShellPageState extends State<H5ShellPage> with WidgetsBindingObserver {
               right: 0,
               height: topInset,
               child: ColoredBox(
-                color:
+                color: shellBackgroundColor,
-                    shouldPaintShellFallback ? _shellBackground : Colors.white,
               ),
             ),
           ],
@@ -1107,10 +1089,7 @@ class _NativeMediaPermissionResult {
 }
 
 class _H5LineWebViewSlot {
-  _H5LineWebViewSlot({
+  _H5LineWebViewSlot({required this.line, required this.controller});
-    required this.line,
-    required this.controller,
-  });
 
   final H5Line line;
   final WebViewController controller;
@@ -1159,10 +1138,7 @@ class _ErrorPanel extends StatelessWidget {
                 style: Theme.of(context).textTheme.bodyMedium,
               ),
               const SizedBox(height: 20),
-              FilledButton(
+              FilledButton(onPressed: onRetry, child: const Text('重新加载')),
-                onPressed: onRetry,
-                child: const Text('重新加载'),
-              ),
             ],
           ),
         ),
@@ -1188,8 +1164,10 @@ class _ShellFallback extends StatelessWidget {
         builder: (context, constraints) {
           final markSize = (constraints.maxWidth * 0.34).clamp(116.0, 148.0);
           final contentTop = constraints.maxHeight * 0.28;
-          final progressWidth =
+          final progressWidth = (constraints.maxWidth * 0.32).clamp(
-              (constraints.maxWidth * 0.32).clamp(116.0, 152.0);
+            116.0,
+            152.0,
+          );
 
           return Align(
             alignment: Alignment.topCenter,
@@ -1318,11 +1296,7 @@ class _H5LoadingBackgroundPainter extends CustomPainter {
       ..shader = const LinearGradient(
         begin: Alignment.topCenter,
         end: Alignment.bottomCenter,
-        colors: [
+        colors: [Color(0xFFEAF7FF), Color(0xFFF8FCFF), Colors.white],
-          Color(0xFFEAF7FF),
-          Color(0xFFF8FCFF),
-          Colors.white,
-        ],
         stops: [0, 0.52, 1],
       ).createShader(pageRect);
     canvas.drawRect(pageRect, pagePaint);
@@ -1471,10 +1445,7 @@ class _BubbleCheckPainter extends CustomPainter {
       ..shader = const LinearGradient(
         begin: Alignment.topLeft,
         end: Alignment.bottomRight,
-        colors: [
+        colors: [Color(0xFFE8FBF8), Color(0xFFAEECE4)],
-          Color(0xFFE8FBF8),
-          Color(0xFFAEECE4),
-        ],
       ).createShader(backBubble.outerRect);
     canvas.drawRRect(backBubble, backBubblePaint);
 
@@ -1499,11 +1470,7 @@ class _BubbleCheckPainter extends CustomPainter {
       ..shader = const LinearGradient(
         begin: Alignment.topLeft,
         end: Alignment.bottomRight,
-        colors: [
+        colors: [Color(0xFFA8DDFF), _shellAccent, _shellAccentDeep],
-          Color(0xFFA8DDFF),
-          _shellAccent,
-          _shellAccentDeep,
-        ],
         stops: [0, 0.48, 1],
       ).createShader(frontRect);
     canvas.drawPath(frontTail, bubblePaint);