feat:更新待办事项对话框功能

lib/provider/app_provider.dart

@@ -1,11 +1,12 @@
 import 'package:flutter/material.dart';
 
-class AppProvider  with ChangeNotifier {
+class AppProvider with ChangeNotifier {
   int _currentIndex = 0;
+
   int get currentIndex => _currentIndex;
 
   void changeTab(int index) {
     _currentIndex = index;
     notifyListeners();
   }
-}
+}

lib/provider/todo_provider.dart

@@ -0,0 +1,21 @@
+import 'package:flutter/material.dart';
+import 'package:flisp_app/models/todo.dart';
+
+class TodoProvider with ChangeNotifier {
+  TodoItem _formItem = TodoItem.getEmpty();
+
+  TodoItem get formItem => _formItem;
+
+  void resetForm() {
+    _formItem = TodoItem.getEmpty();
+    notifyListeners();
+  }
+
+  void initForm(TodoItem todo) {
+    _formItem.title = todo.title;
+    _formItem.content = todo.content ?? '';
+    _formItem.dueDate = todo.dueDate;
+    _formItem.priority = todo.priority;
+    notifyListeners();
+  }
+}