feat(category): 新增分类功能并重构相关屏幕

- 新增 CategoryScreen 屏幕用于显示分类- 新增 ItemCategory 模型类用于分类数据管理
- 新增 ItemCategoryRepository 用于分类数据持久化
- 新增 item_category_table 创建分类表结构
-重构 HomeScreen 底部导航栏，增加分类选项
- 重命名相关屏幕文件，统一命名规范
- 调整 ItemScreen 以适应新增的分类功能- 更新 SQLiteHelper 以支持分类表创建和默认分类插入
- 删除 StatisticsScreen 屏幕

lib/database/item_category_table.dart

@@ -0,0 +1,13 @@
+const String createItemCategoryTable = '''
+CREATE TABLE item_category (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  name TEXT NOT NULL,
+  description TEXT,
+  created_at TEXT DEFAULT (datetime('now')),
+  updated_at TEXT DEFAULT (datetime('now'))
+);
+''';
+
+const String insertDefaultCategory = '''
+INSERT INTO item_category (name, description) VALUES ('默认分类', '系统默认分类');
+''';

lib/database/sqlite_helper.dart

@@ -3,6 +3,8 @@ import 'package:sqflite/sqflite.dart';
 import 'package:path/path.dart';
 import 'package:path_provider/path_provider.dart';
 
+import 'item_category_table.dart';
+
 class DatabaseHelper {
   // 数据库名称
   static final _databaseName = "my_database.db";
@@ -35,5 +37,7 @@ class DatabaseHelper {
 
   Future<void> _onCreate(Database db, int version) async {
     await db.execute(createItemTable);
+    await db.execute(createItemCategoryTable);
+    await db.execute(insertDefaultCategory);
   }
 }

lib/models/item_category_model.dart

@@ -0,0 +1,54 @@
+class ItemCategory {
+  final int? id;
+  final String name;
+  final String? description;
+  final String? createdAt;
+  final String? updatedAt;
+
+  ItemCategory({
+    this.id,
+    required this.name,
+    this.description,
+    this.createdAt,
+    this.updatedAt,
+  });
+
+  // fromMap — 数据库 map -> Dart 对象
+  factory ItemCategory.fromMap(Map<String, dynamic> map) {
+    return ItemCategory(
+      id: map['id'] as int?,
+      name: map['name'] as String,
+      description: map['description'] as String?,
+      createdAt: map['created_at'] as String?,
+      updatedAt: map['updated_at'] as String?,
+    );
+  }
+
+  // toMap — Dart 对象 -> 数据库 map
+  Map<String, dynamic> toMap() {
+    return {
+      'id': id,
+      'name': name,
+      'description': description,
+      'created_at': createdAt,
+      'updated_at': updatedAt,
+    };
+  }
+
+  // copyWith — 方便局部更新
+  ItemCategory copyWith({
+    int? id,
+    String? name,
+    String? description,
+    String? createdAt,
+    String? updatedAt,
+  }) {
+    return ItemCategory(
+      id: id ?? this.id,
+      name: name ?? this.name,
+      description: description ?? this.description,
+      createdAt: createdAt ?? this.createdAt,
+      updatedAt: updatedAt ?? this.updatedAt,
+    );
+  }
+}

lib/models/item_model.dart

@@ -1,4 +1,4 @@
-import 'package:item_tracker/screens/item_screens/add_item_screen.dart';
+import 'package:item_tracker/screens/item_screens/item_screen.dart';
 
 class Item {
   int? id;

lib/repository/item_category_repository.dart

@@ -0,0 +1,57 @@
+import 'package:sqflite/sqflite.dart';
+
+import '../models/item_category_model.dart';
+
+class ItemCategoryRepository {
+  final Database db;
+
+  ItemCategoryRepository(this.db);
+
+  // 插入 (Create)
+  Future<int> insert(ItemCategory category) async {
+    return await db.insert(
+      'item_category',
+      category.toMap(),
+      conflictAlgorithm: ConflictAlgorithm.replace,
+    );
+  }
+
+  // 查询全部 (Read All)
+  Future<List<ItemCategory>> getAll() async {
+    final List<Map<String, dynamic>> maps = await db.query('item_category');
+    return maps.map((map) => ItemCategory.fromMap(map)).toList();
+  }
+
+  // 查询单个 (Read One by id)
+  Future<ItemCategory?> getById(int id) async {
+    final List<Map<String, dynamic>> maps = await db.query(
+      'item_category',
+      where: 'id = ?',
+      whereArgs: [id],
+      limit: 1,
+    );
+    if (maps.isNotEmpty) {
+      return ItemCategory.fromMap(maps.first);
+    }
+    return null;
+  }
+
+  // 更新 (Update)
+  Future<int> update(ItemCategory category) async {
+    return await db.update(
+      'item_category',
+      category.toMap(),
+      where: 'id = ?',
+      whereArgs: [category.id],
+    );
+  }
+
+  // 删除 (Delete)
+  Future<int> delete(int id) async {
+    return await db.delete(
+      'item_category',
+      where: 'id = ?',
+      whereArgs: [id],
+    );
+  }
+}

lib/screens/category_screens/category_screen.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+
+class CategoryScreen extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    const items = 20;
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('分类'),
+      ),
+      body: LayoutBuilder(
+        builder: (context, constraints) {
+          return SingleChildScrollView(
+            child: ConstrainedBox(
+              constraints: BoxConstraints(minHeight: constraints.maxHeight),
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                crossAxisAlignment: CrossAxisAlignment.stretch,
+                children: List.generate(
+                  items,
+                  (index) => ItemWidget(text: 'Item $index'),
+                ),
+              ),
+            ),
+          );
+        },
+      ),
+    );
+  }
+}
+
+class ItemWidget extends StatelessWidget {
+  const ItemWidget({super.key, required this.text});
+
+  final String text;
+
+  @override
+  Widget build(BuildContext context) {
+    return Card(child: SizedBox(height: 100, child: Center(child: Text(text))));
+  }
+}

lib/screens/home_screen.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
-import 'package:item_tracker/screens/item_list_screen.dart';
-import 'package:item_tracker/screens/statistics_screen.dart';
+import 'package:item_tracker/screens/category_screens/category_screen.dart';
+import 'package:item_tracker/screens/item_screens/item_list_screen.dart';
 import 'package:item_tracker/screens/my_screen.dart'; // 新增导入
 
 class HomeScreen extends StatefulWidget {
@@ -12,7 +12,7 @@ class _HomeScreenState extends State<HomeScreen> {
   int _selectedIndex = 0;
   static List<Widget> _widgetOptions = <Widget>[
     ItemListScreen(), 
-    StatisticsScreen(),
+    CategoryScreen(),
     MyScreen(),
   ];
 
@@ -37,6 +37,10 @@ class _HomeScreenState extends State<HomeScreen> {
             icon: Icon(Icons.add_business_sharp),
             label: '首页',
           ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.add_business_sharp),
+            label: '分类',
+          ),
           BottomNavigationBarItem(
             icon: Icon(Icons.person),
             label: '我的',

lib/screens/item_screens/item_list_screen.dart

@@ -1,10 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:item_tracker/provider/item_provider.dart';
-import 'package:item_tracker/screens/item_screens/add_item_screen.dart';
+import 'package:item_tracker/screens/item_screens/item_screen.dart';
 import 'package:provider/provider.dart';
 
-import 'item_screens/detail_item_screen.dart';
-
 class ItemListScreen extends StatefulWidget {
   @override
   _ItemListScreenState createState() => _ItemListScreenState();
@@ -52,7 +50,7 @@ class _ItemListScreenState extends State<ItemListScreen> {
                       Navigator.push(
                         context,
                         MaterialPageRoute(
-                          builder: (context) => AddItemScreen(itemToEdit: item),
+                          builder: (context) => ItemScreen(itemToEdit: item, ),
                         ),
                       );
                     },
@@ -63,7 +61,7 @@ class _ItemListScreenState extends State<ItemListScreen> {
         onPressed: () async {
           final shouldRefresh = await Navigator.push(
             context,
-            MaterialPageRoute(builder: (context) => AddItemScreen()),
+            MaterialPageRoute(builder: (context) => ItemScreen()),
           );
 
           print('shouldRefresh${shouldRefresh}');

lib/screens/item_screens/item_screen.dart

@@ -40,18 +40,16 @@ extension ItemIsUseX on ItemIsUse {
   }
 }
 
-class AddItemScreen extends StatefulWidget {
+class ItemScreen extends StatefulWidget {
   final Item? itemToEdit;
 
-  const AddItemScreen({Key? key, this.itemToEdit}) : super(key: key);
+  const ItemScreen({Key? key, this.itemToEdit}) : super(key: key);
 
   @override
   _FromTestRouteSate createState() => _FromTestRouteSate();
-
-
 }
 
-class _FromTestRouteSate extends State<AddItemScreen> {
+class _FromTestRouteSate extends State<ItemScreen> {
   String _name = '';
   String _description = '';
   String _location = '';
@@ -126,7 +124,8 @@ class _FromTestRouteSate extends State<AddItemScreen> {
                 },
               ),
               SizedBox(height: 28.0),
-              SubmitButton(onPressed: () {
+              SubmitButton(
+                  onPressed: () {
                     if (_formKey.currentState!.validate()) {
                       final newItem = Item(
                         name: _name,
@@ -151,7 +150,8 @@ class _FromTestRouteSate extends State<AddItemScreen> {
                       // 确保只有在表单验证成功后才调用 Navigator.pop
                       Navigator.pop(context, true);
                     }
-              })
+                  },
+                  isEdit: widget.itemToEdit != null)
             ],
           ),
         );

lib/screens/item_screens/widgets/item_is_use_selector.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
 
-import '../add_item_screen.dart';
+import '../item_screen.dart';
 
 class ItemIsUseSelector extends StatelessWidget {
   final ItemIsUse? selected;

lib/screens/item_screens/widgets/submit_button.dart

@@ -2,15 +2,18 @@ import 'package:flutter/material.dart';
 
 class SubmitButton extends StatelessWidget {
   final VoidCallback onPressed;
-  const SubmitButton({required this.onPressed});
+  final bool isEdit;
+
+  const SubmitButton({required this.onPressed, this.isEdit = false});
 
   @override
   Widget build(BuildContext context) {
+    final buttonText = isEdit ? '保存' : '提交';
     return ElevatedButton(
       onPressed: onPressed,
       child: Padding(
         padding: const EdgeInsets.all(16.0),
-        child: Text('提交'),
+        child: Text('${buttonText}'),
       ),
       style: ElevatedButton.styleFrom(
         shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),

lib/screens/statistics_screen.dart

@@ -1,15 +0,0 @@
-import 'package:flutter/material.dart';
-
-class StatisticsScreen extends StatelessWidget {
-  @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text('统计信息'),
-      ),
-      body: Center(
-        child: Text('这里将显示统计信息'),
-      ),
-    );
-  }
-}