feat:增加待办排序UI功能

lib/models/todo.dart

@@ -111,3 +111,5 @@ enum TodoTab {
 
   const TodoTab(this.label);
 }
+
+enum TodoSortMode { time, priority }

lib/pages/todo_page.dart

@@ -26,6 +26,7 @@ class TodoPageState extends State<TodoPage> {
 
   late List<Todo> _todos;
   TodoTab _currentTab = TodoTab.active;
+  late TodoSortMode _selectedMode = TodoSortMode.time;
 
   // 获取过滤后的待办事项
   List<Todo> get _activeTodos => getActiveTodos(_currentTab, _todos);
@@ -37,7 +38,13 @@ class TodoPageState extends State<TodoPage> {
   @override
   void initState() {
     super.initState();
-    _todos = todoService.getAllTodos();
+    _refreshTodos();
+  }
+
+  void _refreshTodos() {
+    setState(() {
+      _todos = todoService.getAllTodos(_selectedMode);
+    });
   }
 
   @override
@@ -45,6 +52,7 @@ class TodoPageState extends State<TodoPage> {
     return Column(
       children: [
         _buildTodoTabs(),
+        _buildTodoSegment(),
         Expanded(child: _buildActiveTodoList(context)),
       ],
     );
@@ -62,6 +70,36 @@ class TodoPageState extends State<TodoPage> {
     );
   }
 
+  Widget _buildTodoSegment() {
+    final colors = Theme.of(context).colorScheme;
+
+    return SegmentedButton<TodoSortMode>(
+      showSelectedIcon: false,
+      emptySelectionAllowed: false,
+      multiSelectionEnabled: false,
+      segments: [
+        ButtonSegment<TodoSortMode>(
+          value: TodoSortMode.time,
+          icon: Icon(Icons.access_time_filled, size: 16),
+          label: const Text('时间', style: TextStyle(fontSize: 12)),
+        ),
+        ButtonSegment<TodoSortMode>(
+          value: TodoSortMode.priority,
+          icon: Icon(Icons.flag_outlined, size: 16,),
+          label: const Text('优先级', style: TextStyle(fontSize: 12)),
+        ),
+      ],
+      selected: {_selectedMode},
+      onSelectionChanged: (Set<TodoSortMode> newSelection) {
+        setState(() {
+          _selectedMode = newSelection.first;
+        });
+        _refreshTodos();
+      },
+      style: buildSegmentStyle(colors),
+    );
+  }
+
   Widget _buildActiveTodoList(BuildContext context) {
     return _activeTodos.isEmpty
         ? buildEmptyState(context, _currentTab)
@@ -142,9 +180,7 @@ class TodoPageState extends State<TodoPage> {
       );
     }
 
-    setState(() {
-      _todos = todoService.getAllTodos();
-    });
+    _refreshTodos();
 
     if (isSuccess) {
       showSuccessDialog(context, isEditing ? '更新成功' : '添加成功');
@@ -157,9 +193,7 @@ class TodoPageState extends State<TodoPage> {
     await notifyService.cancelNotification(todo.id);
     bool isSuccess = await todoService.deleteTodo(todo);
 
-    setState(() {
-      _todos = todoService.getAllTodos();
-    });
+    _refreshTodos();
 
     if (isSuccess) {
       showSuccessDialog(context, '删除成功');

lib/service/todo_service.dart

@@ -15,9 +15,29 @@ class TodoService {
     }
   }
 
-  List<Todo> getAllTodos() {
-    return box.values.toList()
-      ..sort((a, b) => b.updateTime.compareTo(a.updateTime));
+  List<Todo> getAllTodos(TodoSortMode mode) {
+    if (mode == TodoSortMode.time) {
+      return box.values.toList()
+        ..sort((a, b) {
+          // 先按是否有 dueDate 分组：有时间的排前面
+          if (a.dueDate != null && b.dueDate == null) {
+            return -1; // a有时间，b没有时间，a排在前面
+          } else if (a.dueDate == null && b.dueDate != null) {
+            return 1;  // a没有时间，b有时间，b排在前面
+          }
+          // 都有 dueDate，按 dueDate 排序
+          else if (a.dueDate != null && b.dueDate != null) {
+            return a.dueDate!.compareTo(b.dueDate!); // 最近的在前面
+          }
+          // 都没有 dueDate，按 updateTime 排序
+          else {
+            return b.updateTime.compareTo(a.updateTime); // 最近的在前面
+          }
+        });
+    } else {
+      return box.values.toList()
+        ..sort((a, b) => b.priorityIndex.compareTo(a.priorityIndex));
+    }
   }
 
   List<Todo> getAllTodosByYear(int year) {

lib/widgets/common.dart

@@ -213,6 +213,41 @@ Widget buildToggleSwitch<T extends Enum>({
   );
 }
 
+ButtonStyle buildSegmentStyle(ColorScheme colors) {
+  return ButtonStyle(
+    side: WidgetStateProperty.all<BorderSide>(
+      const BorderSide(color: Colors.transparent, width: 0),
+    ),
+    iconColor: WidgetStateProperty.resolveWith<Color>(
+          (Set<WidgetState> states) {
+        if (states.contains(WidgetState.selected)) {
+          return colors.onPrimary;
+        }
+        return Colors.grey;
+      },
+    ),
+    backgroundColor: WidgetStateProperty.resolveWith<Color>((
+        Set<WidgetState> states,
+        ) {
+      if (states.contains(WidgetState.selected)) {
+        return colors.primary;
+      }
+      return Colors.grey.shade200;
+    }),
+    foregroundColor: WidgetStateProperty.resolveWith<Color>((
+        Set<WidgetState> states,
+        ) {
+      if (states.contains(WidgetState.selected)) {
+        return colors.onPrimary;
+      }
+      return colors.onSurface;
+    }),
+    shape: WidgetStateProperty.all<RoundedRectangleBorder>(
+      RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),
+    ),
+  );
+}
+
 Widget circleIconButton({
   required IconData icon,
   required VoidCallback onPressed,