feat: 增加AI配置文件与TTS自动朗读，修复二级页面返回按钮与音频播放

kouyu_english/lib/features/shell/learning_shell.dart

@@ -1,17 +1,17 @@
-import 'package:flutter/material.dart';
+import "package:flutter/material.dart";
 
-import '../../core/app_state.dart';
-import '../../core/app_theme.dart';
-import '../../core/models.dart';
-import '../../core/seed_courses.dart';
-import '../../core/assessment_bank.dart';
-import '../../widgets/app_widgets.dart';
-import '../dialogue/dialogue_flow.dart';
-import '../assessment/assessment_page.dart';
-import '../home/home_page.dart';
-import '../lesson/lesson_flow.dart';
-import '../progress/progress_pages.dart';
-import '../review/review_page.dart';
+import "../../core/app_state.dart";
+import "../../core/app_theme.dart";
+import "../../core/models.dart";
+import "../../core/seed_courses.dart";
+import "../../core/assessment_bank.dart";
+import "../../widgets/app_widgets.dart";
+import "../dialogue/dialogue_flow.dart";
+import "../assessment/assessment_page.dart";
+import "../home/home_page.dart";
+import "../lesson/lesson_flow.dart";
+import "../progress/progress_pages.dart";
+import "../review/review_page.dart";
 
 class LearningShell extends StatefulWidget {
   const LearningShell({super.key, required this.state});
@@ -24,6 +24,7 @@ class LearningShell extends StatefulWidget {
 class _LearningShellState extends State<LearningShell> {
   AppTab tab = AppTab.home;
   var route = _ShellRoute.tab;
+  _ShellRoute? previousRoute;
   bool dialogueInLesson = false;
   AssessmentPack? assessmentPack;
   DialogueSummaryData? dialogueSummary;
@@ -31,26 +32,86 @@ class _LearningShellState extends State<LearningShell> {
   void showTab(AppTab value) => setState(() {
     tab = value;
     route = _ShellRoute.tab;
+    previousRoute = null;
+  });
+
+  void showLesson() => setState(() {
+    previousRoute = route;
+    route = _ShellRoute.lesson;
+  });
+
+  void showDialogueScene() => setState(() {
+    previousRoute = route;
+    route = _ShellRoute.scene;
   });
 
-  void showLesson() => setState(() => route = _ShellRoute.lesson);
-  void showDialogueScene() => setState(() => route = _ShellRoute.scene);
   void showDialogue({bool inLesson = false}) => setState(() {
+    previousRoute = route;
     dialogueInLesson = inLesson;
     route = _ShellRoute.dialogue;
   });
+
   void showSummary(DialogueSummaryData summary) => setState(() {
+    previousRoute = route;
     dialogueSummary = summary;
     route = _ShellRoute.summary;
   });
-  void showSettings() => setState(() => route = _ShellRoute.settings);
+
+  void showSettings() => setState(() {
+    previousRoute = route;
+    route = _ShellRoute.settings;
+  });
+
   void showAssessment(AssessmentPack pack) => setState(() {
+    previousRoute = route;
     assessmentPack = pack;
     route = _ShellRoute.assessmentPreparation;
   });
-  void startAssessment() => setState(() => route = _ShellRoute.assessment);
-  void showAdaptiveLesson() =>
-      setState(() => route = _ShellRoute.adaptiveLesson);
+
+  void startAssessment() => setState(() {
+    previousRoute = route;
+    route = _ShellRoute.assessment;
+  });
+
+  void showAdaptiveLesson() => setState(() {
+    previousRoute = route;
+    route = _ShellRoute.adaptiveLesson;
+  });
+
+  void handleBack() {
+    switch (route) {
+      case _ShellRoute.lesson:
+        showTab(tab);
+      case _ShellRoute.scene:
+        showTab(tab);
+      case _ShellRoute.dialogue:
+        if (dialogueInLesson) {
+          showLesson();
+        } else if (previousRoute == _ShellRoute.scene) {
+          showDialogueScene();
+        } else {
+          showTab(tab == AppTab.dialogue ? AppTab.dialogue : tab);
+        }
+      case _ShellRoute.summary:
+        showTab(tab);
+      case _ShellRoute.settings:
+        showTab(AppTab.progress);
+      case _ShellRoute.adaptiveLesson:
+        showTab(AppTab.review);
+      case _ShellRoute.assessmentPreparation:
+        showTab(AppTab.progress);
+      case _ShellRoute.assessment:
+        if (assessmentPack != null) {
+          showAssessment(assessmentPack!);
+        } else {
+          showTab(AppTab.progress);
+        }
+      case _ShellRoute.tab:
+        if (tab != AppTab.home) {
+          showTab(AppTab.home);
+        }
+    }
+  }
 
   @override
   Widget build(BuildContext context) {
@@ -60,19 +121,26 @@ class _LearningShellState extends State<LearningShell> {
         body = LessonFlow(
           state: widget.state,
           onOpenDialogue: () => showDialogue(inLesson: true),
-          onFinish: () => showTab(AppTab.home),
+          onFinish: () => showTab(tab),
         );
       case _ShellRoute.scene:
-        body = DialogueScenePage(onStart: showDialogue);
+        body = DialogueScenePage(
+          onStart: showDialogue,
+          onBack: () => showTab(tab),
+        );
       case _ShellRoute.dialogue:
         body = DialoguePage(
           state: widget.state,
           isLessonDialogue: dialogueInLesson,
-          onFinished: dialogueInLesson
-              ? (_) => showLesson()
-              : (summary) {
-                  if (summary != null) showSummary(summary);
-                },
+          onFinished: (summary) {
+            if (dialogueInLesson) {
+              showLesson();
+            } else if (summary != null) {
+              showSummary(summary);
+            } else {
+              handleBack();
+            }
+          },
         );
       case _ShellRoute.summary:
         body = DialogueSummaryPage(
@@ -80,9 +148,13 @@ class _LearningShellState extends State<LearningShell> {
           onHome: () => showTab(AppTab.home),
           onLesson: showLesson,
           onRetry: showDialogue,
+          onBack: () => showTab(tab),
         );
       case _ShellRoute.settings:
-        body = SettingsPage(state: widget.state);
+        body = SettingsPage(
+          state: widget.state,
+          onBack: () => showTab(AppTab.progress),
+        );
       case _ShellRoute.adaptiveLesson:
         body = AdaptiveLessonPage(
           state: widget.state,
@@ -106,45 +178,53 @@ class _LearningShellState extends State<LearningShell> {
         body = _tabContent();
     }
 
-    return AnimatedBuilder(
-      animation: widget.state,
-      builder: (context, _) => Scaffold(
-        body: body,
-        bottomNavigationBar: route == _ShellRoute.tab
-            ? NavigationBar(
-                selectedIndex: tab.index,
-                height: 70,
-                indicatorColor: AppColors.softGreen,
-                onDestinationSelected: (index) => showTab(AppTab.values[index]),
-                destinations: const [
-                  NavigationDestination(
-                    icon: Icon(Icons.home_outlined),
-                    selectedIcon: Icon(Icons.home),
-                    label: '首页',
-                  ),
-                  NavigationDestination(
-                    icon: Icon(Icons.menu_book_outlined),
-                    selectedIcon: Icon(Icons.menu_book),
-                    label: '学习',
-                  ),
-                  NavigationDestination(
-                    icon: Icon(Icons.chat_bubble_outline),
-                    selectedIcon: Icon(Icons.chat_bubble),
-                    label: '对话',
-                  ),
-                  NavigationDestination(
-                    icon: Icon(Icons.refresh_outlined),
-                    selectedIcon: Icon(Icons.refresh),
-                    label: '复习',
-                  ),
-                  NavigationDestination(
-                    icon: Icon(Icons.person_outline),
-                    selectedIcon: Icon(Icons.person),
-                    label: '我的',
-                  ),
-                ],
-              )
-            : null,
+    return PopScope(
+      canPop: route == _ShellRoute.tab && tab == AppTab.home,
+      onPopInvokedWithResult: (didPop, _) {
+        if (!didPop) {
+          handleBack();
+        }
+      },
+      child: AnimatedBuilder(
+        animation: widget.state,
+        builder: (context, _) => Scaffold(
+          body: body,
+          bottomNavigationBar: route == _ShellRoute.tab
+              ? NavigationBar(
+                  selectedIndex: tab.index,
+                  height: 70,
+                  indicatorColor: AppColors.softGreen,
+                  onDestinationSelected: (index) => showTab(AppTab.values[index]),
+                  destinations: const [
+                    NavigationDestination(
+                      icon: Icon(Icons.home_outlined),
+                      selectedIcon: Icon(Icons.home),
+                      label: "首页",
+                    ),
+                    NavigationDestination(
+                      icon: Icon(Icons.menu_book_outlined),
+                      selectedIcon: Icon(Icons.menu_book),
+                      label: "学习",
+                    ),
+                    NavigationDestination(
+                      icon: Icon(Icons.chat_bubble_outline),
+                      selectedIcon: Icon(Icons.chat_bubble),
+                      label: "对话",
+                    ),
+                    NavigationDestination(
+                      icon: Icon(Icons.refresh_outlined),
+                      selectedIcon: Icon(Icons.refresh),
+                      label: "复习",
+                    ),
+                    NavigationDestination(
+                      icon: Icon(Icons.person_outline),
+                      selectedIcon: Icon(Icons.person),
+                      label: "我的",
+                    ),
+                  ],
+                )
+              : null,
+        ),
       ),
     );
   }
@@ -154,10 +234,14 @@ class _LearningShellState extends State<LearningShell> {
       case AppTab.home:
         return HomePage(
           state: widget.state,
-          onStartPrimaryTask: widget.state.reviewIsPrimary
-              ? () => showTab(AppTab.review)
-              : showLesson,
-          onOpenDialogue: showDialogue,
+          onStartPrimaryTask: () {
+            if (widget.state.reviewIsPrimary) {
+              showTab(AppTab.review);
+            } else {
+              showLesson();
+            }
+          },
+          onOpenDialogue: showDialogueScene,
           onResumeLessonDialogue: () => showDialogue(inLesson: true),
         );
       case AppTab.learn:
@@ -220,19 +304,19 @@ class _LearningMap extends StatelessWidget {
     return AppPage(
       child: SpacedColumn(
         children: [
-          const Eyebrow('学习地图 · 按掌握状态推进'),
-          Text('从认识到开口', style: Theme.of(context).textTheme.headlineMedium),
-          const Text('每节课都围绕一个能完成的小任务。'),
+          const Eyebrow("学习地图 · 按掌握状态推进"),
+          Text("从认识到开口", style: Theme.of(context).textTheme.headlineMedium),
+          const Text("每节课都围绕一个能完成的小任务。"),
           if (state.reviewBacklog)
             SectionCard(
               tint: AppColors.warm,
               child: SpacedColumn(
                 children: [
                   Text(
-                    '复习已有积压，今天先完成 ${state.dueReviewCount} 项到期复习，再开启新课。',
+                    "复习已有积压，今天先完成 ${state.dueReviewCount} 项到期复习，再开启新课。",
                     style: const TextStyle(color: AppColors.warmInk),
                   ),
-                  SecondaryButton(label: '先去复习', onPressed: onOpenReview),
+                  SecondaryButton(label: "先去复习", onPressed: onOpenReview),
                 ],
               ),
             ),
@@ -267,13 +351,13 @@ class _LearningMap extends StatelessWidget {
                       crossAxisAlignment: CrossAxisAlignment.start,
                       children: [
                         Text(
-                          '第 ${lesson.number} 课 · ${lesson.title}',
+                          "第 ${lesson.number} 课 · ${lesson.title}",
                           style: const TextStyle(fontWeight: FontWeight.w600),
                         ),
                         const SizedBox(height: 3),
                         Text(
                           lesson.segments.length > 1
-                              ? '${lesson.outcome} · 小段 ${lesson.segments.where((segment) => state.isSegmentComplete(segment.id)).length}/${lesson.segments.length}'
+                              ? "${lesson.outcome} · 小段 ${lesson.segments.where((segment) => state.isSegmentComplete(segment.id)).length}/${lesson.segments.length}"
                               : lesson.outcome,
                           style: Theme.of(context).textTheme.bodyMedium,
                         ),
@@ -289,12 +373,12 @@ class _LearningMap extends StatelessWidget {
               child: SpacedColumn(
                 children: [
                   const Text(
-                    'A0 巩固变式',
+                    "A0 巩固变式",
                     style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
                   ),
-                  const Text('换一个人物、地点或情境，继续巩固尚未稳定的核心表达。'),
+                  const Text("换一个人物、地点或情境，继续巩固尚未稳定的核心表达。"),
                   PrimaryButton(
-                    label: '安排一题巩固练习',
+                    label: "安排一题巩固练习",
                     onPressed: onStartReinforcement,
                   ),
                 ],