update greeting

lib/screens/full_screen.dart

@@ -1,4 +1,7 @@
+import 'package:ai_chat_assistant/models/chat_message.dart';
+import 'package:basic_intl/intl.dart';
 import 'package:flutter/material.dart';
+import '../enums/message_status.dart';
 import '../widgets/chat_box.dart';
 import '../widgets/gradient_background.dart';
 import '../services/message_service.dart';
@@ -63,6 +66,14 @@ class _FullScreenState extends State<FullScreen> {
                     WidgetsBinding.instance.addPostFrameCallback((_) {
                       _scrollToBottom();
                     });
+                    final messageService = context.read<MessageService>();
+                    List<ChatMessage> fullScreenMessages = List.from(handler.messages);
+                    if (fullScreenMessages.isEmpty) {
+                      String text = Intl.getCurrentLocale().startsWith('zh')
+                          ? "您好，我是众众，请问有什么可以帮您？"
+                          : "Hi, I'm Zhongzhong, may I help you ? ";
+                      messageService.addMessage(text, false, MessageStatus.normal);
+                    }
                     return ChatBox(
                       scrollController: _scrollController,
                       messages: handler.messages,

lib/screens/part_screen.dart

@@ -17,10 +17,18 @@ class PartScreen extends StatefulWidget {
 
 class _PartScreenState extends State<PartScreen> {
   final ScrollController _scrollController = ScrollController();
+  bool _isInitialized = false;
 
   @override
   void initState() {
     super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      final messageService = Provider.of<MessageService>(context, listen: false);
+      messageService.initializeEmpty();
+      setState(() {
+        _isInitialized = true;
+      });
+    });
   }
 
   @override
@@ -54,6 +62,9 @@ class _PartScreenState extends State<PartScreen> {
       backgroundColor: Colors.transparent,
       body: LayoutBuilder(
         builder: (context, constraints) {
+          if (!_isInitialized) {
+            return const SizedBox.shrink();
+          }
           final double minHeight = constraints.maxHeight * 0.18;
           final double maxHeight = constraints.maxHeight * 0.4;
           final double chatWidth = constraints.maxWidth * 0.94;
@@ -74,9 +85,13 @@ class _PartScreenState extends State<PartScreen> {
                   child: GestureDetector(
                     behavior: HitTestBehavior.translucent,
                     onTap: () {
-                      Provider.of<MessageService>(context, listen: false)
-                          .abortReply();
+                      final messageService = context.read<MessageService>();
                       if (widget.onHide != null) widget.onHide!();
+                      setState(() {
+                        _isInitialized = true;
+                      });
+                      messageService.abortReply();
+                      messageService.initializeEmpty();
                     },
                     child: Container(
                       color: Colors.transparent,

lib/services/message_service.dart

@@ -34,16 +34,7 @@ class MessageService extends ChangeNotifier {
       TextClassificationService();
   final VehicleCommandService _vehicleCommandService = VehicleCommandService();
 
-  final List<ChatMessage> _messages = [
-    ChatMessage(
-        id: Uuid().v1(),
-        text: Intl.getCurrentLocale().startsWith('zh')
-            ? "您好，我是众众，请问有什么可以帮您？"
-            : "Hi, I'm Zhongzhong, may I help you ? ",
-        isUser: false,
-        timestamp: DateTime.now(),
-        status: MessageStatus.normal)
-  ];
+  final List<ChatMessage> _messages = [];
 
   List<ChatMessage> get messages => List.unmodifiable(_messages);
 
@@ -62,6 +53,11 @@ class MessageService extends ChangeNotifier {
 
   bool _isReplyAborted = true;
 
+  void initializeEmpty() {
+    _messages.clear();
+    notifyListeners();
+  }
+
   Future<void> startVoiceInput() async {
     if (await Permission.microphone.status == PermissionStatus.denied) {
       PermissionStatus status = await Permission.microphone.request();