Flutter Chat GPT：使用 flutter_chat_ui 实现聊天机器人

import 'package:flutter/material.dart';
import 'package:flutter_chat_ui/flutter_chat_ui.dart';
import 'package:flutter_chat_types/flutter_chat_types.dart' as types;
import 'package:file_picker/file_picker.dart';
import 'package:http/http.dart' as http;
import 'package:muse_nepu_course/home.dart';
import 'package:uuid/uuid.dart';
import 'package:path_provider/path_provider.dart';
import 'package:mime/mime.dart';
import 'package:flutter/services.dart' show rootBundle;
import 'dart:convert';
import 'dart:io';
import 'package:image_picker/image_picker.dart';

class chat_gpt extends StatefulWidget {
  @override
  _chat_gptState createState() => _chat_gptState();
}

class _chat_gptState extends State<chat_gpt> {
  List<types.Message> _messages = [];
  final _user = const types.User(
    id: '82091008-a484-4a89-ae75-a22bf8d6f3ac',
  );
  var _filteredStringList = [];
  var _stringList = [];
  //从assets/prompts.json中读取数据,并转换为List<Map<String, String>>
  void loadprompts() {
    String prompt = rootBundle.loadString('assets/prompts.json').toString();
    _stringList = json.decode(prompt);
    _filteredStringList = List.from(_stringList);
  }

  int _selectedIndex = -1;
  @override
  void initState() {
    super.initState();
    _loadMessages();
  }

  void _onSearch(String keyword) {
    setState(() {
      _filteredStringList = _stringList.where((item) {
        return item['act']!.contains(keyword) ||
            item['prompt']!.contains(keyword);
      }).toList();
    });
  }

  @override
  Widget build(BuildContext context) {
    loadprompts();
    return Scaffold(
      appBar: AppBar(
        title: Text('Chat with GPT'),
        //加入返回按鈕
        leading: IconButton(
          icon: Icon(Icons.arrow_back),
          onPressed: () {
            //跳转到成绩页面
            Navigator.push(context, MaterialPageRoute(builder: (context) {
              return HomePage();
            }));
          },
        ),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.settings),
            onPressed: () {
              showDialog(
                  context: context,
                  builder: (context) {
                    return Scaffold(
                        appBar: AppBar(
                          title: Text('自动注入'),
                          actions: [
                            IconButton(
                              icon: const Icon(Icons.search),
                              onPressed: () {
                                showSearch(
                                    context: context,
                                    delegate: _SearchBarDelegate(
                                        onSearch: _onSearch));
                              },
                            ),
                          ],
                        ),
                        body: ListView.builder(
                          itemCount: _filteredStringList.length,
                          itemBuilder: (BuildContext context, int index) {
                            String act = _filteredStringList[index]['act']!;  // 替换 " 为 '
                            String prompt = _filteredStringList[index]['prompt']!;  // 替换 " 为 '
                            return RadioListTile(
                              title: Text('行为: $act'),
                              subtitle: Text('语句: $prompt'),
                              value: index,
                              groupValue: _selectedIndex,
                              onChanged: (int? value) {
                                setState(() {
                                  _selectedIndex = value!;  // 替换 " 为 '
                                });
                              },
                            );
                          },
                        ));
                  });
            },
          ),
        ],
      ),
      body: Chat(
        messages: _messages,
        onAttachmentPressed: _handleAttachmentPressed,
        onMessageTap: _handleMessageTap,
        onPreviewDataFetched: _handlePreviewDataFetched,
        onSendPressed: _handleSendPressed,
        showUserAvatars: true,
        showUserNames: true,
        user: _user,
      ),
    );
  }

  void _addMessage(types.Message message) {
    setState(() {
      _messages.insert(0, message);
    });
  }

  void _handleAttachmentPressed() {
    showModalBottomSheet<void>(
      context: context,
      builder: (BuildContext context) => SafeArea(
        child: SizedBox(
          height: 144,
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              TextButton(
                onPressed: () {
                  Navigator.pop(context);
                  _handleImageSelection();
                },
                child: const Align(
                  alignment: AlignmentDirectional.centerStart,
                  child: Text('Photo'),
                ),
              ),
              TextButton(
                onPressed: () {
                  Navigator.pop(context);
                  _handleFileSelection();
                },
                child: const Align(
                  alignment: AlignmentDirectional.centerStart,
                  child: Text('File'),
                ),
              ),
              TextButton(
                onPressed: () => Navigator.pop(context),
                child: const Align(
                  alignment: AlignmentDirectional.centerStart,
                  child: Text('Cancel'),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  void _handleFileSelection() async {
    final result = await FilePicker.platform.pickFiles(
      type: FileType.any,
    );

    if (result != null && result.files.single.path != null) {
      final message = types.FileMessage(
        author: _user,
        createdAt: DateTime.now().millisecondsSinceEpoch,
        id: const Uuid().v4(),
        mimeType: lookupMimeType(result.files.single.path!),
        name: result.files.single.name,
        size: result.files.single.size,
        uri: result.files.single.path!,
      );

      _addMessage(message);
    }
  }

  void _handleImageSelection() async {
    final result = await ImagePicker().pickImage(
      imageQuality: 70,
      maxWidth: 1440,
      source: ImageSource.gallery,
    );

    if (result != null) {
      final bytes = await result.readAsBytes();
      final image = await decodeImageFromList(bytes);

      final message = types.ImageMessage(
        author: _user,
        createdAt: DateTime.now().millisecondsSinceEpoch,
        height: image.height.toDouble(),
        id: const Uuid().v4(),
        name: result.name,
        size: bytes.length,
        uri: result.path,
        width: image.width.toDouble(),
      );

      _addMessage(message);
    }
  }

  void _handleMessageTap(BuildContext _, types.Message message) async {
    if (message is types.FileMessage) {
      var localPath = message.uri;

      if (message.uri.startsWith('http')) {
        try {
          final index =
              _messages.indexWhere((element) => element.id == message.id);
          final updatedMessage =
              (_messages[index] as types.FileMessage).copyWith(
            isLoading: true,
          );

          setState(() {
            _messages[index] = updatedMessage;
          });

          final client = http.Client();
          final request = await client.get(Uri.parse(message.uri));
          final bytes = request.bodyBytes;
          final documentsDir = (await getApplicationDocumentsDirectory()).path;
          localPath = '$documentsDir/${message.name}';

          if (!File(localPath).existsSync()) {
            final file = File(localPath);
            await file.writeAsBytes(bytes);
          }
        } finally {
          final index =
              _messages.indexWhere((element) => element.id == message.id);
          final updatedMessage =
              (_messages[index] as types.FileMessage).copyWith(
            isLoading: null,
          );

          setState(() {
            _messages[index] = updatedMessage;
          });
        }
      }
    }
  }

  void _handlePreviewDataFetched(
    types.TextMessage message,
    types.PreviewData previewData,
  ) {
    final index = _messages.indexWhere((element) => element.id == message.id);
    final updatedMessage = (_messages[index] as types.TextMessage).copyWith(
      previewData: previewData,
    );

    setState(() {
      _messages[index] = updatedMessage;
    });
  }

  void _handleSendPressed(types.PartialText message) {
    final textMessage = types.TextMessage(
      author: _user,
      createdAt: DateTime.now().millisecondsSinceEpoch,
      id: const Uuid().v4(),
      text: message.text,
    );

    _addMessage(textMessage);
    print(message.text);
    //打印最近20条消息
    print(_messages.sublist(0, 20));
  }

  void _loadMessages() async {
    final response = await rootBundle.loadString('assets/messages.json');
    final messages = (jsonDecode(response) as List)
        .map((e) => types.Message.fromJson(e as Map<String, dynamic>))
        .toList();

    setState(() {
      _messages = messages;
    });
  }
}

class _SearchBarDelegate extends SearchDelegate<String> {
  final Function(String) onSearch;

  _SearchBarDelegate({required this.onSearch});

  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: const Icon(Icons.clear),
        onPressed: () {
          query = '';
        },
      ),
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: const Icon(Icons.arrow_back),
      onPressed: () {
        close(context, '');
      },
    );
  }

  @override
  Widget buildResults(BuildContext context) {
    onSearch(query);
    return const SizedBox.shrink();
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    return const SizedBox.shrink();
  }
}

这个错误是由于在 initState 中调用了 setState 导致的，尝试将 loadprompts 移到 build 中调用，或者将 loadprompts 改为同步调用即可解决此问题。例如：将 loadprompts 中的 await 去掉，改为直接读取即可。